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Conext™ CL Inverter

Conext CL 20000 EConext CL 25000 E

Solution Guide for Decentralized PV Systems Using Conext CL Inverters975-0747-01-01 Revision AJanuary 2015

solar.schneider-electric.com

Conext CL InverterConext CL 20000 EConext CL 25000 E

Solution Guide


Copyright © 2015 Schneider Electric. All Rights Reserved. All trademarks are owned by Schneider Electric Industries SAS or its affiliated companies.

Exclusion for DocumentationUNLESS SPECIFICALLY AGREED TO IN WRITING, SELLER

(A) MAKES NO WARRANTY AS TO THE ACCURACY, SUFFICIENCY OR SUITABILITY OF ANY TECHNICAL OR OTHER INFORMATION PROVIDED IN ITS MANUALS OR OTHER DOCUMENTATION;(B) ASSUMES NO RESPONSIBILITY OR LIABILITY FOR LOSSES, DAMAGES, COSTS OR EXPENSES, WHETHER SPECIAL, DIRECT, INDIRECT, CONSEQUENTIAL OR INCIDENTAL, WHICH MIGHT ARISE OUT OF THE USE OF SUCH INFORMATION. THE USE OF ANY SUCH INFORMATION WILL BE ENTIRELY AT THE USER’S RISK; AND

(C) REMINDS YOU THAT IF THIS MANUAL IS IN ANY LANGUAGE OTHER THAN ENGLISH, ALTHOUGH STEPS HAVE BEEN TAKEN TO MAINTAIN THE ACCURACY OF THE TRANSLATION, THE ACCURACY CANNOT BE GUARANTEED. APPROVED CONTENT IS CONTAINED WITH THE ENGLISH LANGUAGE VERSION WHICH IS POSTED AT SOLAR.SCHNEIDER-ELECTRIC.COM.

Document Number: 975-0747-01-01 Revision: Revision A Date: January 2015

Product Part Numbers:

Contact Information solar.schneider-electric.comPlease contact your local Schneider Electric Sales Representative at: http://solar.schneider-electric.com

Base: AC connector and DC connector PVSCL20E100 PVSCL25E100

Essential: Touch-safe fuse holder, DC switch, and AC connector

PVSCL20E200 PVSCL25E200

Essential+: Essential with MC4 connector PVSCL20E201 PVSCL25E201

Optimum: Essential + DC SPD and AC SPD PVSCL20E300 PVSCL25E300

Optimum+: Optimum with MC4 connector PVSCL20E301 PVSCL20E301

About This Guide

Purpose

The purpose of this Solution Guide is to provide explanations for designing a decentralized PV system using Conext and Balance of System (BOS) components. It describes the interfaces required to implement this architecture and gives rules to build the solution.

Scope

This Guide provides technical information and design recommendations. It explains the design requirements of each of the system components and provides details on how to choose the correct recommendations.

The information provided in this guide does not modify, replace, or waive any instruction or recommendations described in the product Installation and Owner’s Guides including warranties of Schneider Electric products. Always consult the Installation and Owner’s guides of a Schneider Electric product when installing and using that product in a decentralized PV system design using Conext CL inverters.

For help in designing a PV power plant contact your Schneider Electric Sales Representative or visit the Schneider Electric website for more information at solar.schneider-electric.com.

Audience

The Guide is intended for use by anyone who plans to construct or install a system involving the Conext CL Inverter. The information in this manual is intended for qualified personnel. Qualified personnel have training, knowledge, and experience in:

• Installing electrical equipment and PV power systems (up to 1000 V).

• Applying all applicable installation codes.

• Analyzing and reducing the hazards involved in performing electrical work.

• Selecting and using Personal Protective Equipment (PPE).

Organization

This Guide is organized into seven chapters.

Chapter 1, Introduction

Chapter 2, Decentralized PV Solutions

Chapter 3, DC System Design

Chapter 4, AC System Design

Chapter 5, Important Aspects of a Decentralized System Design

Chapter 6, Layout Optimization

Chapter 7, Frequently Asked Questions (FAQ)

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About This Guide

Related Information

You can find more information about Schneider Electric as well as its products and services at solar.schneider-electric.com.

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Important Safety Instructions

READ AND SAVE THESE INSTRUCTIONS - DO NOT DISCARD

This document contains important safety instructions that must be followed during installation procedures (if applicable). Read and keep this Solution Guide for future reference.

Read these instructions carefully and look at the equipment (if applicable) to become familiar with the device before trying to install, operate, service or maintain it. The following special messages may appear throughout this bulletin or on the equipment to warn of potential hazards or to call attention to information that clarifies or simplifies a procedure.

The addition of either symbol to a “Danger” or “Warning” safety label indicates that an electrical hazard exists which will result in personal injury if the instructions are not followed.

This is the safety alert symbol. It is used to alert you to potential personal injury hazards. Obey all safety messages that follow this symbol to avoid possible injury or death.

DANGER

DANGER indicates an imminently hazardous situation, which, if not avoided, will result in death or serious injury.

WARNING

WARNING indicates a potentially hazardous situation, which, if not avoided, can result in death or serious injury.

CAUTION

CAUTION indicates a potentially hazardous situation, which, if not avoided, can result in moderate or minor injury.

NOTICE

NOTICE indicates important information that you need to read carefully.

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DANGER

RISK OF FIRE, ELECTRIC SHOCK, EXPLOSION, AND ARC FLASH

This Solution Guide is in addition to, and incorporates by reference, the relevant product manuals for the Conext CL Inverter. Before reviewing this Solution Guide you must read the relevant product manuals. Unless specified, information on safety, specifications, installation, and operation is as shown in the primary documentation received with the products. Ensure you are familiar with that information before proceeding.

Failure to follow these instructions will result in death or serious injury.

DANGER

ELECTRICAL SHOCK AND FIRE HAZARD

Installation including wiring must be done by qualified personnel to ensure compliance with all applicable installation and electrical codes including relevant local, regional, and national regulations. Installation instructions are not covered in this Solution Guide but are included in the relevant product manuals for the Conext CL Inverter. Those instructions are provided for use by qualified installers only.


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Contents
1 IntroductionDecentralized Photovoltaic (PV) Architecture - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1–2About the Conext CL Inverter - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1–3Key Specifications of the Conext CL Inverter - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1–4Key Features of Wiring Box - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1–4

2 Decentralized PV SolutionsWhy Decentralize PV Solutions? - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–2

Drivers for decentralizing system design - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–2Benefits with Conext CL for a Decentralized System Design - - - - - - - - - - - - - - - - - - - - - - - - 2–3PV System Overview - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–4PV System - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–4PV System Design Using Conext CL Inverters - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–5Wiring Box selection - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–6

Selection criteria - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–6Building Blocks of a Decentralized PV Power Plant - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–9

Positioning Inverters - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–11Inverter location - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–11

Option 1 (Inverters installed next to PV modules) - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–12Option 2 (Inverters installed next to AC Combiner groups) - - - - - - - - - - - - - - - - - - - - - 2–13Option 3 (Inverters installed next to PV inverters without first-level AC Combiners) - - - - 2–14Option 4 (Inverters installed next to LV/MV transformer) - - - - - - - - - - - - - - - - - - - - - - - 2–15

3 DC System DesignDC System Design - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–2

String and Array Sizing Rules - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–2Number of PV Modules in the Series - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–2Minimum Number of PV Modules - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–3Maximum Number of PV Modules - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–4Number of PV Modules in Parallel - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–5

String Connections to Conext CL Inverter - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–5DC String Arrangement and Cable Sizing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–6

DC System Component Design - The DC Box - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–9Function - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–9Typical use - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–9Advantages of the offer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–10

4 AC System DesignAC System Design - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–2

Circuit Breaker Coordination - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–3Cascading or backup protection - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–3

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Contents

Discrimination - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–3AC Component Design - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–4

The AC Switch Box - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–5Function - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–5Typical use - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–5Advantages of the offer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–5AC Cable sizing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–6AC Combiner Box - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–7Function - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–8Typical use - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–8AC Re-Combiner Box - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–11Distribution control - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–14Function - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–15Typical use - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–15Recommended System Design - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–16System Technical Summary - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–16CB Protection – Discrimination tables for selection. - - - - - - - - - - - - - - - - - - - - - - - - - - 4–17

5 Important Aspects of a Decentralized System DesignSelection of Surge Protection device for Decentralize PV systems - - - - - - - - - - - - - - - - - - - - - - 5–2

Use of SPDs on DC circuits - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–2Use of SPD on AC Circuits in Decentralized PV systems - - - - - - - - - - - - - - - - - - - - - - - - - - 5–6

Grounding System Design for Decentralized PV systems - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–8General Understanding of Grounding - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–8Grounding for PV Systems - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–9Transformer selection for decentralize PV plants with Conext CL - - - - - - - - - - - - - - - - - - - - 5–11Monitoring System Design - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–12

Monitoring System Design: Commercial Rooftops and Small Ground Mounted Farms - - 5–12Grid Connection - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–17

Connecting to a Public LV network - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–17Role of Circuit Impedance in Parallel Operation of Multiple Conext CL String Inverters - - - - - - 5–19

6 Layout OptimizationLayout Design Rules - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6–2Layouts - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6–2

7 Frequently Asked Questions (FAQ)Safety Information - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7–2Frequently Asked Questions - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7–2

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Figures
Figure 1-1 Conext CL Inverter - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1–3Figure 1-2 Typical PV grid tied installation using CL Inverters - - - - - - - - - - - - - - - - - - - - - - - - - - 1–3Figure 2-1 PV System Overview- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–4Figure 2-2 Wiring box options (IEC only) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–8Figure 2-3 Standard Block Option 1 for a 1MW System - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–12Figure 2-4 Standard Block Option 2 for a 1MW System - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–13Figure 2-5 Standard Block Option 3 for a 1MW System - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–14Figure 2-6 Standard Block Option 4 for a 1MW System - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–15Figure 3-1 String arrangement and interconnection example with Landscape - - - - - - - - - - - - - - - 3–8Figure 3-2 String arrangement and interconnection example with Portrait oriented modules- - - - - 3–8Figure 3-3 DC Box Schematic Diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–10Figure 4-1 Summarizing Table- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–4Figure 4-2 AC Switch Box Schematic Diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–5Figure 4-3 AC Switch Box Schematic Diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–8Figure 4-4 Distribution Control Diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–15Figure 5-1 Installation of SPDs- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–5Figure 5-2 Type 2 SPDs - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–6Figure 5-3 Circuit of Internal SPD Connections - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–7Figure 5-4 TN-S Earthing System, 3-Phase + Neutral- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–7Figure 5-5 TN-C Earthing System, 3-Phase- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–8Figure 5-6 MEN Earthing System, 3-Phase - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–8Figure 5-7 Reverse Current - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–9Figure 5-8 Grounding Circuit Connections - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–10Figure 5-9 Remote monitoring of a 100kW plant (4X25kW Conext CL inverters) using InsightLink
feature of inverters - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–15Figure 5-10 Remote monitoring of a 625kW rooftop plant (25X25kW Conext CL inverters) using

Conext SmartBox-BA and Conext Insight portal - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–15Figure 5-11 Remote monitoring and control of a 5MW ground mounted plant (200X25kW

Conext CL inverters) using Conext SmartBox - ES in master-slave mode and Conext Insight portal - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–16

Figure 5-12 Generic AC Grid Connected Inverters Diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - 5–20

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Tables
Table 2-1 Decentralized PV System Blocks - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2–9Table 3-1 DC Box Component Reference - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3–10Table 4-1 AC Box Component Reference - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4–6Table 4-2 Percentage losses for Cu cable w.r.t maximum AC cable length - - - - - - - - - - - - - - - - 4–7Table 5-1 Power loss values for transformer ratings and impedance - - - - - - - - - - - - - - - - - - - - 5–11Table 7-1 De-rating for 500 Vdc and 800V, 230 Vac 25 Kw- - - - - - - - - - - - - - - - - - - - - - - - - - - - 7–5Table 7-2 De-rating for 350 Vdcand 800V, 230 Vac 20 Kw - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7–5
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1 Introduction

This introduction chapter contains information:• About the Conext CL Inverter• Decentralized Photovoltaic (PV)

Architecture• Key Specifications of the Conext CL

Inverter• Key Features of Wiring Box

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Introduction

Decentralized Photovoltaic (PV) Architecture Use of a decentralized PV Architecture

String inverters are typically decentralized over a PV plant, sometimes located under PV arrays, in order to facilitate array connections to the inverter.

Advantages of a decentralized PV architecture include:

• Easy adaptation of the solution to roof or plant specificities

• Easy installation of the inverters on roof or plant

• Easy electrical protection

• Easy connection to the grid

• Easy monitoring

• Reduced system downtime which means greater energy yield

• Easy swapping of units that need servicing

Use of a Three Phase String Conext CL Inverter

The new Conext CL 20000 E and CL 25000 E grid-tie three phase string inverters are suited for outdoor use and are the ideal solution for commercial buildings, carports and decentralized power plants in multiple megawatt (MW) ranges. With their modular design and two wide input range Maximum Power Point Trackers (MPPTs), these inverters are very flexible and therefore easy to install.

