nrs 097-series / grid code discussion - sasgi 097-series / grid code discussion: gerhard botha ......

NRS 097-series / Grid Code Discussion:

Gerhard BothaResearch, Testing and Development

2014/04/16

SASGI Meeting:

2014/05/06 2

Overview

• Introduction

• What is NRS 097?

• What do we have?

• What do we want?

• Comparison of international documents

• Proposed amendments

• Conclusions

2014/05/06 3

Introduction

• Requests from residential (municipal) customers to install PV

• Key drivers:

• personal, local, regional or national objectives to increase the renewable energy component of electricity utilized;

• a whole range of drivers including sustainability, climate change, future fossil price volatility risk aversion, utility energy shortages, etc.;

• changing dynamics of electricity generation costs, with embedded generation close to the source of consumption becoming economically or financially viable; and

• in particular contexts where embedded generation may help alleviate localized network capacity constraints or improve power reliability to key circuits on the customer premises (particularly if it can be dispatched or coupled with energy storage).

2014/05/06 4

Introduction

• Why do we (utilities) require standards?

• Key drivers:

• Safety

• Safety

• Safety

2014/05/06 5

Introduction

• Key drivers:

• LV networks designed for power flow downstream;

• Incorrect interfacing can affect network performance and quality of supply;

• Overvoltages, voltage dips and spikes, interruptions, harmonics, etc;

• Safety:

• Equipment incorrectly rated – both utility and customer;

• Equipment damaged due to SSEG not meeting requirements;

• Utility network energised… Maintenance personnel;

• Customer network energised…

• Reclosing operations;

• Emergency personnel, e.g. fire brigade.

What is NRS 097-1?

• Does not exist yet

• Planned to be based on Eskom “Standard for Interconnection of Embedded Generators”

• Complements the SA Grid Code (RPP, NC)

• Protection details

• Anti-islanding details

• SCADA details

• Metering details

• Applicable to units connected to MV and higher voltages

2014/05/06 6

What is NRS 097-1?

3 REQUIREMENTS

3.1 General Requirements

3.2 Legal And Regulatory Requirements

3.3 Operational Safety

3.4 Generator Capabilities And Operation

3.5 Requirements For The Utility Network Interface

3.6 Requirements At The PUC And PGC

3.7 Metering

2014/05/06 7

What is NRS 097-1?

4 SUPERVISORY CONTROL AND DATA ACQUISITION

4.1 Gateway Equipment

4.2 Protocols For Information Exchange

4.3 Telecommunication Interface Requirements

4.4 Minimum Data Exchange Requirements

5 TESTS

5.1 Pre-commissioning And Commissioning Tests

5.2 Maintenance Tests

2014/05/06 8

What is NRS 097-2?

• Set of industry standards that define technical requirements:

• the utility interface,

• generator requirements and

• utility implementation guidelines

• for the interconnection of small scale embedded generators to LV distribution networks of a utility.

• The standards cover:

• Utility interface requirements (NRS 097-2-1 - published, being reviewed)

• Embedded generator requirements (NRS 097-2-2 - draft)

• Utility framework (NRS 097-2-3 – being published)

• Procedures for implementation and application (NRS 097-2-4)2014/05/06 9

What is NRS 097-2?

• Reviewed international documents:

• EA ER G83/1-1: Recommendation for the connection of SSEG (<16 A per phase) in parallel with the public LV networks.

• IEC 60364-7-712, Electrical installations of buildings – Requirements for special installations or locations – Solar PV power supply systems.

• IEC 61727, PV systems – Characteristics of the utility interface.

• IEC 62116, Test procedure of islanding prevention measures for utility-interconnected photovoltaic inverters.

• NRS 048-2, Electricity supply – Quality of supply – Part 2: Voltage characteristics, compatibility levels, limits and assessment methods.

• SANS 10142-1, The wiring of premises – Part 1: LV installations.

• SANS 60947-2/IEC 60947-2, Low-voltage switchgear and controlgear –Part 2: Circuit-breakers.

2014/05/06 10

What is NRS 097-2?

• WG requirements/decisions:

• Generic document (i.e. generation source/device independent)

• < 1’000kVA (vs. 100kVA)

• > 4.6kVA must be balanced units

• > 13.8kVA must be three-phase units (vs. 10kVA)

• Safety requirements (including redundancy)

• Anti-islanding, disconnection for abnormal network conditions

• Metering (examples)

• NOTE: not for tariffs, but technical requirements

2014/05/06 11

What do we have?

