9 advanced lf topics

7/29/2019 9 Advanced LF Topics

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Section 9Advanced LF Topics

Load Flow Convergence

Voltage Control

Mvar Control


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Load Flow Convergence

Negative Impedance Zero or Very Small Impedance

Widely Different Branch Impedance Values

Long Radial System Configurations

Bad Bus Voltage Initial Values


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Voltage Control

Under/Over Voltage Conditions must befixed for proper equipment operation andinsulation ratings be met.

Methods of Improving Voltage Conditions:

Transformer Replacement

Capacitor Addition

Transformer Tap Adjustment


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Under-Voltage Example

Create Under VoltageCondition

Change Syn2 Quantity to 6.(Info Page, Quantity Field)

Run LF

Bus8 Turns Magenta (UnderVoltage Condition)

Method 1 - Change Xfmr

Change T4 from 3 MVA to 8MVA, will notice slight

improvement on the Bus8 kV

Too Expensive and timeconsuming

Method 2 - ShuntCapacitor Add Shunt Capacitor to Bus8

300 kvar 3 Banks

Voltage is improved

Method 3 - Change Tap

Place LTC on Primary of T6

Select Bus8 for Control Bus

Select Update LTC in theStudy Case

Run LF

Bus Voltage Comes withinspecified limits


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Mvar Control

Vars from Utility

Add Switch to CAP1

Open Switch

Run LF

Method 1 Generator

Change Generator fromVoltage Control to MvarControl

Set Mvar Design Setting to 5Mvars

Method 2 Add Capacitor

Close Switch

Run Load Flow

Var Contribution from the

Utility reduces

Method 3 Xfmr MVA

Change T1 Mva to 40 MVA

Will notice decrease in thecontribution from the Utility


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Panel Systems


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Panel Boards They are a collection of branch circuits

feeding system loads

Panel System is used for representing powerand lighting panels in electrical systems

Click to drop once on OLV

Double-Click to drop multiple panels


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A panel branch circuit load can be modeled as

an internal or external load

Advantages:

1. Easier Data Entry

2. Concise SystemRepresentation

Representation


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Pin 0 is the top pin of the panel

ETAP allows up to 24 external load connections

Pin Assignment


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Assumptions

Vrated (internal load) = Vrated (Panel Voltage)

Note that if a 1-Phase load is connected to a 3-Phase panel circuit, the rated voltage of the panel

circuit is (1/3) times the rated panel voltage

The voltage of L1 or L2 phase in a 1-Phase 3-Wirepanel is (1/2) times the rated voltage of the panel

There are no losses in the feeders connecting aload to the panel

Static loads are calculated based on their ratedvoltage


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Line-Line Connections

Load Connected Between Two Phases of a

3-Phase System

A

B

C

Load

IBCIC = -IBC

A

B

C

LoadB

IB = IBC

Angle by which load current IBC lags the load voltage =

Therefore, for load connected between phases B and C:

SBC = VBC.IBC

PBC = VBC.IBC.cos

QBC = VBC.IBC.sin

For load connected to phase B

SB = VB.IB

PB = VB.IB.cos ( - 30)

QB = VB.IB.sin ( - 30)

And, for load connected to phase C

SC = VC.IC

PC = VC.IC.cos ( + 30)QC = VC.IC.sin ( + 30)


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3-Phase 4-Wire Panel




NEC Selection

A, B, C from top to bottom or

left to right from the front of

the panel

Phase B shall be the highestvoltage (LG) on a 3-phase, 4-

wire delta connected system

(midpoint grounded)

Info Page


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Intelligent kV CalculationIf a 1-Phase panel is connected to a 3-Phase bus

having a nominal voltage equal to 0.48 kV, the

default rated kV of the panel is set to (0.48/1.732

=) 0.277 kV

For IEC, Enclosure Type

is Ingress Protection(IPxy), where IP00 means

no protection or shielding

on the panel

Select ANSI or IEC

Breakers or Fuses from

Main Device Library

Rating Page


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Schedule Page

Circuit Numbers with

Column Layout

Circuit Numbers with

Standard Layout


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Description TabFirst 14 load items in the list are based on NEC 1999

Last 10 load types in the Panel Code Factor Table are user-defined

Load Type is used to determine the Code Factors used in calculating the totalpanel load

External loads are classified as motor load or static load according to the

element type

For External links the load status is determined from the connected loads

demand factor status


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Rating Tab

Enter per phase VA, W, or

Amperes for this load.

For example, if total Watts

for a 3-phase load are

1200, enter W as 400

(=1200/3)


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Loading Tab

For internal loads, enter the % loading for the selected loading category

For both internal and external loads, Amp values are

calculated based on terminal bus nominal kV


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Protective Device Tab

Library Quick Pick -LV Circuit Breaker

(Molded Case, with

Thermal Magnetic Trip

Device) or

Library Quick Pick Fuse will appeardepending on the

Type of protective

device selected.


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Feeder Tab


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Action Buttons

Copy the content of the selected

row to clipboard. Circuit number,Phase, Pole, Load Name, Link

and State are not copied.

Paste the entire content (of the

copied row) in the selected row.

This will work when the Link

Type is other than space or

unusable, and only for fields

which are not blocked.

Blank out the contents of the entire

selected row.


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Summary Page

Continuous Load Per Phase and Total

Non-Continuous Load Per Phase and Total

Connected Load Per Phase and Total (Continuous + Non-Continuous Load)

Code Demand Per Phase and Total


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Output Report


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Panel Code Factors

Code demand load depends on Panel Code Factors

The first fourteen have fixed formats per NEC 1999

Code demand load calculation for internal loads are done

for each types of load separately and then summed up

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