WARNING

ELECTRICAL SHOCK HAZARD

• The Conext CL Inverters are transformerless inverters, suited for use with PV modules that do not require the grounding of a DC polarity.

• In case of a “net metering” grid connection type, connection has to be adapted to the local rules specified by the utilities.

• Always refer to national and local installation and electrical codes in designing a power system.

Failure to follow these instruction can result in death or serious injury.

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About the Conext CL Inverter

About the Conext CL Inverter

The Conext CL Inverter is a three phase transformerless string inverter designed for high efficiency, easy installation, and maximum yield. The inverter converts the solar electric (photovoltaic or PV) power into utility grade electricity that can be used for commercial or utility applications. The inverter is designed to collect maximum available energy from the PV array by constantly adjusting its output power to track maximum power point (MPP) of the PV array. The inverter has two MPPT channels (MPPT1 and MPPT2). A maximum of four string inputs can be connected to each independent MPPT channel. The two independent PV arrays can operate at different peak power points to capture the maximum possible energy. The inverter accommodates PV arrays with open circuit voltages up to 1000 VDC. The CL Inverter is designed to be transformerless and therefore, has no galvanic isolation.

Figure 1-1 Conext CL Inverter

Figure 1-2 Typical PV grid tied installation using CL Inverters

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Introduction

Key Specifications of the Conext CL Inverter• Conext CL 20000 E inverter: 20 kVA (1000 VDC systems)

• Conext CL 25000 E inverter: 25 kVA (1000 VDC systems)

• PV compatibility: Designed to work with Mono-Crystalline or Poly-Crystalline panel

• Three-phase (3-Phase + N + PE [ground]), four-wire, grid-tie, transformerless

• Wide MPPT voltage range

• 350–800 VDC for 20 KVA

• 430–800 VDC for 25 KVA

• Supports high array to inverter ratio

• Two independent MPPTs with the option for combined MPPT operation

• Up to 60% to 40% unbalanced MPPT operation capability

• Energy harvest efficiency (MPPT): >99%

• Fast sweep MPPT tracking

• Maximum power conversion efficiency: >98%

• Power factor adjustment range: 0.8 capacitive to 0.8 inductive

• Low AC output current distortion (THD < 3%) @ nominal power

• IP65 (electronics)/IP54 (rear portion) protection class for installation in outdoor environments

• –25 to 60 °C operating temperature range

• Flexible installation: Inverter and wiring box can be installed separately

• Dry Contact (Multi-function) relay

• Remote Power Off (RPO)

• Modbus RS485 and Modbus TCP communications

• USB device host for local firmware upgrade

• Custom data logging (user configurable)

• 3” (diagonally) graphical display (LCD) with integrated seven-button control panel

• Embedded Web server via Ethernet (TCP/IP)

• Sunspec Alliance Modbus map offering

Key Features of Wiring Box• Integrated DC switch

• Touch safe fuse holder for PV string protection

• AC and DC Surge Protection (SPD) and Monitoring

• Bottom cable entry for easy installation

• Tool free AC cable termination using spring connector

• Tool free DC cable termination using MC4 connectors (Optional)

1–4 975-0747-01-01 Revision A

2 Decentralized PV Solutions

This chapter on decentralized PV solutions contains the following information.• Drivers for decentralizing system

design• Benefits with Conext CL for a

Decentralized System Design• PV System Overview• PV System• PV System Design Using Conext CL

Inverters• Wiring Box selection• Building Blocks of a Decentralized PV

Power Plant• Inverter location

975-0747-01-01 Revision A 2–1

Decentralized PV Solutions

Why Decentralize PV Solutions?

Drivers for decentralizing system design

1. Lower cost of installation and easy to install

• Smaller units have lighter weight and easier to handle

• Inverters can be mounted directly on/underneath the photovoltaic (PV) mounting structures

• Product is easy and inexpensive to ship and can be installed by two installers versus central inverters which are typically very heavy and expensive to transport/install (a crane is often required)

• No concrete mounting pad required: unit mounted directly to wall, pole or PV frame racks

• Cost effective: No need to use a PV Box on roof or on ground for inverters

2. Easy to service and increased energy harvest

• If the inverter detects a failure event, only part of the field is affected versus a large portion of the field when a large central inverter is used, which means greater return on investment (ROI)

• Multiple MPPTs to allow greater installation flexibility and increased PV harvest compared to single central inverters

3. Easy electrical protection

• DC circuit remains limited to the roof, without penetrating into the building; DC cabling remaining “alive” is restricted

• AC circuit is enlarged, requiring additional AC equipment which are typically less expensive and more readily available

• Fire situation management is simplified and fireman safety is improved

4. Easy adaptation to roof specificities

• Ability to support different roof pan orientations

• Heterogeneous layout of the strings is facilitated (unbalanced arrays)

• Obstacles on roofs and shadowing/shading have less production impact

5. Easy connection to the grid

• Small 3-Phase inverters can be configured in parallel directly to the grid

6. Easy monitoring

• Monitoring at much granular level about production areas

• Performance ratio calculations and fault detection can be reached at a reduced cost

2–2 975-0747-01-01 Revision A


Benefits with Conext CL for a Decentralized System Design

• 5 wiring box options to fit different needs

• Wall, pole and lay flat mounting

• Easy to connect to 3rd party monitoring

• Full grid management features

High flexibility

• Light and 2 person installation

• Separate inverter and wiring box

• Touch safe fuse holder

• Conext CL EasyConfig tool

Easy to install and service

• 98.3% peak efficiency, 98% Euro efficiency

• Eliminate cost of external DC combiner box

• 2 MPPT and shade tolerant MPPT algorithm

• High over paneling capability

Higher ROI

• Electrolyte free design

• Strict DFQ/DFR process

• Rigorous MEOST, HALT and THB tests

• Manufacturing in Leading SE facility

Designed for reliability

975-0747-01-01 Revision A 2–3


PV System Overview

PV System

PV system modeling are:

• Site conditions

• Type of system

• Losses

Site conditions

It is very important to interpret site conditions carefully and model the exact conditions in PV system design software. These conditions include shadow from surroundings, ground slope, layout boundary conditions, rain water catchment area, PV module string arrangements, shape of the layout, obstacles like power lines, gas pipelines, rivers, archaeological conditions, and similar obstacles.

Once all possible factors affecting the PV system design are listed and assessed, capacity of selected PV installation site can be determined for further processing. Government agency permits and statutory clearances also depend on these factors. Cost of the land and overall PV system varies with respect to these conditions.

Figure 2-1 PV System Overview

2–4 975-0747-01-01 Revision A


System

PV system installation can be grid tied or stand alone. It could be on the roof, ground-mounted with tracking option, or it could be in a car park or facade-mounted.

Modelling of system has to be considered using the most suitable option or may be the main purpose of installation.

Quantum and usage of generated electricity is a very important factor deciding the type of system. A good system design has high efficiency, flexibility and modular approach for faster and quicker installations.

Selection of major components like PV modules, inverters and mounting structures comprises the most part of system modelling and design. These three components also affect the cost, output, and efficiency of the system.

Losses

Any PV system has two major types of losses. Losses associated with meteorological factors and losses due to system components.

A carefully modelled PV system represents both types of losses very accurately and realistically. It is very difficult to consider this but PV system modelling should take care of each aspect of design and component to simulate the scenario which represents the actual conditions very closely.

PV System Design Using Conext CL Inverters

In order to facilitate the users, the Conext CL inverter’s latest dataset and system component file is available with widely used modeling software and databases. These files are also available for download on the Schneider Electric solar web portal.

Schneider Electric suggests the following points to consider during system design using Conext CL inverters.

• Using well defined standard system Blocks

• Optimized PV system design using standard components

• Cost competitiveness

• Designed for quick installation

Both rooftop and ground mount systems can be modeled and designed using standard system blocks comprising of Conext CL inverters and user defined PV modules and mounting solution.

A block of 250kW for rooftop solutions and 1000kW for ground mount solutions can be considered to multiply several times to achieve the required capacity. Smaller size of standard blocks like 100kW, can be defined in order to fit the requirement of the user. A standard block is designed once for all respective components and repeated several times in the installation. It reduces the efforts and time to design the complete solution and increases the flexibility and speed of construction. Manufacturing of components also becomes quicker as a standard block uses the available ratings of components and equipment. Ultimately, the overall design results in an optimized and reliable solution from all perspectives.

975-0747-01-01 Revision A 2–5


Wiring Box selection

Configuration of Conext CL Inverter’s wiring box depends on the installation location of the inverters, regulatory requirements like Arc Fault protection, and technical requirements related to reliability and safety like fuses and surge protection devices. In order to meet various requirements, Conext CL inverters offer five variants of the wiring box to connect DC and AC cables. This solution guide will help users to select the right type of wiring box.

Selection criteria

Under following situation or requirements, designer / client should choose either of the available options for Conext CL wiring box.

Base Model

• Design of PV system should have separate DC array combiner box with Fuses, SPD (optional) and DC switch before inverter input connections.

• Inverter will only accommodate one input for each MPPT, not multiple strings.

• On output side of Inverter, an AC box with SPD and AC switch/ MCB (optional) will be required.

• Inverter can be located on PV module structure with DC array box and AC box.

• Inverter can be located in group on PV field near first level AC combiner Box.

• If distance between Inverters and DC array combiners increases more than 10m, we recommend another set of SPD at inverter location before Inverter string inputs.

• Installer can use higher size of DC and AC cables to terminate in DC array box and AC Box. Inverter can be connected with highest regular size of cable it can accommodate with given terminal block size in Base model.

Essential and Essential+ Model

• Design of PV system doesn’t need DC array combiner box. All strings (up to 8) can be terminated directly on fuse terminals of Essential wiring box.

• A 40A DC switch is provided in wiring box. Installer can disconnect strings using this switch and there is no requirement of a separate DC switch box.

• Inverter will not have DC SPD inside the wiring box. If this model is chosen, we recommend an external installation of DC SPD.

• If termination to wiring box needs to be using MC4 connectors (not glands), Essential+ model has to be chosen.

• On output side of Inverter, an AC box with SPD and AC switch/ MCB (optional) will be required.


2–6 975-0747-01-01 Revision A



• If distance between Inverters and DC array combiners increases more than 10m, we recommend a set of SPD at both locations – At end of string and before Inverter DC input.

Optimum and Optimum+ Model

• A separate set of DC or AC SPD is not required with Optimum. So additional DC box will not be required.

• We recommend an AC MCB right after Inverter output to support AC SPD installed inside wiring box. Chosen MCB should have a well coordinated current rating with SPD and breaking capacity based on the peak impulse voltage rating of components installed.

• If termination to wiring box needs to be using MC4 connectors (not glands), Optimum+ model has to be chosen.



• If distance between Inverters and DC array combiners increases more than 10m, we recommend another set of SPD at inverter location before Inverter string inputs.

At any instance, we do not recommend installation of external components inside Conext CL inverter’s wiring box. This action would void warranty of Inverter.

975-0747-01-01 Revision A 2–7


Figure 2-2 Wiring box options (IEC only)

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2–8 975-0747-01-01 Revision A


Building Blocks of a Decentralized PV Power Plant

For a modular design approach, we recommend following solution bricks or building blocks to design a decentralize PV power plant using Conext CL inverters.