• NRS 097-2-1: Published December 2010

• Standard Conditions for Small Scale (less than 100kW) Embedded Generation within Municipal Boundaries;

• 22 September 2011;

• Municipalities need to keep proper records and report to NERSA, what, where, how much etc.;

• Comply with requirements from NRS 097-2-1;

• Update proposed to NERSA by AMEU/ESKOM;

• Grid code

• Renewable Power Plants – version 2.6 published Nov 2012;

2014/05/06 12

What do we want?

• NRS 097-2-2 (Type Testing) draft:

• Review international standards again – International exposure

• No single document that will fulfil the requirements for SSEG connection and type testing for LV networks in South Africa

• Specific comparison for utility interface:

• VDE 4105

• EN 50438

• IEC 61727, 61000-series, other

• ER G83/1-1 and G59/2

• IEEE 1547 / UL 1741

• Align with international best practices!2014/05/06 13

Document Comparisons

• NRS 097-2-X: <100kW, LV only, 50Hz – connection requirements

• IEEE 1547: <10MVA, Typically MV, 60Hz – type testing IEEE 1547.1

• ER G83/1-1: <3.66kW per phase per installation (3ph : 11kW), LV only, 50Hz – connection requirements and type testing

• ER G59/2 applies to everything else.

• VDE 4105: <100kVA on LV network, 4.6kVA per phase per installation (3ph : 13.8kVA), LV only, 50Hz – connection requirements and type testing

• UL1741: relaxed requirements in some instances for <30kW – detailed testing

2014/05/06 14

Document Comparisons

• IEC 61727: <10kVA, PV only – connection requirements

• IEC 62116: No size indications – specific mention of 61727, PV only –anti-islanding testing

• IEC 60364-7-712: No size indications, building installations, PV only –wiring standard

• IEC 62446: No size indications, seems to be aimed more at house installations, PV only – documentation, commissioning tests and inspection requirements – wiring verification

2014/05/06 15

Comparisons (Basic Requirements)

2014/05/06 16

Description NRS097-2-1:2010 IEC 61727 VDE-AR-N-4105 UK (ER G83/1-1) EN 50438

Purpose Utility interface Utility interface

Utility interface /

type approval Utility interface Utility interface

Technologies All PV All All All

Frequency [Hz] 50 N/A 50 50 50

Size (A/phase) 144 14

Separate limits for

<16A, <75A, >

75A 16 16

Size (kW/kVA) 100 10

<11kW, <52kW, >

52kW 11 11

Voltage levels 400 LV LV 400 400

Power Factor

Standard curve:

lagging at >50%

power output

>20% output

power

Lagging

>0.9

(0.98/0.95 - new) 0.9

0.95 (<13.8kW),

0.9 (>13.8kW) 0.95 0.95

Leading

1

(0.98/0.95 - new) 1

0.95 (<13.8kW),

0.9 (>13.8kW) 0.95 0.95

Max step sizes

10% (units

>100kW)

10% (units

>100kW)

DC current injection

1% of rated

current

(0.5%)

1% of rated

current Not provided 20mA 0 (Not allowed)

Inform and Fit allowed Yes Various

Max short-circuit current Not defined Not defined

Times rated

current Not defined Not defined

Synchronous generators 8

Asynchronous generators 6

Inverters 1

VDE 4105 Standard power factor characteristic curve

2014/05/06 17

Comparisons (Protection)