Table 2-1 Decentralized PV System Blocks

Brick Description Model Supplier

Inverters Conext CL 20kW or Conext CL 25kW

CL20000ECL25000E

Schneider Electric

DC Box – Optional (External, not Conext CL inverter’s wiring box)

DC disconnect switch

Thermal release

Surge Protection device

Fuses

Terminal Blocks

Enclosure

SW60DC & C120NADC for single MPPT

MX+OF

iPRD40

---

Linergy-NSYTRV

KaedraXT up to 100kW (4 inverters), Thalassa panels for more inputs

Schneider Electric

Schneider Electric

Schneider Electric

External

Schneider Electric

External

AC Box – Optional

AC circuit breaker

Surge protection device

Terminal blocks

Enclosure

iC60 series MCB

iPRD40 series

Linergy-NSYTRV

---

Schneider Electric

Schneider Electric

Schneider Electric

External

AC Combiner box

AC circuit breaker (MCB)

Terminal Blocks

Main Bus bar

AC Disconnect switch

Grounding terminal and bus

Surge protection device

Enclosure

iC60,iC120 and NG125 series

Linergy-NSYTRV

---

INS250 series switch

---

iPRD40 and 60

---

Schneider Electric

Schneider Electric

External

Schneider Electric

External

Schneider Electric

External

975-0747-01-01 Revision A 2–9


AC Re-combiner Box

AC circuit breaker (MCCB)

Terminal Blocks

Main Bus bar

AC Air circuit breaker or MCCB

Grounding terminal and bus

Surge protection device (optional)

Enclosure

NSX series MCCB

Linergy-NSYTRV

---

NT or NW series ACB or Compact NS type MCCB

---

iPRD

---

Schneider Electric

Schneider Electric

External

Schneider Electric

External

Schneider Electric

External

Transformer LV-MV Dyn11 Oil cooled / Dry type transformer

Minera series Schneider Electric

MV ring main system

MV RM6 or Flusarc type switchgear units

FluSARC, RM6 Schneider Electric

Grid Box Grid box with main MV circuit breakers CT-VT unit

Metering cabinet, Auxiliary transformer Communication equipment

Weather station

PV SCADA server

Utility Plant controller

FluSARC, RM6, SM6 type switchgear

SM6 type switchgear

---

Smart Box

---

Conext Control

M340 PLC

Schneider Electric

Schneider Electric

External

Schneider Electric

External

Schneider Electric

Schneider Electric

DC Solar PV cables

DC UV protected cables

--- External

AC cables AC LV and MV cables

--- External


2–10 975-0747-01-01 Revision A

Positioning Inverters


Inverter location

PV system design with Conext CL string inverters emphasizes the location of Inverter in the complete solution. The location of the inverter, in turn, drives selection of wiring box and system components.

We propose four types of standard design blocks in order to fit almost all types of installations. Each option has its advantage and disadvantage with respect to other installation but for every particular instance respective option serves the purpose in most efficient manner.

1. Inverters located on the PV field “electrically” grouped in AC Combiner box on the field – Inverters mounted on the PV panel structures and intermediate AC paralleling.

2. Inverters grouped on the PV field by clusters “electrically” grouped in AC combiner box on the field – Inverters mounted on dedicated structures connected to intermediate AC combiners.

3. Inverters spread on the field – Inverters mounted on PV panel structures and AC paralleling in MV stations.

4. DC distribution – Inverters close to LV/MV substation on a dedicated structure and AC paralleling in LV/MV substation.

Communication and Monitoring system

Data logger and portal

Energy meter

Router / switch

Enclosure

Power supply

Smart Box and Conext Insight portal

Schneider Electric

Grounding system

Bonding cable

Clamps and Connectors

--- External

DANGER





975-0747-01-01 Revision A 2–11


Option 1 (Inverters installed next to PV modules)

Inverters located on the PV field “electrically” grouped in AC Combiner box on the field – Inverters mounted on the PV panel structures and intermediate AC paralleling.

Advantages

• Less DC string cables

• Less DC I2R losses

• High Flexibility

• No need of dedicated structure for Inverter mounting

• Inverters close to PV modules reducing electrified portion of system during fault

• Covering most of the usable space within boundary

• Schneider iC60 type of breakers can be used in AC combiners – up to 5 inverters

Disadvantages

• This type of inverter placement requires external AC switch immediately after inverter

• Longer AC cables from Inverter to first level of AC combiners

• Higher AC cable losses

Selection criteria for Conext CL inverter wiring box variants for this option

• Base model + external DC box with DC fuses, DC SPD and DC switch

• Essential model + external DC SPD

• Optimum model

Figure 2-3 Standard Block Option 1 for a 1MW System

Conext CL

2–12 975-0747-01-01 Revision A


Option 2 (Inverters installed next to AC Combiner groups)

Inverters grouped on the field by clusters “electrically” grouped in AC combiner box on the field – Inverters mounted on dedicated structures connected to intermediate AC combiners

Advantages

• Less AC cables


• AC switch and AC SPD not required if considered in AC Combiner box

• Schneider iC60 type of breakers can be used in AC combiners – up to 5 inverters

Disadvantages

• Longer DC string cables might need to opt for higher size of DC cable

• Dedicated structures required for Inverter and AC combiner mounting

• Higher DC cable losses

• Use of RCD is probable




• Optimum model


Conext CL

975-0747-01-01 Revision A 2–13


Option 3 (Inverters installed next to PV inverters without first-level AC Combiners)

Inverters spread on the field – Inverters mounted on PV panel structures and AC paralleling in MV stations.

Advantages

• Less DC string cables

• Less DC I2R losses


• No need of dedicated structure for Inverter mounting

• Inverters close to PV modules reducing electrified portion of system during fault

• Covering most of the usable space within boundary

• First level AC combiners avoided resulting in cost savings

Disadvantages

• This type of inverter placement requires external AC switch immediately after inverter

• Very long AC cables from Inverter to AC combiners

• High AC cable losses

• High number of AC runs from Inverters to MV stations with increased time and chances of connection mistakes

• Increased size of AC cable will require higher size of terminal blocks in external AC combiner boxes

• Use of RCD is probable




• Optimum model


Conext CL

2–14 975-0747-01-01 Revision A


Option 4 (Inverters installed next to LV/MV transformer)

DC distribution – Inverters close to LV/MV substation on a dedicated structure and AC paralleling in LV/MV substation.

Advantages

• Less AC cables


• AC switch and AC SPD not required if considered in AC Combiner box

• Easy access to Inverters for service and maintenance

• RCD not required

Disadvantages

• Longer DC string cables might need to opt for higher size of DC cable

• External DC switch box with SPD required to protect long DC strings

• Combining DC strings might lose benefit of separate MPPT

• Dedicated structures required for Inverter and AC combiner mounting at MV station

• Higher DC cable losses

• Many long DC string cables increase possibility of wiring mistakes




• Optimum model


Conext CL

975-0747-01-01 Revision A 2–15


2–16 975-0747-01-01 Revision A

3 DC System Design

This chapter on DC Systems Design contains the following information:• String and Array Sizing Rules• String Connections to Conext CL

Inverter• DC System Component Design - The

DC Box

975-0747-01-01 Revision A 3–1

DC System Design

DC System Design

DC system design comprises of Module and Inverter technology assessment, string sizing, Arrangement and interconnection of strings, string cable sizing and length management, DC combiner box sizing if required, string / array cable sizing and routing up to Inverter’s terminal.

Out of the listed tasks, String sizing is the most important one as many other decisions depend on it. Like type and size of module mounting tables, interconnection arrangements and cable routing.

String and Array Sizing Rules

1. Number of modules x Voc (at t° min) < inverter Vmax

The no load voltage of the string (Voc x number of modules in series) at the minimum temperature of the installation location must be lower than the inverter’s maximum input voltage.=> This must be strictly observed. Otherwise the inverter may be destroyed.Apart from the aforementioned rule for preventing destruction of the invertertwo other limits must be observed.

2. Number of modules x Vmpp (at t° max) > inverter Vmin

The operating voltage (Vm x number of modules in series at all temperatures at the installation location) should fall within the inverter’s MPPT voltage range. Otherwise, the inverter will stall and energy supply will cease.

3. Isc strings < inverter Isc max

The total Isc current for strings in parallel must be lower than the maximum input current for the inverter. Otherwise, the inverter limits the supply of energy delivered to the network.We will analyze a use case to understand the string and array sizing in detail.

Number of PV Modules in the Series

For one CL inverter, the maximum number of PV Modules that can be connected in series will be provided under the most extreme conditions that might occur during the year. This configuration should consider the effects of temperature, maximum and minimum radiation in the following order, first, to ensure the

DANGER




3–2 975-0747-01-01 Revision A

DC System Design

inverter providing the minimum voltage start-up of the same, and secondly, to avoid failures in the inverter from surge, with the main objective of maximizing electricity production.

Minimum Number of PV Modules

We are basically calculating the minimum number of PV Modules in series. The worst case condition to consider is the maximum radiation incident on the plane of PV modules. Considering the voltage supplied by each solar cell decreases with the intensity of incident on the PV Module, the ideal would be that the number of PV Modules connected in series to provide at least the minimum voltage of inverter MPPT operation and that will be 350 V DC.

By defining:

Ns min = Number of PV Modules in series at least,

V min = Minimum voltage for maximum power point tracking,

V oc = Open circuit voltage of the panels,

V minr = Voltage at maximum power point

= Coefficient of variation of voltage with temperature,

Vmp = Voltage at thge point of maximum power

The losses depend on the temperature difference in cell temperature and 25 ºC of the Standard Test Conditions, the type of cell, encapsulated by the wind.

The Standard Test Conditions (STC) for measurement are the irradiation conditions and temperature of the solar cell, widely used to characterize the cells, PV Modules and solar generators and defined as follows:

• Irradiance : 1,000 W/m2

• Spectral distribution : Air Mass 1.5 G

• Cell temperature : 25 º C

To determine the temperature of the cell in any situation using the following formula:

Tc = T amb + (I inc (w/m2) × (NOCT–20)/800)

Where:

Tc = temperature of the cell, average temperature

Tamb = ambient temperature

I inc = incident radiation (max annual average)

NOCT = nominal operating cell temperature

For this use case, let's calculate the incident radiation when we have a Vmp of 1000 W/m2 and ambient temperature of 35 °C. Assume that NOCT of PV module correspond to 48 °C (standard value from manufacturer’s data sheet),

We have cell temperature as:

Tc = 35 + ((1000) × (48 – 20) / 800)) = 70 º C

975-0747-01-01 Revision A 3–3

DC System Design

The temperature difference of the cells relative to Standard Test Conditions will be:

70 – 25 = 45 º C with a 300 Wp Poly C-Si module

As the manufacturer indicates the variation with temperature of the open circuit voltage, Vmp to obtain the temperatures of cells shall be indicated by the power from the PV Module at this temperature divided by the intensity of maximum power at the same temperature.

This approximation is always the most correct, as the intensity is much more stable compared to the voltage and it will be possible to assimilate the intensity variation with temperature of the intensity of a short circuit with the maximum power.

With this data we can calculate the minimum number of PV Modules to be connected in series, taking into account that to maintain the minimum voltage tracking the maximum power is 350 V, we have: 300Wp Poly C-Si module,

Ns min = (Vmin / Vmin r) = (350 / 28.47) = 12.29 modules.

This is the minimum amount of PV Modules to be placed in series with each brand and ensure the functioning of the inverter 1000 W/m2 and 35°C ambient temperature.

Maximum Number of PV Modules

The maximum number of PV modules is calculated at the minimum ambient temperature, considered at the particular geographical installation.

In the second extreme case, the maximum number of PV panels in series that can be installed to connect the inverter, is given by the ratio between the maximum input voltage of the inverter and the open circuit voltage of PV Modules in a situation where the inverter starts with an ambient temperature of 0º C.

Conext CL inverter starts at 130W nominal power value and consider that approximately we can get to 40 W/m2 radiation accident.

Conservatively considering Tamb min. = -5 ºC.

Operating as in the previous case, we have a cell temperature:

Tc = -5 + ((40 × (48 – 20)/800)) = -3.6 ºC,

The temperature difference of the cells relative to Standard Test Conditions will be:

-3.6 – 25 = - 28.6 ºC

PV Module Vmpp/T Vmp Vmp (70ºC)

300Wp Poly C-Si PV module

-0.445%/ º C 35.60 28.47

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Since the maximum voltage is 1,000 V borne by inverters we can know the maximum number of panels to be placed in series will be: for a 300Wp Poly C-Si module,

Ns max = (Vmax inv / Voc (0ºC amb)

= (1000 / 49.27) = 20.29

With this we get the maximum number of PV Modules to be placed in series.

Any chosen configuration between 13 to 20 modules will fit, but 20 would be the most desirable choice.

Number of PV Modules in Parallel

The maximum number of strings installed in parallel connected to Conext CLConext CL inverters, will be calculated taking into account the worst case for intensity in the field panels to the inverter.

Whereas the PV Module temperature in 70 °C would have:

2 MPPT / inverter with a maximum input current of 31A DC per MPPT

For 3 strings per MPPT, the maximum current would be:

Impp = 8.30 x 3 = 24.9 Amp at 25 °C Amp modules and 1,000 W radiation.

If the PV Modules reach 70º C, the increased current would be:

9.16 A × (0.087 / 100) × (70 - 25) × 3 (strings) = 1.07 Amp

Current Total: 24.9 + 1.075 = 25.975 Amp is below the 31 Amp.

The configuration chosen will have 3 strings per MPPT as maximum.

Here we complete our task of string and array sizing.

Schneider Electric offers Conext Designer – A PV string sizing tool to accurately calculate the size of strings for the selected modules with Conext CL inverters.

The tool is easy to use and available for both Mac and Windows users. The following link can be used to download the tool.

http://solar.schneider-electric.com/product/conext-designer/

String Connections to Conext CL Inverter

Conext CL inverter’s maximum DC Input current is 31A and Max. Short circuit current is 40A for independent MPPT operation.

Any string to be connected to each MPPT input has to be within this limit of Short circuit current for Independent MPPT operation.

PV Module Voc/T Voc Voc (-3.6 ºC)

300Wp Poly C-Si PV module

-0.332%/ º C 45.0 49.7

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For a Single MPPT operation (MPPT inputs shorted) current limits to follow are 62A for Impp and 77A for Isc.

For the sizing of Strings to connect with Conext CL inverters, one must observe the short circuit current of PV Module it is going to connect with and number of parallel string being connected to each MPPT or overall. If there is any multiplier to be considered based on local standardization or safety authorities, cables and overcurrent protection devices should be rated for this multiplier (like 25% overrated).

The DC switch provided with Conext CL inverter is rated 40A DC current and it breaks both MPPT inputs simultaneously when operated.

Schneider Electric recommends to use One MPPT configuration in case of odd number of strings being connected to Inverter, if there is no significant difference within strings (like shadowing or different tilt or a different configuration). In case of difference in configuration of strings (like tile, shadow, mismatch etc.) dual MPPT operation is advisable with balanced input.

20kW Conext CL Inverter if connected to four strings, can be used without fuses but just using Y type string connectors (near PV modules) to combine two strings into one and terminating one cable on each MPPT terminal. This solution is most economical option for string connections. Similar approach is not possible for 25kW CL Inverters as more than two strings in parallel requires fuses to avoid reverse currents in case of fault in one of the parallel connected strings.

DC String Arrangement and Cable Sizing

String cables are sized for three parameters mainly voltage drop, ampacity and short circuit current. Generally for the PV applications in IEC practice, 4 mm2 Cu, double insulated, UV protected flexible cables are used to carry string current which is in order of 8 to 10 Amp.

All DC string cables should be designed for not more than 1% voltage drop.

Following general formula can be used to calculate the % voltage drop in DC string cables.

Where:

Vd, voltage drop (volts)Vop, the operating voltage at Standard Test ConditionsK, the metal temp coefficient for copper at 25 °CL, the one way conductor length (m)I, the operating current at Standard Test Conditions

Cm, the conductor area (circular mm2)Pct_Vd, the voltage drop at nominal operating conditions (%)

Vd2 K L I

Cm------------------------------- =

Pct_VdVd

Vop----------- 100=

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When a Conext CL inverter is selected with Basic wiring box model, user should carefully define the DC side protection and disconnect requirement depending upon the location of inverter with respect to PV module strings.

Length of cable from PV modules to the Inverter / DC Combiner box depends on the String interconnections and cable routing at the back of PV modules.

There are several ways modules can be installed using some standard racking options. We suggest our customers to analyze following parameter before deciding the type of arrangement to interconnect.

Example:

If 300Wp modules to be connected to a 25kW Conext Inverter for any assumed location where string sizing ends up in 18 modules/ string and considering 20% oversizing we have following system to connect.

1. DC size – 25kw X 1.2 = 30kWp

2. AC size – 25kW

3. Module size – 300Wp Multi C-Si

4. String size – 18 module/string

5. Number of Strings – (30X1000)/(300X18) = 5.556

Since this set up does not end up in a complete number, we have following choices:

• Connect 5 string to each inverter with oversizing of 8%

• Connect 6 strings to each inverter with oversizing of 29.6%

• Reduce the rating of Modules from 300Wp to 280Wp and connect 6 strings with 20% oversizing

• Increase the rating of Modules form 300Wp to 330Wp and connect 5 strings with 19% oversizing

• Reduce the number of modules in string to 16 and connect 6 strings with 15% O/S

• Increase the number of modules in string to 20 and connect 5 strings with 20% O/S

Recommended basic rules for string formation

1. Select EVEN number for modules in a string.

2. Select EVEN number of strings in a inverter, if possible.

3. Try to maximize modules per string within Voc and Vmpp limits of Inverter.

4. Formation of strings should be designed in a way that cable management at the back of modules could be followed as per electrical installation rules and with shortest string cable length as well as minimum bends.

5. Support the Connectors and avoid sharp bend from PV Module cable box.

6. If possible, keep the PV module strings connected and formed in horizontal lines to avoid row shadow impact on all strings in each wing of racks or trackers.

7. Follow the instructions of PV module manufacture to select Portrait or Landscape position of Modules.

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8. Connect shadowed strings to same MPPT and others to the different MPPT to achieve maximum harvest.

9. Do not combine separate ratings of PV modules in one string

Now considering above basic rules and given situation, we decide to connect 20 PV modules of 300Wp in one string and 5 strings to each inverter.

String cable lengths should be managed by deciding proper interconnection method and racking block design. An example for 5 string connection with landscape modules is as below.

The other way to connect the string when portrait arrangement is chosen can be:

Figure 3-1 String arrangement and interconnection example with Landscape

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It is essential to understand and select the right circuit components when any PV system is designed. After the cables, racking and strings, we will move on to the next circuit component identified as DC Box.

DC Box consists of Disconnect switches, Surge protection devices and Thermal release (optional) for emergency operation.

Schneider Electric offers DC Box solution for such installation.

DC System Component Design - The DC Box

Function

1. SW60DC switch – Disconnects each MPPT input of the inverter from the DC line disconnect.

2. PRD-DC – Protects the inverter against voltage surges coming from DC lines (Applicable for the Base model only and if circuit required additional SPD).

3. MX+OF releases / MN releases Controls the release of the switches remotely for emergency purpose – For Rapid shutdown purpose of for fireman safety requirement.

Typical use

1. The DC box is an optional offer, but is necessary when:

• Local regulations require the use of external DC switch disconnects

• Local regulations require the disconnection of DC lines remotely (generally as close as possible to the PV modules) in case of emergency

• The lightning risk assessment concludes that protection by SPD is required

• However, DC Box is required when the base model is chosen

2. The PV array of each MPPT input is preferably disconnected separately

• One switch disconnect per DC input

3. DC box is installed close the PV modules when:

Figure 3-2 String arrangement and interconnection example with Portrait oriented modules

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• Protection by SPD is required and the distance between PV modules and the inverter is higher than 10 m

• Emergency control of the DC lines is required and the inverter is located far from the PV modules or inside the building

• Wiring between DC box and inverter must use 6mm² cross-section PV conductors

Advantages of the offer

1. Two models of DC box:

• with surge protection

• without surge protection

2. Each model is suitable for both CL 20000 E and CL 25000 E inverters.

3. One DC box per inverter, for both MPPT inputs. This allows for separate disconnection of the PV arrays.

4. Easiness of the DC connections by using PV connectors mounted on the DC box or close to the DC box.

5. Range for CL 20000 E and CL 25000 E

6. Two models – DC01(R), DC02(R)

• DC01 with switch-disconnects only – DC01R includes release for emergency control

• DC02 with switch-disconnects and surge voltage protection – DC02R includes release for emergency control

7. Schneider Component References

Figure 3-3 DC Box Schematic Diagram

Table 3-1 DC Box Component Reference

Components Model Reference Number

Switch Disconnect

SW60 DC – 1000DC, For combined MPPT use C20NADC

A9N61699 and A9N61701

Optional Release MX+OF48-130 VDC12-24 VDC

26947A9N26948

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DC System Design


iPRD40r -1000DC A9L16436

Enclosure Thalassa PLS modular 24 NSYPLS2727DLS24

Note: For combined MPPT operation, C120NADC type DC MCB should be used instead of SW60DC.

Table 3-1 DC Box Component Reference


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12

4 AC System Design

This chapter on AC Systems Design contains the following information:• AC System Design• AC Component Design

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AC System Design

AC system of PV plant consist of AC switch box, AC combiner box, AC Re-combiner box, AC Cables, Trenches, LV-MV Transformer, Ring main units at MV stations in PV field, MV cable circuit and MV station at Grid Box.

AC low voltage circuits with high amount of power needs extreme care to achieve reliability, safety and highest level of availability of system. Selection of circuit breakers (MCB and MCCBs), Disconnect switches, Protection devices and Cables is the key to achieve all three objectives.

Safety and availability of energy are the designer’s prime requirements.

Coordination of protection devices ensures these needs are met at optimized cost.

Implementation of these protection devices must allow for:

• the statutory aspects, particularly relating to safety of people

• Technical and economic requirements

The chosen switchgear must:

• withstand and eliminate faults at optimized cost with respect to the necessary performance

• limit the effect of a fault to the smallest part possible of the installation in order to ensure continuity of supply

Achievement of these objectives requires coordination of protection device performance, necessary for:

• managing safety and increasing durability of the installation by limiting stresses

• managing availability by eliminating the fault by means of the circuit-breaker immediately upstream.

The circuit-breaker coordination means are:

• Cascading

• Discrimination

If the insulation fault is specifically dealt with by earth leakage protection devices, discrimination of the residual current devices (RCDs) must also be guaranteed.

DANGER




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Circuit Breaker Coordination

The term coordination concerns the behavior of two devices placed in series in electrical power distribution in the presence of a short circuit.

Cascading or backup protection

This consists of installing an upstream circuit-breaker D1 to help a downstream circuit breaker D2 to break short-circuit currents greater than its ultimate breaking capacity lcuD2. This value is marked lcuD2+D1.

Standard IEC 60947-2 recognizes cascading between two circuit-breakers. For critical points, where tripping curves overlap, cascading must be verified by tests.

Discrimination

This consists of providing coordination between the operating characteristics of circuit breakers placed in series so that should a downstream fault occur, only the circuit breaker placed immediately upstream of the fault will trip.

Standard IEC 60947-2 defines a current value ls known as the discrimination limit such that: if the fault current is less than this value ls, only the downstream circuit-breaker D2 trips if the fault current is greater than this value ls, both circuit-breakers D1 and D2 trip. Just as for cascading, discrimination must be verified by tests for critical points.

Discrimination and cascading can only be guaranteed by the manufacturer who will record his tests in tables.

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Note: Discrimination and cascading can only be guaranteed by the manufacturer who will record his tests in tables.

Installation standard IEC 60364 governs electrical installations of buildings. National standards, based on this IEC standard, recommend good coordination between the protection switchgear. They acknowledge the principles of cascading and discrimination of circuit-breakers based on product standard IEC 60947-2.

For more details on Limitation, Cascading and Discrimination of circuit breakers Schneider Electric’s Low voltage Expert Guide No.5 – “Coordination of LV protection devices” should be referred.

AC Component DesignRight after Conext CL inverter AC terminals, an AC switch box should be installed depending on the distance from the first AC combiner. This AC switch box may or may not have an AC surge protective device. If the wiring box for inverter is Optimum or Optimum+, C switch box can be selected without AC surge protection device.

Figure 4-1 Summarizing Table

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AC Component Design

The AC Switch Box

Function

1. iC60H, 40A MCB protects and disconnects inverter from the AC line.

2. Quick PRD protects the inverter against voltage surges coming from AC lines.

Typical use

1. The AC box is an optional offer, but is necessary when:

• the distance or an obstacle between inverter and AC combiner box prevents the safe disconnection of the inverters at the AC combiner box level and/or

• the distance between inverter and AC combiner box is more than 10 m and may prevent the safe surge voltage protection of the inverter at the AC combiner box level

2. AC box is located near the inverter

• generally needs an outdoor enclosure

3. Possible long distance between AC switch box and AC combiner box

• requires cross-section terminals for output cabling higher than 6 mm2 (maximum cross-section of the cables at the AC plug)

Advantages of the offer

1. Two models of the AC box:

• with surge protection

• without surge protection

Possibility to increase cross-section cables to reduce AC losses - output cables terminals up to 35 mm2

2. Range for CL 20000 E and CL 25000 E

3. Two models – AC01, AC02

• AC01 with switch-disconnect only

• AC02 with switch-disconnect and surge voltage protection

Figure 4-2 AC Switch Box Schematic Diagram

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AC Cable sizing

AC Cable sizing calculation consists of ampacity, voltage drop, short circuit calculation and thermal de-rating of AC cables.

To limit the power loss up to acceptable limits, after selecting a suitable size of cable with proper ampacity, short circuit rating and voltage grade the most important part is to calculate voltage drop. We advise to keep AC cable overall power losses in range of <1%. This would ensure smooth operation of multiple units in parallel at one transformer LV winding.

Formulae commonly used to calculate voltage drop in a given circuit per kilometer of length.

Where:

X, inductive reactance of a conductor in /km

, phase angle between voltage and current in the circuit consideredIs, the full load current in amps

L, length of cable (km)

R, resistance of the cable conductor in /kmUn, phase to phase voltageVn, phase to neutral voltage

AC cable sizes between Conext CL inverters and AC Combiner boxes will mostly depend on the distance between them. Output current of Conext CL 20kW inverter is 32A and 25kW Inverter is 37A (33A for NA version) Considering the de-rating factors due to cable laying methodology and thermal de-rating due to conduits, mostly 16 mm2 4 core AL cable fits in to the most instances.