2014/05/06 18


Protection

Islanding No No Not defined If required

Disconnect time <2.0s <2.0s <5s <0.5s Not defined

Abnormal voltage

Range 1 V < 0.5pu V < 0.5pu V < 0.8pu V < 0.9pu < 0.85pu

Disconnect time <0.2s <0.1s <0.2s <1.5s <1.5s

Range 2 0.5pu-0.85pu 0.5pu-0.85pu

Disconnect time <2.0s <2.0s

Range 3 0.85pu-1.1pu 0.85pu-1.1pu 0.8pu-1.1pu

Disconnect time Continuous Continuous Continuous

Range 4 1.1pu-1.2pu 1.1pu-1.35pu >1.1pu

Disconnect time <2.0s <2.0s <0.2s

Range 5 >1.2pu >1.35pu >1.15pu >114.7pu >1.15pu

Disconnect time <0.16s <0.05s <0.2s <1.5s <0.2s

Abnormal frequency

Range 1 <47.5Hz 50Hz±1Hz <47.5Hz <47Hz <47Hz

Disconnect time <0.5s <0.2s <1s / <0.2s <0.5s <0.5s

Range 2

50.5Hz<f<52Hz

(new) 50.2Hz<f<51.5Hz

Disconnect time

50% P_M per Hz

(new) 40% P_M per Hz

Range 3 >52Hz >51.5Hz >50.5Hz >51Hz

Disconnect time <0.5s <1s / <0.2s <0.5s <0.5s

VDE 4105 – Power curtailment

2014/05/06 19

• Included in RPP Grid Code

Comparisons (Protection)

2014/05/06 20


Reconnection time 60s

20s to 5min

(system

dependent)

5s for short

disturbances 3min

3 min for mech,

20s for inverters

10min of stable

power

Ramp rate

10% of power

(new) 10% of power

Disconnection

time can be

increased to 5s if

generator can

withstand network

reconnection at

180° out of phase

Comparisons (Synchronising)

2014/05/06 21


Synchronising parameters Automatic

Angle 20° ±10°

Frequency 0.3 Hz ±500mHz

Voltage 5% / 11.5V ±10%

Earthing

According to

SANS 10142-1

According to

60364-7-712 BS 7671

According to

60364-5-55

Short-circuit protection

According to

60364-7-712

According to

60364-7-712

Isolation and switching

According to

SANS 60947-2

According to

60364-7-712

Comparisons (Quality of Supply)

2014/05/06 22


QOS Measured POC POC/PCC POC/PCC Seems to be POC Seems to be POC

Flicker

NRS 048-2

(combined effect)

0.5 max due to all

generation is in

conflict with

IEC61000-3-3/11 IEC 61000-3-3 IEC 61000-3-3

Pst NRS 048-4 (new) 0.65 0.65 0.65

Plt NRS 048-4 (new) 1 1 1

RVC NRS 048-4 (new) 3% 4.00% 3.30%

Unbalance

6kW - 10kW

(4.6kVA - new) Desirable <4.6kVA ER P29

Commutation notches 5% (new) 5%

Current distortion (per

harmonic)

IEC 61727

(IEEE519)

IEC 61000-3-2/12

+ listed

IEC 61000-3-2,

class A

IEC 61000-3-2,

class A

Comparisons (Quality of Supply)

2014/05/06 23

Odd harmonics Distortion limit

3rd through 9th Less than 4,0 %

11th through 15th Less than 2,0 %

17th through 21st Less than 1,5 %

23rd through 33rd Less than 0,6 %

Even harmonics Distortion limit

2nd through 8th Less than 1,0 %

10th through 32nd Less than 0,5 %

Table 1 — Current distortion limit as a function of harmonics

(Source: IEC 61727:2004/IEEE519)

• Interharmonics?

Key decisions: NRS 097-2-1 Review

• Revision of NRS 097-2-1:

• Applicable up to 1MVA connected on LV

• Additional requirements for larger units, e.g.:

• Must be balanced multi-phase units

• Must be able to receive generation inhibit signals

• Incorporate VDE 4105 where appropriate, e.g.

• Overfrequency curtailment requirements,

• Power factor requirements.

2014/05/06 24

NRS 097-2-2: Type Testing

• This was where the fun started…

• Various documents:

• Basic descriptions and requirements, to

• UL 1741

• Traceability

• Testing environment descriptions

• Testing monitoring and accuracy

• Repetitions of tests

• Test certificates

2014/05/06 25

NRS 097-2-2: Type Testing

• Anti-islanding / Loss of mains;

• Synchronising to grid;

• Short-circuit protection;

• Short-circuit / fault current contribution;

• Tripping requirements for abnormal voltage and frequency;

2014/05/06 26

• The following type tests are required:

• Different tests from different documents

• DC current injection;

• Power factor;

• Reconnection after trip;

• QOS emissions;

• Step size/ramp rate adjustments (if included in requirements);

NRS 097-2-2: Type Testing Environment

• Basic Test requirements:

• Test result accuracy – as per main doc and manufacturer spec

• Testing environment – as per manufacturer spec

• Measurement accuracy and calibration of the testing equipment – suitable accuracy to confirm conformance and traceable calibration

• Product information – manufacturer to provide all requirements for correct installation as well as specified performance

• Test reports – ensure repeatability

• Simulated utility – detail, e.g. THD < 2.5%, system impedance etc.