The following table provides recommended maximum cable lengths for 8.86 mm2, 13.29 mm2 and 21.14 mm2 conductor size from inverter to AC distribution box. It indicates tentative figures for power loss with respect to length and size. We advise the installer to carry out a detailed cable sizing calculation specifically for each inverter and location.

Table 4-1 AC Box Component Reference


AC MCB iC60H 40A or 50A, 4p A9F87440, A9F87450


I Quick PRD40r -1000DC A9L16294

Enclosure Thalassa PLS modular 12 for AC01

Thalassa PLS modular 24 for AC02

NSYPLS1827PLS12

NSYPLS2227DLS24

U 3Is R cos X sin+ L=

%Vd 100UUn

-----------------=

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AC Component Design

It is essential to calculate and consider the correct fault level on each combiner bus level in order to select the right size of cable, MCB, MCCB and RCD, Surge protection and Disconnect devices.

Following methodology can help to understand this calculation.

If the AC cable length exceeds 10 m (32.8ft), the use of an AC switch box closer to the inverter is recommended. This switchbox can be used to connect higher size of cable, if required to avoid voltage drop.

Aluminum cables can be used to connect Conext CL Inverter output to AC Combiner Box. Designer/installer has to be careful about calculating the cable voltage drop and power loss while designing the system especially using Aluminum cables. It is very important to consider both resistive and reactive component of voltage drop in cable sizing calculation. Reactive part of Impedance of cable plays essential role in parallel operation of Inverters. Target should be to reduce it as much as possible to increase the number of parallel connected inverters at LV winding of Transformer (considering intermediate AC distribution boxes).

AC Combiner Box

AC combiner box is first level combiners, mostly located in the PV field in large utility scale projects. AC combiner box houses the first level protection for Inverters on AC side (if not applied in AC box). The outgoing line from AC combiner to LV/MV station holds disconnects or if required, it should be protected with circuit breakers.

Table 4-2 Percentage losses for Cu cable w.r.t maximum AC cable length

AC Cable length 10 mm2 16 mm2 25 mm2

20 KVA - % losses for copper cable

25m 0.4% 0.22% 0.14%

50m 0.7% 0.45% 0.28%

75m 1.1% 0.67% 0.42%

100m 1.4% 0.90% 0.56%

25 KVA - % losses for copper cable

25m 0.7% 0.42% 0.27%

50m 1.3% 0.85% 0.53%

75m 2.0% 1.27% 0.80%

100m 2.7% 1.69% 1.06%

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Function

1. Combines AC currents coming from several inverters.

2. Isolates the combiner box from AC line.

3. Output switch-disconnector, INS type.

4. Protects AC lines to inverters against over-currents.

5. Circuit breaker C60 N/H/L (according prospective current), four poles, C curve, 40 A (for CL 20kW) & 63A (for CL 25kW).

6. Protects inverters against voltage surges from AC line.

7. Quick PRD, 4p.

8. If not done at the AC box level.

Typical use

1. AC combiner box is located near the inverters.

2. Long distance between AC combiner box and AC distribution box.

3. Requires high cross-section terminals for output cabling.

Depending upon the number of inverters being combined at AC combiner’s bus-bar, the incoming lines can be protected using MCBs or MCCBs. Selection of this component depends upon rated circuit current, expected fault current, fault clearing time and remote operation requirements. Length of cable connected between Ac combiner output and AC Re-Combiner input plays very important role as longer length reduces the fault current to break. See the following example circuit.

Figure 4-3 AC Switch Box Schematic Diagram

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Above circuit has 20m length from AC combiner to AC Re-combiner. Resulting Fault level at AC Combiner bus bar is 17.64kA and choice of Breaker is NG125N MCCB (25kA).

Now, increase the length of cable and check again!

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This time the Fault current reduces to 10.84kA allowing to select C120H MCB with 15kA fault level.

Following graph indicates the relation between Iscmax and length of LV array cable.

Please note that size and type of cable selected here affects the fault level on bus-bar of AC combiner box. So length as well as size of cable should be considered carefully to select the economical yet most effective and safe circuit breaker solution.

Methodology to calculate the Fault level at AC Combiner Bus-bar

For a combiner box connected to Re-combiner box with 120mm2 size AL cable of 20m length and Re-combiner box connects to a 1000kVA 22kV/400V, 6% transformer.

Fault level at AC combiner bus bar = Voltage × Voltage correction factor C/ Fault impedance

= 400×1.05 / (ZTR-LV + ZCable)×sqrt3

= 400×1.05 / {(RTR-LV + Rcable)2+(XTR-LV

2 + Xcable2)1/2}×sqrt3

For a 1000KVA, 22kV / 400V transformer with Voltage factor c=1.05 and Short circuit impedance 6% and Load loss of 10550kW,

Transformer LV impedance ZTR-LV

= 400×400×0.06/1000×1000

= 0.0096 Ohms

RTR-LV = Losses×LV voltage/ (kVA capacity)2

= 10550×400/10002×10002

= 0.001688 Ohms

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AC Component Design

XTR-LV = sqrt(Z2-R2) = 0.009450432 Ohms

Cable Impedance Zcable = Sqrt (Rcable2 + Xcable

2)

Rcable = Resistance @ 90oC× length / runs×1000)2 = 0.0064515

Xcable = Reactance×length/1000 = 0.00164342

Fault level at AC combiner bus bar

= Voltage × Voltage correction factor C/ Fault impedance

= 400 × 1.05/ (ZTR-LV+ZCable)×sqrt3

= 400 × 1.05 / {(RTR-LV+ Rcable)2+(XTR-LV

2+Xcable2)1/2}×sqrt3

= 400 × 1.05 / {0.0081122 + 0.011097822} ½ × sqrt3

= 17.64 kA

So for this scenario Following will be the choice of circuit breakers with calculated fault current.

Selection of Switch-disconnect for AC Combiner box also depends on this fault current and nominal continuous current the AC Combiner box is going to handle.

Like for an AC Combiner box combining 5 Conext CL inverters (5×25kW = 125kW) operating current can be as high as 181 A (125×1000/400V× sqrt3). Considering the operating margin 200A switch-disconnect to withstand up to 20kA fault current would be a right choice for above case. Compact INS type switch Disconnects can be used for this purpose.

AC Re-Combiner Box

• The AC Re-Combiner box is adapted according to the type of grid box and the requirements of the utility.

• The AC Re-Combiner box is divided into two parts:

• LV AC Re-Combiner to connects to all AC combiner boxes while protecting the cabling and possibly measuring currents

• LV connection to connect to the grid box while ensuring compatibility with grid box and utility requirements

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AC Re-combiner box re-combines all AC Combiner box at one bus-bar and accumulated power flows to the transformer LV winding to get transferred to MV network.

AC Re-combiner box is or mostly will be located at LV-MV station inside the kiosk or outside on concrete pad. All incoming lines from AC Combiners in PV field are connected to incoming line’s molded case type circuit breakers and outgoing to LV transformer winding can be connected to either a MCCB or an Air circuit breaker depending on the space requirements.

Selection of these MCCBs and ACB should be following the similar rule we encountered for AC Combiners. It is worth to notice once more that discrimination and cascading of circuit breakers helps to design more accurate protection philosophy as well as can save lot of capital cost because of the reduced fault level capacity of components due to limitation feature.

Fault level at transformer’s LV terminal will be mostly same as fault level on AC Re-combiner’s bus-bar due to very short distance between Transformer and Re-combiner panel.

Methodology to calculate Fault level on AC Re-combiner’s bus bar

Fault level at AC Re-combiner bus bar

= Voltage × Voltage correction factor C/ Fault impedance

= 400×1.05/(ZTR-LV+Zgrid)×sqrt3

= 400×1.05/{(RTR-LV+ RLV-grid)2+(XTR-LV

2+XLV-grid2)1/2}×sqrt3

Considering the MV connection at 22kV and Grid short circuit power of 500MVA, we will use following values to calculate Grid impedance at LV side of transformer.

MV voltage: 22kV, Short circuit power from grid: 500MVA, Transformer LV voltage: 400V, Voltage factor c for MV grid: 1.1, Size of transformer: 1000KVA

First, calculate MV impedance,

ZMV-grid = (RMV-grid2+XMV-grid

2)1/2

ZMV-grid = c × Grid voltage/Grid current

= 1.1× 22000/ (500X106 / 22000×sqrt3)

= 1.0648 Ohms

XMV-grid = 0.995 × ZMV-grid = 0.995 × 1.0648

= 1.059476 Ohms

RMV-grid = (ZMV-grid2-XMV-grid

2)1/2 = 0.106347 Ohms

Then, calculate Grid LV impedance from Grid MV values,

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XLV-grid = XMV-grid × (LV Voltage 2 / MV Voltage 2)

= 1.059476 (4002/220002)

= 0.00035 Ohms

RLV-grid = RMV-grid × (LV Voltage 2 / MV Voltage 2)

= 0.106347 (4002/220002) = 3.52×10-5 Ohms

Then, calculate Transformer impedance values and Transformer LV impedance

ZTR-LV = 400×400×0.06/1000×1000

= 0.0096 Ohms

RTR-LV = Losses×LV voltage/ (kVA capacity)2

= 10550×400/10002×10002

= 0.001688 Ohms

XTR-LV = sqrt(Z2 - R2)

= 0.009450432 Ohms

Using the above four values in formulae for Bus-bar fault level calculation,

Fault level at AC Re-combiner bus-bar

= 400×1.05/{(RTR-LV+ RLV-grid)2+(XTR-LV

2+XLV-grid2)1/2}×sqrt3

= 25.26 kA

Selection of incoming circuit breaker, bus-bar and outgoing circuit breaker shall be based on this fault level calculation and nominal rated current.

For a 1 MVA standard block, with 40 Conext CL inverters, 8 AC Combiner boxes combining 5 inverters each, the AC Re-combiner box will have 8 incomers, each with 200A nominal current and respective fault level. Length of cables between AC Re-combiner and transformer (being very short) doesn’t make much difference to selection of circuit breaker’s fault level. Transformer impedance and grid short-circuit fault level makes a small difference but not significant. The major difference comes from size of transformer and LV voltage level. Designer should consider this during designing the system.

Following example gives some idea about selection of breaker.

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AC System Design

When we replace 2500kVA transformer with 1000kVA transformer, fault level significantly reduces on AC Re-combiner’s bus-bar and NSX630F and N type breakers become eligible to be used for incomers.

Above example is just for understanding of dependency of circuit breaker selection on bus-bar fault level. And dependency of bus-bar fault level in selection of components.

Distribution control

Distribution control may be required for monitoring purposes.

• Can capture measurements from NSX µLogic devices or capture utility metering information.

• Can be located inside the AC Re-Combiner box if room is available or in a dedicated enclosure close to the AC Re-Combiner box.

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AC Component Design

Function

1. Combines AC currents coming from the AC combiner boxes.

2. Connects to the grid box while ensuring compatibility with the grid box and compliance with grid connection requirements.

3. Protects the AC lines connected to the AC combiner boxes

• using C120 circuit breakers or Compact NSX according current and Fault level at bus bar, optionally with Vigi modules.

4. Protects against voltage surges coming from AC lines

• using type 1 or type 2 SPD, protected by circuit breaker.

5. Isolates the AC Re-Combiner box (and the whole PV installation) from the AC line.

6. Optionally, monitors currents and energies at each input.

• Use of µLogic™ 5.2E module for protection and monitoring purposes.

7. When a remote emergency shutdown is required, an optional release MN or MX is used at the LV connection stage.

Typical use

1. Different types of AC Re-Combiner box are required according to the type of grid box and to the need for an external protective relay.

2. In the case of connecting only one AC combiner box, only the LV connection stage of the AC Re-Combiner box is required.

3. The AC Re-Combiner box can be located indoors or outdoors, normally close to the grid box.

4. Buildings protected with lightning rods require the use of type 1 SPDs at AC Re-Combiner box level.

Figure 4-4 Distribution Control Diagram

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AC System Design

Recommended System Design

We recommend following configuration for reliability and higher system availability.

System Technical Summary

Block size: 1000 kVA

Transformer: 1000kVA, 5.5%, 22000V/400V, Dyn11, Oil immersed type

AC Re-combiner: 8 incoming, 1 outgoing, SPDIncoming – NSX type MCCB 200A, curve C, 3POutgoing – Compact NS or NT type Air CB 1600A with TM-D or Micrologic trip unit, 3PSurge protection on Main bus-bar – iPRD 65rBus bar – Cu, 400V, 30kA (mostly with 500MVA grid capacity)Grounding bus, Metal enclosure (IP 54 or higher)

AC Combiner*: 5 incoming, 1 outgoing, SPDIncoming – iC60- N (upto 10kA) or H (upto 15kA) type MCB 40A, curve C, 4POutgoing – Interpact INS250-200A type Switch-Disconnect, 4PSurge protection on Main bus-bar – iPRD 40rBus bar – Cu, 400V, 15kA (if Cable to Re-combiner is <95mm2 for >30m)Grounding bus, Metal enclosure (IP 54 or higher)

AC Cables:AC Combiner to Re-combiner 4C, 1.1kV grade, AL, XLPE, 95mm2 or higherInverter to AC Combiner – 4C, 1.1kV grade, AL, XLPE, 16mm2 or higher

DC Cables:Module strings to Inverter 4 or 6 mm2, solar PV grade 1000V, UV protected

Note: *If four incoming AC Combiners are selected, Kaedra XT type enclosure can be used for a cost competitive solution. NSX160 MCB can be used to further reduce the cost.

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AC Component Design

CB Protection – Discrimination tables for selection.

To achieve right level of discrimination and cascading between selected circuit breakers, follow these tables. If the installed circuit breakers have different combinations, follow “Complementary technical information” : Low voltage catalogue – document to check more discrimination tables.

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AC System Design

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AC Component Design

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4–
20

5 Important Aspects of a Decentralized System Design

This chapter on the aspects of a decentralized system design contains the following information:• Selection of Surge Protection device

for Decentralize PV systems• Grounding System Design for

Decentralized PV systems• Grid Connection • Role of Circuit Impedance in Parallel

Operation of Multiple Conext CL String Inverters

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Important Aspects of a Decentralized System Design

Selection of Surge Protection device for Decentralize PV systems

Surge arrestors protect the electrical wiring, components and system from lightning surges. Role of surge arrester is to drive the lightning current to the earth in very short time (<350 microseconds). However surge arrestors are not intended to be exposed to a permanent over voltages. In that case, it might create a short circuit and may damage the switch board. iPRD PV-DC direct current surge arresters are designed to protect against Over voltages due to a lightning strike: of the "DC" input to the inverter and of Photovoltaic panels.

Surge protection selection points:

• The protection level of SPD must be lower than the impulse withstand voltage level of equipment protected by SPD

• For a TNC grounding scheme, 3P SPDs should be used

• For a TNS grounding scheme, 3P+N SPDs should be used.

• If the PV system is installed in vicinity (within 50m) of a lightning protection rod or lightning termination, Type 1 SPD will be required to safeguard the inverter from lightning discharge currents as It is used to conduct the direct lightning current, propagating from the earth conductor to the network conductors.

• Geographical conditions cause the specific level of Lightning Flash density. Based on the level of lightning flash density and commercial value of equipment protected, level of surge protection has to be decided and so is the fault level (kA) of SPD.

• After having chosen the surge protection device for the installation, the appropriate disconnection circuit-breaker is to be chosen from the opposite table. Its breaking capacity must be compatible with the installation’s breaking capacity and each live conductor must be protected. E.g. 3P+N SPD must be combined with a 4P MCCB or MCB.

Use of SPDs on DC circuits

iPRD PV-DC type surge protection devices should be installed in a switchboard inside the building. If the switchboard is located outside, it must be weatherproof. Withdrawable iPRD PV-DC surge arresters allow damaged cartridges to be replaced quickly.

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The surge arrester base can be turned over to allow the phase/neutral/earth cables to enter through either the top or the bottom. They offer remote reporting of the “cartridge must be changed” message.

Depending on the distance between the “generator” part and the “conversion” part, it may be necessary to install two surge arresters or more, to ensure protection of each of the two parts.

Calculation for DC surge protection:

• to protect the inverter you need to have Protection level Up (surge arrester) < 0,8 Uw (inverter)

• if the distance between the module and inverter > 10m, a second surge protection should be installed close to the module except if Up < 0,5 Uw (module)

Uw is the impulse withstand.

The CL should be category III and that means its Uw = 6kV.

The 1000V modules are usually cat A so their Uw = 8kV.

iPRD40r 1000V DC surge arrestor is Up = 3.9kV.

So, 3.9 < 0.8 x 6 = 4.8kV: the protection of the inverter is good.

And, 3.9 < 0.5 x8 = 4kV: there is no need of additional surge arrestor to protect the modules.

The following diagram indicates the additional SPD requirement considering that impulse withstand voltage of PV module is lesser than Up of SPD inside Conext CL inverter.

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Following is a use case example to understand the installation of SPDs.

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In the case of PV architecture without an earthed polarity on the DC side and with a PV inverter or with galvanic isolation, it is necessary to:

• protect each string of photovoltaic modules with a C60PV-DC installed in the junction box near the PV modules;

• Add an insulation monitoring device on the DC side of the PV inverter in order to indicate first earth fault and actuate stoppage of inverter as soon as it occurs.

Restarting will be possible only after eliminating the fault.

Schneider Electric has certified coordination between the surge arrester and its disconnection circuit breaker (IEC 61643-11 2005 version). The following diagram indicates the possible coordination with Type 2 SPDs.

For the installations with lightning rod within 50m of area, Type 1 SPDs to be used with following coordination with disconnecting devices.

Figure 5-1 Installation of SPDs

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Use of SPD on AC Circuits in Decentralized PV systems

AC output circuit of Conext CL inverter can be protected by selecting Optimum model of Conext CL inverter with AC SPD inside the wiring box of the inverter. Client must note that the following points have been chosen using the Optimum type wiring box with AC SPD.

• This AC SPD is provides type 2 protection to Inverter from AC system surges from grid. For the protection of AC Low voltage system, we recommend to select respective type of SPD based on country code and area lightning protection requirements.

• We recommend using suitable circuit disconnecting means with SPD device inside or outside the inverter wiring box.

• The SPD provided inside wiring box is not meant to protect AC LV grid components.

Figure 5-2 Type 2 SPDs

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• For an effective surge protection, shorten the length of cables. Lightning is a phenomenon that generates high frequency voltage. 1 m length of cable crossed by a lightning current generates approximate over voltage in order of 1000V.

• In practice, consider intermediate grounding terminals inside the switch boards to shorten the cable lengths. IEC 60364-5-534 mandates to restrict the overall length of cables (connected to SPD and terminating to ground) up to 50cm

Here is the circuit of internal SPD connections of Conext CL wiring box.

In 3phase AC LV systems, surge protection is also dependent upon the type of grounding system is followed for the wiring of 3 phases and neutral. Following examples provide understanding about connection of SPDs in AC LV circuits.

Figure 5-3 Circuit of Internal SPD Connections

Figure 5-4 TN-S Earthing System, 3-Phase + Neutral

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Grounding System Design for Decentralized PV systems

General Understanding of Grounding

The different grounding schemes (often referred to as the type of power system or system grounding arrangements) described characterize the method of grounding the installation downstream of the secondary winding of a MV/LV transformer and the means used for grounding the exposed conductive-parts of the LV installation supplied from it.

The choice of these methods governs the measures necessary for protection against indirect-contact hazards.

The grounding system qualifies three originally independent choices made by the designer of an electrical distribution system or installation:

The type of connection of the electrical system (that is generally of the neutral conductor) and of the exposed parts to earth electrode (s)

A separate protective conductor or protective conductor and neutral conductor being a single conductor

The use of earth fault protection of overcurrent protective switchgear which clear only relatively high fault currents or the use of additional relays able to detect and clear small insulation fault currents to earth

Figure 5-5 TN-C Earthing System, 3-Phase

Figure 5-6 MEN Earthing System, 3-Phase

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In practice, these choices have been grouped and standardized as explained below.

Each of these choices provides standardized grounding systems with three advantages and drawbacks:

• Connection of the exposed conductive parts of the equipment and of the neutral conductor to the PE conductor results in equi-potentiality and lower over voltages but increases earth fault currents.

• A separate protective conductor is costly even if it has a small cross-sectional area but it is much more unlikely to be polluted by voltage drops and harmonics, etc. than a neutral conductor is. Leakage currents are also avoided in extraneous conductive parts.

• Installation of residual current protective relays or insulation monitoring devices are much more sensitive and permit in many circumstances to clear faults before heavy damage occurs (motors, fires, electrocution). The protection offered is in addition independent with respect to changes in an existing installation.

Grounding for PV Systems

PV systems are either insulated from the earth or one pole is earthed through an overcurrent protection. In both set-ups, therefore, there can be a ground fault in which current leaks to the ground. If this fault is not cleared, it may spread to the healthy pole and give rise to a hazardous situation where fire could break out. Even though double insulation makes such an eventuality unlikely, it deserves full attention.

For the two following reasons the double fault situation shall be absolutely avoided: Insulation monitoring devices or overcurrent protection in earthed system shall detect first fault and staff shall look after the first fault and clear it with no delay:

Figure 5-7 Reverse Current

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• The fault level could be low (e.g. two insulation faults or a low short-circuit capability of the generator in weak sunlight) and below the tripping value of overcurrent protection (circuit breaker or fuses). However, a DC arc fault does not spend itself, even when the current is low. It could be a serious hazard, particularly for PV modules on buildings.

• Circuit breakers and switches used in PV systems are designed to break the rated current or fault current with all poles at open-circuit maximum voltage (UOC MAX). To break the current when UOC MAX is equal to 1000V, for instance, four poles in series (two poles in series for each polarity) are required. In double ground fault situations, the circuit breaker or switches must break the current at full voltage with only two poles in series. Such switchgear is not designed for that purpose and could sustain irremediable damage if used to break the current in a double ground fault situation.

The ideal solution is to prevent double ground faults arising. Insulation monitoring devices or overcurrent protection in grounded systems detects the first fault. However, although the insulation fault monitoring system usually stops the inverter, the fault is still present. Staff must locate and clear it without delay. In large generators with sub arrays protected by circuit breakers, it is highly advisable to disconnect each array when that first fault has been detected but not cleared within the next few hours.

Example of grounding circuit connections for a decentralized PV design.

Sizing of grounding conductor should be followed by country and area installation codes for grounding PV systems. Selection of system components like SPDs, MCCB and MCB, Disconnect switches, Panel enclosures and cables should be in accordance with the type of grounding system followed by utility and installed type of transformer. Typical practices followed by local area safety council and fire-fighting departments should be taken into consideration while designing the PV system grounding scheme.

Figure 5-8 Grounding Circuit Connections

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Transformer selection for decentralize PV plants with Conext CL

Transformers for PV application are designed with respect to the size of AC block. We recommend multiplication of 1000kVA block for large MW scale plants. For smaller residential or commercial plants which needs to connect to Utility POC at medium voltage level can be ranged anywhere between 100kW to 1000kW.

Some features a transformer for PV system could be,

• A shield winding is recommended as a dU/dt filter between the low voltage and high voltage windings.

• LV-MV impedance Z (%) for the transformer must be within 4.5% to 6%; nominally 6%. In case of multiple LV windings, Z (%) refers to a simultaneous short circuit on all LV terminals.

The configuration of the MV transformer should take into account the local grid frequency and should meet local and regional standards.

The low voltage (inverter-side) windings of the MV transformer can only be configured as floating Wye (Dyn11). If the MV side of the system is grounded Wye, use of a floating Wye on the inverter side may not be allowed by the local utility. Make sure you understand your system configuration and the utility’s rules before installation.

The following standard sizes of transformers are listed under IEC and the table indicates generalized power loss values for transformer ratings and impedance.

Table 5-1 Power loss values for transformer ratings and impedancea

a.According to EU regulation 548/2014 – Ecodesign

On load losses No load lossesUcc Sn Dk Ck Bk Ak E0 D0 C0 B0 A0

4% 50 kVA 1350 W 1100 W 870 W 750 W 190 W 145 W 125 W 110 W 90 W

100 kVA 2150 W 1750 W 1475 W 1250 W 320 W 260 W 210 W 180 W 145 W

160 kVA 3100 W 2350 W 2000 W 1700 W 460 W 375 W 300 W 260 W 210 W

250 kVA 4200 W 3250 W 2750 W 2350 W 650 W 530 W 425 W 360 W 300 W

315 kVA 5000 W 3900 W 3250 W 2800 W 770 W 630 W 520 W 440 W 360 W

400 kVA 6000 W 4600 W 3850 W 3250 W 930 W 750 W 610 W 520 W 430 W

500 kVA 7200 W 5500 W 4600 W 3900 W 1100 W 880 W 720 W 610 W 510 W

630 (4%)

8400 W 6500 W 5400 W 4600 W 1300 W 1030 W 860 W 730 W 600 W

6% 630 (6%)

8700 W 6750 W 5600 W 4800 W 1200 W 940 W 800 W 680 W 560 W

800 kVA 10500 W 8400 W 7000 W 6000 W 1400 W 1150 W 930 W 800 W 650 W

1000 kVA

13000 W 10500 W 9000 W 7600 W 1700 W 1400 W 1100 W 940 W 770 W

1250 kVA

16000 W 13500 W 11000 W 9500 W 2100 W 1750 W 1350 W 1150 W 950 W

1600 kVA

20000 W 17000 W 14000 W 12000 W 2600 W 2200 W 1700 W 1450 W 1200 W

2000 kVA

26000 W 21000 W 18000 W 15000 W 3100 W 2700 W 2100 W 1800 W 1450 W

2500 kVA

32000 W 26500 W 22000 W 18500 W 3500 W 3200 W 2500 W 2150 W 1750 W

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For multi MW PV systems, we recommend to parallel 40 Conext CL inverters to each LV winding of transformer. This defines the size of block to 1000kVA for 25kW and 800kVA for 20kW inverters. Its advisable to use lower impedance and oversized transformer for smooth parallel operation of Inverters. Like for a 500kW system (20 x 25kW CL inverters) a 630kW transformer with 4% impedance would be the best choice. Its recommended to use the standards size of transformer available in market to avoid long manufacturing time and higher market prices.