• Measurement system requirements – uncertainty <50% of EUT accuracy and capable to confirm manufacturer’s stated performance

2014/05/06 27

NRS 097-2-3: Simplified Connection

• In line with international practices and CIGRE recommendations;

• Simplified connection decision tree:

• Less than 25% of NMD (ADMD);

• Dedicated connections;

• Less than 75% of upstream transformer size;

• Less than 15% of MV feeder peak load;

• Size vs. distance limitations.

2014/05/06 28


2014/04/16 29


2014/04/16 30


• Research:

• UCT – similar analysis to Herman-Beta Method for LV network design;

• 6 case studies;

• Voltage rise considered;

• Indications are that the simplified requirements are appropriate until further investigation;

• QOS impact not considered.

2014/05/06 31

NRS 097-2-4: Policies and Procedures

• Eskom draft documents:

• General matters that require attention to facilitate EG

• Metering will need to be upgraded

• All staff working on LV feeders will need to be trained

• Networks may need suitable notification

• Short-term policy for LV Connected EG:

• Safety of line men and contractors

• Performance of the system

• Single Customer To Single Transformer Connection

• Lockable isolator

• Multiple Customers Connected To a LV Feeder

• Not allowed at present2014/05/06 32


• SANS 10142-1 section 7.12:

• NOTE 2 This part of SANS 10142 does not cover the supply to an installation that functions in parallel with the main supply (co-generation). Amdt 6

• Aspects not covered by SANS 10142-1 is not – not allowed. It is just outside of the jurisdiction of SANS 10142-1 and the authority of a “registered person”. Other bodies such as Professional Engineers and Professional Technicians operate in this space that is not explicitly defined by the Electrical Regulations or SANS Standards.

• The UK wiring code is explicit in the meaning around “not covering” embedded generators, it state that it has to be done with the approval of the grid provider. The SANS 10142-1 does not state this explicit but discussions with the drafters of the text indicate that it is the intent of the code to allow the grid provider and the embedded-generator owner to come to an agreement on the matter.

2014/05/06 33


• List of basic technical requirements:

• Compliance to NRS 097-2-1

• Compliance to NRS 097-2-2 or equivalent

• Utility accessible lockable isolation switch to prevent the embedded generator feeding back onto the utility installation.

• Suitable notification at the Eskom point of supply and metering installation

• Basic tests to verify the normal safety function of the installation with the embedded generator installed.

• The balance of the customer installation carries a valid COC

• Sign-off by suitably qualified person, i.e. Professional Engineers or Professional Technicians

2014/05/06 34

Wiring Code

• SANS 10142-1:

• Parallel connection not covered;

• SANS 10142-3:

• Does not conflict or supersede SANS 10142-1;

• Only cover from the generator terminals to the customer DB;

• DC requirements in SANS 10142-1 to be upgraded;

• SABS discussion on adoption of international documents/wording.

2014/05/06 35

PLEASE NOTE

• SAFETY!!!

• Anti-islanding extremely important for utility personnel as well as public

• Australia – rumours of several PV installations that caused fires at residential homes;

• Also safety of emergency personnel, e.g. fire brigade

• Firemans’ switch (over and above current definition)

• Potential conflict identified in SANS 10142-series

• Insurance implications

• Make sure your unit complies with all relevant specifications!

2014/05/06 36

Conclusions

• We have come a far way since 2007:

• NRS 097-2-1 is being updated in line with international documents, based on international experience

• NRS 097-2-2 is being drafted in line with international documents

• NRS 097-2-3 being published

• We still have a lot to do…

• Policy aspects, e.g. tariffs, application processes, incentives, licensing vs. registration, data requirements etc.

• Type testing of generators – no SA laboratory equipped to do so.

• Wiring requirements: SANS 10142-3 in beginning stages.

2014/05/06 37

Thank you

nrs 097-series / grid code discussion - sasgi 097-series / grid code discussion: gerhard botha ......

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