Schneider Electric offers Minera PV type high efficiency oil immersed transformer for photovoltaic systems up to 1250kVA and 36kV, 50/60 Hz.

Monitoring System Design

Since the profitability of photovoltaic installations depends mainly on operational uptime, it is essential to ensure that they are permanently up and running. The best way of ensuring this is to install a monitoring and control system covering key equipment of the installation. It is also essential to select the right monitoring and control offer that supports the control requirements, if any, of the utility.

Monitoring System Design: Commercial Rooftops and Small Ground Mounted Farms

Each Conext CL Inverter has a data logging capacity and an in-built web server that helps you to monitor performance and perform diagnostics of the single inverter locally at the site. Additionally, Schneider Electric will launch several other offers for remote monitoring and control of Conext CL enabled decentralized PV plants.

Basic remote monitoring

Remote monitoring and basic open loop control

Typical plant size

<= 200kW 100kW to multi-MW

Hardware offer

No additional hardware required. InsightLink feature of Conext CL.

Conext SmartBox-BA

An outdoor rated enclosure with:

• Data-logger

• Power supply

Conext SmartBox-ES

An outdoor rated enclosure with:

• Data-logger

• Power supply

• Revenue grade energy meter

• Extended I/Os

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Conext SmartBox Conext SmartBox is designed to be a true plant operator assistant for configuration, monitoring and diagnostics.

Key features of Conext SmartBox are:

1. SmartInstall

• installation wizard for speedy set-up

2. SmartConfig

• ability to configure all the inverters in the plant with minimum manual data entry

• file import option to easily replicate standard configurations

Hardware features

Simple plant monitoring with no additional hardware installation

• Outdoor rated

• Easy to install data logger to monitor upto 64 devices (inverters/ meters/ sensors) over modbus/485

• Accept external control signals over modbus/TCP

• Scalable to support larger plants through master-slave configuration

Same strengths as SmartBox-BA with add-on features like:

• A pre-wired revenue grade energy meter

• An ability to accept grid control commands using digital/analogue signals

• An ability to monitor field equipment status (e.g. fire alarms) using digital inputs

• Optional optical fiber switch to lay high speed optical fiber network for larger plants

Remote monitoring platform

Conext Insight

Basic remote monitoring

Remote monitoring and basic open loop control

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3. SmartDiagnose

• on demand 10 seconds data logging for accurate fault diagnostics

• various energy and events log export options for deeper data analysis

4. Other key features

• plant and inverter performance analysis with up to five years of data

• configurable e-mail alerts on device faults

Conext Insight Conext Insight is the remote monitoring and asset management platform to help you maximize ROI of your PV investments.

Key features of Conext Insight are:

1. Key metrics for all stakeholders

• performance ratio, output as % of installed capacity, remuneration, environmental impact

• quick and insightful plant portfolio level performance reporting

2. Top-to-bottom analysis granularity to minimize truck rolls in response to service calls

• multi-plant, single plant, plant sections and individual inverter level analysis

• real time access to events logs for accurate remote fault diagnostics

3. Analytics reporting to synthesize vast amount of data

• visual analytics optimized for decentralized PV architecture to help in quick troubleshooting

• inverter level performance deviation alarms

• analysis of top generators of errors and ticket resolution efficiency

• plant level performance notifications e.g. performance ratio decline

4. Richness of data access options

• 24x7 remote access through user friendly HMI optimized for PCs and tablets

• e-mail notification of plant performance issues

• easy e-mail set-up for periodic performance reports e.g. multi-plant performance comparison report, yield report etc.

• quick download of energy and events log in CSV/jpg/pdf format

Remote monitoring for small plants (8 inverters)

• Connect each Conext CL inverter directly to Conext Insight portal via router

• No additional monitoring hardware investment is required

• Easy and simple solution for small plants

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Remote monitoring for small to large rooftop and plant (64 inverters) – Smart-Box BA

• Inverters and accessories (e.g. sensors/meters etc.) are daisy chained to Conext SmartBox using RS-485

• Conext SmartBox connects to Conext Insight via router

Remote monitoring and control of 5MW ground mounted solar farm (200 inverters of 25kW each) – SmartBox ES

• Plant is divided into four blocks of 1.25MW (50 inverters each)

• Total five Conext SmartBox-ES in master-slave configuration connected using optical fiber network:

Figure 5-9 Remote monitoring of a 100kW plant (4X25kW Conext CL inverters) using InsightLink feature of inverters

Figure 5-10 Remote monitoring of a 625kW rooftop plant (25X25kW Conext CL inverters) using Conext SmartBox-BA and Conext Insight portal

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• 4 x Conext SmartBox-ES in slave mode (one for each 1.25MW block). Slave SmartBoxes collect data from the connected inverters/sensors and send it to Master SmartBox

• 1 x Conext SmartBox-ES in master mode (at the plant level). Master SmartBox collects data from Slave SmartBoxes and connected sensors and sends it to portal. Master SmartBox also accepts control commands from utility and sends the control commands to each Slave SmartBox in the network

3rd-party monitoring solutions such as Meteocontrol™, Solar-Log™, Enerwise™, and Deck™ are pre-tested and qualified for plug and play.

For more information visit:

Meteocontrol: www.meteocontrol.com Solar-Log: www.solar-log.com Enerwise: www.enerwise.asiaDeck: www.deckmonitoring.com

Figure 5-11 Remote monitoring and control of a 5MW ground mounted plant (200X25kW Conext CL inverters) using Conext SmartBox - ES in master-slave mode and Conext Insight portal

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Grid Connection

Grid Connection

Connecting to a Public LV network

Rules for connecting a PV installation to an LV network

1. In regards to connecting to a public LV network, power limits vary by country.

For example, 250 kVA in France, 100 kVA in Spain and Italy, 30 to 100 kVA in Germany.

2. Some local grid codes allow the connection of a PV installation to the grid without use of an additional protective relay when:

• Inverters are VDE 0126 certified: in France up to 250 kVA, in Germany up to 30 kVA

3. When a protective relay is required, it must be installed in the distribution box or in the distribution control box.

• Functions and adjustments of the protection relay vary by country (Min-Max U, Min-Max F)

Grid Box

1. The connection to an LV network is made through a grid box provided by the utility.

• Interface is at the terminals of the metering unit or at those of the main circuit breaker.

• Grid box can be located indoors or outdoors.

2. The grid box is divided into two parts:

• Service connection area accessible only by the utility for service needs (metering, disconnecting)

• User connection area accessible by the customer for safety needs (isolation, protection…)

3. User connection area is generally equipped with a main circuit breaker.

• The main circuit breaker can be provided by the customer. If the main circuit breaker is not included in the grid box, it must be integrated in the distribution box.

4. Three types of grid boxes (GB1, GB2, GB3) are available to account for varying types of grid connections.

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LV connection interfaces

Connection of PV plant to utility grid terminates at point of common coupling (PCC). Schneider Electric also provides medium voltage Grid Box solution for achieving utility requirements at PCC. Generally Grid box mostly consist of:

• A MV switchgear of rated grid voltage, current and fault current breaking capacity.

• Tariff metering for Utility and Check Metering for PV plant owner.

• PV plant controller

• Supervisory, Control and Data Acquisition system for PV plant (if required by either utility or client)

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Role of Circuit Impedance in Parallel Operation of Multiple Conext CL String Inverters

• PV plant service transformer

• AC power distribution box

• Communication center for SCADA systems and PV plant security (optional)

• Main weather station of PV plant

Depending upon the equipment and systems, size of Grid box changes and sometime can be multiplied and divided.

Along with basic monitoring capability, Schneider offers very advance state of art PV plant SCADA systems with Conext control monitoring platform as requested by client.

Contact Schneider Electric for further understanding of configuration of SCADA systems, PV plant communication and Grid controller offers.

Role of Circuit Impedance in Parallel Operation of Multiple Conext CL String Inverters

Multiple string inverters are paralleled in decentralized PV power plants. These inverters are connected to MV grid using three phase transformer. Transformer leakage impedance, Cable impedance and Grid impedance constrained the number of inverters can be paralleled. Interaction between the AC network grid and distributed PV Inverters (DG – Distributed Generators) may generate instabilities due to the overall system low frequencies resonance and it is recommended to avoid high impedance grids (weak grids).

Figure below illustrates a general single line diagram, AC grid-connected Conext CL string inverters (DG(1)...DG(n)) through two transformer stages. The PV power plants are usually galvanically separated from the transmission system (table I) by the following two transformation stages:

• Low-to-medium voltage transformer (Tx.LV-MV)

• Medium-to-high voltage transformer (Tx.MV-HV)

The PV power plant system stability is influenced by the total equivalent impedance defined as follows with the recommendable limits:

• ZcLV - LV interconnection line impedance <1% p.u.

• ZTxLV.MV - LV to MV transformer impedance <6% p.u.

• ZTxMV.HV - MV to HV transformer impedance <9% p.u.

• ZcHV - HV interconnection line impedance <1% p.u.

Ztotal = ZcLV + ZTxLV.MV + ZcMV.HV + ZTxMV.HV + ZcHV

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For smooth, reliable and continuous parallel operation of Conext CL string inverters, it is very important to follow following recommendations from Schneider Electric.

• Restrict the AC cable impedance up to 1% of power loss.

• Restrict the Transformer impedance (between LV and HV winding) up to 4.5% (630 kVA) and up to 6% (<1250 kVA). We do not recommend AC block size of more than 1000kVA for Conext CL 25kW inverters and 800kVA for Conext CL 20kW Inverters. Please contact us if the system size is higher than 1000kVA and we will assist you to configure the system.

• If a three winding transformer is used (HV-LV-LV) including above point, also maintain the short circuit impedance of minimum or greater than 9% between each LV winding.

• Oversize (by 20%) the transformer kVA capacity with respect to installed inverter kW capacity.

• AC cable sizing calculation should also consider the reactive impedance of cables and not just resistive.

• Grid impedance is a very important parameter for this consideration. Calculate the grid impedance at PCC before designing the overall PV plant circuit.

Figure 5-12 Generic AC Grid Connected Inverters Diagram

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6 Layout Optimization

This chapter on layout optimization contains the following information:• Layout Design Rules• Layouts

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Layout Optimization

Layout Design Rules

As a recommendation, the following layouts can be used to design standard blocks using Conext CL inverters.

• Selection of structural design should be based on the string length and number of strings connected to each inverters.

• Arrangement of Modules on PV structure should be decide in line with length of string to reduce DC PV string cable route length.

• In case of single axis trackers, this requirement becomes more stringent from both inverters and tracker’s perspective.

• Location of inverter should be decided prior to define the block size.

• Connection of strings to Inverter and use of DC array combiner will be dependent on location of string inverter.

• Location of AC array combiner box and LV-MV station should be slected in line with block size, to divide blocks and reduce cable length from AC combiners to LV-MV station.

• In most cases, standard defined block should be multiplied to avoid several wiring mistakes and shorten installation time.

Layouts1. 250kW Layout with zigzag string connections

2. 250kW Layout with straight string connections

• Distributed Inverters

• Grouped Inverters

3. 500kW Layout with all three types of inverter location configurations

4. 1000kW Layout with grouped Inverters

5. 1000kW Layout with distributed inverters

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6–4 975-0747-01-01 Revision A

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6–6 975-0747-01-01 Revision A

Layouts

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975-0747-01-01 Revision A 6–7

6–
8

7 Frequently Asked Questions (FAQ)

This chapter of FAQs contains answers to general questions that may arise when considering Conext CL Inverters in designing a power system.

975-0747-01-01 Revision A 7–1

Frequently Asked Questions (FAQ)

Safety Information

Frequently Asked Questions1. Can we interchange the wiring box of CL Inverter (Base to Optimum to

Essential)?

No. The wiring box supplied with the Conext CL inverter has to be used with its matching inverter body. In case the need arises, consult Schneider Electric to discuss for solution.

2. Can we install third party components inside the wiring box?

No. Components installed inside the wiring box are tested in factory before dispatch and hold warranty for the product. If any external component is installed inside the wiring box, that may void warranty.

3. What type of Transformer can be connected with CL Inverters?

Dyn11 or Dyn1 type transformer should be connected with Conext CL inverter. LV voltage of transformer should match the inverter’s AC output voltage and MV voltage should match the grid connection voltage.

4. Can we install the wiring box of the CL Inverter at other location and the inverter body someplace else?

No. The wiring box and the inverter body have to be installed at the same location as displayed in the installation manual.

5. What is the solution if my AC cable size is higher than the terminal size of Conext CL inverter?

An external AC terminal box has to be used in certain situations. This box will have input from the inverter with the maximum cable size the inverter terminal can fit (25mm2). And, the output terminal of this AC box can have higher sized cables as required by design.

6. Do I need assistance from Schneider Electric for first installation of Conext CL inverters?

No. For first installation, follow Schneider Electric’s installation manual for the Conext CL inverter. Get yourself familiarized with possible hazardous situations, follow recommended installation practices, and use a certified installer. In case of any difficulty, you can contact Schneider Electric for assistance.

DANGER




7–2 975-0747-01-01 Revision A

Frequently Asked Questions

7. Do I need to contact Schneider Electric at the time of designing PV system configuration for proposal?

We recommend that Installers / Developers contact Schneider Electric when they start considering the use of Conext CL inverters. This way we can help you to design the most reliable and cost competitive solution with no technical surprises during installation.

8. How can I update firmware version of Conext CL inverter?

Conext CL inverter firmware is available at http://solar.schneider-electric.com/product/conext-cl/. You can download the latest firmware and upload it using a thumb drive or your laptop. Every time the Conext CL inverter is being installed, the installer should use the latest firmware version available on the website.

9. Where can I find Conext CL OND file for PVsyst simulation?

You can find it at http://solar.schneider-electric.com/product/conext-cl/

10. Is there any tool from Schneider Electric to help my sizing the strings for my installation?

Yes. Schneider Electric has developed a design tool named Conext Designer to size the strings for users of Schneider inverters. This tool is not for predicting energy generation but it helps users for string sizing only. You can find this tool on this link. http://solar.schneider-electric.com/product/conext-designer/Download your copy and install it for further use.

11. Is measurement of power inside the Conext CL inverter good enough for tariff metering?

Measurement of power inside the Conext CL inverter takes place with 0.5 class accuracy. Generally tariff metering has stringent requirements for accuracy and other compliance related to utility. User has to discuss this requirement in detail with the utility company.

12. Where can I find an Installation manual for Conext CL inverters?

Installation manual for Conext CL inverter can be found at http://solar.schneider-electric.com/product/conext-cl/

13. What is the Schneider Electric customer care contact detail for technical support?

Customer care contact details in your respective region are found athttp://solar.schneider-electric.com/tech-support/

14. Does Schneider Electric provide Engineering, Procurement, Installation and Commissioning services for PV systems?

Yes. Contact us for more details and discussion for our services.

15. Which other system components Schneider Electric can offer?

Follow the chart provided under topic “Building blocks of Decentralize PV system” in this document to check the offers form Schneider Electric.

16. What is the maximum oversizing I can achieve for Conext CL inverters?

We recommend 20% oversizing. It can be more depending upon the climatic conditions. If there is more than 30% oversizing required, please contact us for our advice. In any case, the limits of short circuit current for the inverter should not be violated.

975-0747-01-01 Revision A 7–3

http://solar.schneider-electric.com/product/conext-designer/

http://solar.schneider-electric.com/product/conext-cl/

http://solar.schneider-electric.com/tech-support/






17. Which configuration will be preferred when? – to use both MPPTs or short the MPPTs.

Schneider Electric recommends to use One MPPT configuration in case of odd number of strings being connected to the inverter, if there is no significant difference within strings (like shadowing or different tilt or a different configuration). In case of difference in configuration of strings (like tile, shadow, mismatch etc.) dual MPPT operation is advisable with balanced input. Conext CL inverters are capable to handle 60-40 ratio of imbalance in string power.

18. What if I connect unbalanced string combination (3 and 2 on each MPPT) with Conext CL inverter?

Conext CL inverter is capable to connect 60-40% imbalance condition. So user can connect 3-2 or 4-3 configuration. But be careful about not violating the short circuit rating of the inverter DC input.

19. How a choice of transformer gets affected by the inverter’s operating capability?

The inverter’s operational capability depends on Transformer in two aspects.Parallel operation of inverter: Inverter’s parallel operation is function of short circuit impedance (Z%) and transformer is a circuit component with very large impedance portion of overall circuit. We recommend keeping the Impedance of transformer as low as possible.Conext CL inverter supports TNS,TNC, TN-C-S and TT wiring schemes. It does not support IT scheme. When Transformer is selected, it is important to match Utility side winging requirement as per Point of connection and Low voltage side winding requirement as per the inverter’s operational compatibility.

20. What is the limit of power factor Conext CL inverters are capable of?

Conext CL can operate within 0.8 lead and 0.8 lag power factor limit.

21. Does Conext CL inverter support LVRT requirement?

Yes. It does. LVRT requirement is specified in respective PV grid code of country. Conext CL inverter firmware is programmed to follow the LVRT requirement (curve) during certification of each country. Contact us to know the list of countries Conext CL inverters are certified for.

22. Do I need to have power factory model of my PV plant if I use Conext CL inverter? Can Schneider Electric provide it?

This requirement is generally requested by Utilities to include the model of your power plant into their power system. We recommend that clients should discuss this type of requirements with utility well ahead during the system planning stage and choose the right wiring scheme and metering scheme. A billable power factory model can be created based on client’s request. If you have such a requirement, please contact us for further discussion.

23. What type of support I can have form Schneider Electric for designing configuration of my PV system?

Schneider Electric provides ready reference documentation for designing the system, for example, the solutions guide, installation manual, training material, etc. If you need any additional information or services, contact us for more discussion.

24. Which parameters I do have to confirm and use to order Conext CL inverters?

7–4 975-0747-01-01 Revision A


Unlike centralizes inverters, Conext CL string inverters are simple to configure and install. Since it is simple, there isn’t any technical information sheet to fill in order to buy these inverters. Schneider Electric’s sales representatives would help customer to buy the right type of inverter and associated wiring box. This solutions guide can be used to select the right wiring box.

25. When the temperature de-rating does begin for Conext CL inverter? How much it de-rates?

26. What if I install the Conext CL inverter in outdoor place?

Conext CL inverter is rated for outdoor duty. It can be installed as per instructions provide in Installation Manual. Please follow installation manual for further information of outdoor installation.

27. What is the normal manufacturing time after confirmation of order for Conext CL inverters?

Table 7-1 De-rating for 500 Vdc and 800V, 230 Vac 25 Kw

Condition Output Powerin kilo watts

Output Powerin kilo watts

0 25.033 25

10 25.033 25

20 25.033 25

30 25.033 25

40 25.033 25

46 25.033 25

50 22.859 25

55 19.28 22.009

60 15.6 20.3

Table 7-2 De-rating for 350 Vdcand 800V, 230 Vac 20 Kw

Outside Ambient in °C 350V 800V

20 20.08 20.08

30 20.08 20.08

40 20.08 20.08

44 20.08 20.08

50 19.97 20.08

54 17.24 18.04

60 13.54 14.84

975-0747-01-01 Revision A 7–5


Generally it takes 10 to 14 weeks to manufacture CL inverter in Schneider Electric’s Indian manufacturing g location in Bangalore. We recommend clients to consider this time with the shipping time to plan their project. If there is a steeper timeline, please contact us for further discussion.

28. Where can I find the test certificates for Conext CL inverter?

CL inverter certifications are available athttp://solar.schneider-electric.com/product/conext-cl-na-solar-inverter/

29. What type of warranty Schneider Electric offers for Conext CL inverters?

Warranty terms for Conext CL depends on the region of installation. Users can find the information about warranty athttp://solar.schneider-electric.com/product/conext-cl-na-solar-inverter/

30. Do I need to oversize the transformer when I connect to multiple Conext CL inverters?

We recommend equal or oversized transformer for Conext CL inverters. Especially when there is large number of CL inverters connected in parallel to one transformer low voltage winding, we recommend to oversize the transformer by 20%.

31. What type of wiring schemes Conext CL inverter can be connected with?

Conext CL inverter can be connected with TN-S, TN-C, TN-C-S and TT wiring schemes. IT wiring scheme is not supported.

32. How can I choose right type of wiring box for my installation?

Our sales representatives will help clients to select the right wiring box based on the electrical single line diagram of project. This solutions guide provides necessary information and details to select the wiring box. If client needs to discuss this with Schneider Electric, please contact us.

33. How many Conext CL inverters with wiring boxes can be delivered in 40ft containers?

45 Inverters + Wiring boxes can be supplied in a 40 feet standard shipping container.

34. How much space I need to install Conext CL inverters side by side?

600mm (23.6 in) on right and left sides, 915mm (36 in) at bottom and 200mm (7.8 in) at top.

35. If any component inside Conext CL inverter gets damaged during installation how can I buy a new component?

Contact your Schneider sales representative to buy the components.

36. What type of monitoring system I can use with Conext CL inverters?

Schneider Conext CL inverters support third party monitoring solutions. Refer the monitoring section of this solutions guide for further details.

37. Is it mandatory to use AC circuit breaker at the output of Conext CL wiring box?

We recommend that installer / client uses the circuit breaker to support AC surge protection device.

38. What is the brief specification of DC switch disconnect provided in wiring box of Conext CL inverters?

Model: X100.40D4-G X0342 Make: Santon

7–6 975-0747-01-01 Revision A

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Details of DC Switch disconnect provided in Conext-CL inverter can be found at this link. http://www.santonswitchgear.com/download/loose-switches.html

39. What is the brief specification of DC and AC Surge protection devices provided in wiring box of Conext CL inverters?

Conext CL wiring boxes are equipped with Type 2 surge protection devices. Specification of Schneider SPD can be found at this link.DC SPD: 16436 - PRD-DC 40r 1000PV modular surge arrester - 2 poles - 1000V with remote transfer

AC SPD: A9L16564 - modular surge arrester iPRD40r - 3 poles + N -

340 V - with remote transferhttp://www.schneider-electric.com/products/ww/en/1600-din-rail-modular-devices/1615-acti-9-surge-protection-devices-spds/61707-ipf-iprd/

40. What is the brief specification of DC Fuses provided in Conext CL wiring box?

Conext CL inverters are equipped with touch safe Fuse holders. But the inverter will be supplied without fuses and empty Fuse holders. This is due to the fact that client would need to select the right size of fuse (10A or 15A) depending upon the type of PV module being used, size and number of strings and any factor of oversizing required from local installation standards. Due to this, there are probably several possibilities of fuses and we recommend that client should size the fuse correctly for safe and reliable operation.

41. Is there an Anti-Islanding protection provided in Conext CL inverter?

Yes. Conext CL inverter is equipped with anti-islanding protection.

42. What is output operating voltage range capability/limits, response to network voltage sags?

The inverter will deliver full power at unity power factor with +10% and -3% grid voltage variation.

43. What is the wake up value and power watt for Conext CL inverters?

Wakeup voltage - 150 VHysteresis values: Fall power: 200V (Vbst min)Start power - 950V (Vdc Max), The minimum start up power is 100 watts (Under normal Grid voltage, and PV voltage).If the Grid voltage and PV voltage (250 <= PV < = 950) values are out of range, then the minimum start up power would be 250 watts.

Parameter CL 20000 E CL 25000 E

Vbst.min 250 V 250 V

Vmppt.min 350 V 430 V

Vmppt.max 850 V 850 V

Vdc.max 970 V 970 V

Vdc.uv 200 V 200 V

975-0747-01-01 Revision A 7–7

http://www.santonswitchgear.com/download/loose-switches.html

http://www.schneider-electric.com/products/ww/en/1600-din-rail-modular-devices/1615-acti-9-surge-protection-devices-spds/61707-ipf-iprd/


44. Can we control the output of the inverter is 1% steps, what is the time resolution?

1% steps is possible and time latency is 5 sec (max), typically 1 sec

45. How many inverters can be firmware upgraded at one time via Ethernet start connection, one or multiple? Does it have to be in Intranet or Internet?

One , either of the network

46. How long does it take for Ethernet firmware upgrading for single inverter?

10 to 15 mins (approximately)

47. How can we ensure the wiring box top ports are protected from water and dirt ingress until the inverters are mounted?

Can you please confirm that there are no other complications in the mounting of these units separately, which will be installed upon the table frameworks?Wiring box is IP65 with good protection from water and dirt. There is one Connector cover which will protect all the connectors on the top of wiring box. Make sure this cover will need to be remained till inverter mounting on the top of the wiring box. Please find the details on question Number 26 on page 7–5.

7–8 975-0747-01-01 Revision A

Schneider Electric


As standards, specifications, and designs change from time to time, please ask for confirmation of the information given in this publication.

© 2015 Schneider Electric. All rights reserved.

975-0747-01-01 Revision A Printed in

http://solar.schneider-electric.com

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