nicole segal -short circuit presentation - to's

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Generation Interconnection Short Circuit Analysis

PJM PlanningGeneration - PlanningNicole U. Segal

May 18, 2009


Presentation Overview

I. Short Circuit Software and Case Conversion Options

II. Short Circuit Queue Case Creation

III. PJM Modeling Assumptions

IV. Short Circuit Results Breakdown

V. Differences Between Feasibility and Impact Studies


ASPEN Short Circuit SoftwareOneLiner V3.1

• Short circuit and relay coordination program which PJM uses to model the transmission network and generation interconnection projects

Case Comparison V10.9

• Compares two cases and creates a difference file known as a CHF

Breaker Rating Module (BRM) V9.11

• Used to check the rating of circuit breakers against the short circuit fault currents

• Adheres to ANSI/IEEE for both total-current and symmetric-current rated breakers


ASPEN Case Conversion Options

Table 1: 2009 Software Conversion Options and File Types

Software File TypeCAPE .DXT or .RAW, .SEQPTI PSS/E .RAW, .SEQANAFAS .ANAGE Short Circuit .SEQGE Power Flow (PSLF) .EPC


ASPEN- CAPEResult Differences

Isolated Buses• CAPE recommends excluding isolated buses from the case

Phase Angle Inconsistencies• This problem can be fixed by going over each of the loops and

correcting the transformer implicit angle

XFMRs can be identified incorrectly as Y-Y instead of Y-Δ• For each loop check to see if any of the transformers have their

winding types incorrectly specified • Fixing one-loop will cause subsequent (multiple) loops to be fixed

ASPEN always includes XFMR Off-Nominal (fixed) Taps • This problem can be fixed in the initialization of the CAPE program


Example of ASPEN-CAPE Discrepancies

Nominal Taps

Off-Nominal Taps

3LG 1LG 3LG 1LGASPEN n/a n/a 12784 A 14157 A

CAPE Converted from PSS/E

12428 A 13864 A 12786 A 14159 A

CAPE Convertedfrom ASPEN

12433 A 13876 A 12790 A 14171 A

Table 2: Comparison of Fault Results for a 69 kV Bus


Short Circuit Queue Case Creation


RTEP Base Case Model

• 5 year short circuit baseline

• Short circuit models from our T.O. and neighboring systems included

• Model should include all planned transmission system upgrades

• Model should include all planned generation projects that have proceeded past the Impact Study phase

• The system impacts of these projects have already been studied• Reinforcements for these projects are included in the case

• Beginning with the 2014 base case PJM will monitor all circuit breakers rated 100 kV and greater


Generation Interconnection

• Model queue projects individually on the 5 year RTEP case• Study New Generation ≥ 30 MW• Verify data and case models for all upgrade projects• Projects connecting to ≤ 69 kV are not studied• Projects ≤ 10 MW are not modeled

• Each Queue is studied on a “Locked Case ” • Projects and upgrades for withdrawn projects are removed

until the case is locked

• If a circuit breaker is found to be overstressed, PJM communicates this to the transmission owner for them to verify the results and provide an upgrade plan.


Short Circuit Modeling Assumptions


Network Model Assumptions

1. Model Generators using X’’d(v)• Major sources of fault current• All Generators are online • Effects are localized (approx. 3 buses away)

2. Model lines & transformers using Z & Z0• Transformer winding connections

(e.g. delta, grounded wye)• Model zero sequence mutual coupling

3. Ignore loads, positive sequence shunts, & line charging

4. Flat-Start Voltage profile• Voltages at nominal


X/R Modeling Assumptions

Assumed X/R Reference

Lines X/R = 10 Typical Value

Generators X/R = 120 Typical Value

Transformers X/R = 60 Highest Point on XR curve therefore conservative

All X/R ratios are taken from IEEE C37.010

Table 4: X/R Assumptions

Better than letting ASPEN assume R =0.0001 p.u.


Zero Sequence Impedance Assumption

Table 5. Zero Sequence Impedance Assumptions

Assumed Zero Sequence

Lines Z0 = 3 * Z+

Underground Cable Z0 = 2 * Z+

Transformers Z0 = Z+

• Lines and Cables are unique this is a best guess estimate

• Most Transformers are Shell Type• Shell Z0 = Z+

• Core Z0 = 0.85 * Z+


Zero Impedance Line Assumption

Zero Impedance Line Model

Z = 0.00001 + j 0.0001 p.u.

• Connects the new generation to the substation or to a tapped line

• Allows for the maximum amount of fault current to be transferred to the system

• Gives the most conservative result (worst case scenario) when running the breaker program


Wind Turbine Model

Aggregate Generator

Aggregate Unit Transformer

Main GSU

Transmission Line or Cable

Zero Impedance Line


Short Circuit Results


New Over Duty Breaker

Breaker(s) with a maximum short circuit interrupting duty greater than 100%

Contribution to Previously Identified Over Duty Breaker

Breaker(s) with short circuit interrupting duties greater than 100% and with the addition of the queue project have an increase of 3%

Result Definitions


Short Circuit Results

DutyPercent

With #023

DutyPercentWithout

#023

DutyPercent

DifferenceNote

117.30% 68.90% 48.40% New Overduty

105.60% 101.30% 4.30% Baseline- No Cost Allocation

104.70% 102.80% 1.90% Over 100%, < 3% contribution

100.00% 99.90% 0.10% -

138.20% 134.40% 3.80% Over 100%, > 3% contribution


1. Identify all New Over Duty Breakers

2. Obtain Upgrade Plan for New Over Breakers from T.O.

• Includes new breaker rating(s) , cost and time estimate for

replacement/upgrade

3. Identify all Contributing Breakers

4. Verify all Lower kV (100 kV and below) Breakers

• Obtain Upgrade Plan from T.O. if necessary

Results


Differences Between Feasibility and Impact Studies


Feasibility Study:

• Approximate data from developer is used to create models• Cables for wind projects are not modeled• Lines are modeled as zero impedance line• Line, Transformer, and Generator X/R assumptions are used• LTAP are created at 50% on line between 2 substations

Impact Study:

• Final Data from developer is used to create models• Reinforcements for Queue project are included in models• Cable for Wind Projects are modeled if supplied• Lines are modeled using Z from T.O. or Developer• LTAP are created at the actual POI

Modeling Differences


Resources

Breaker Interrupting Rating

• Total Current Rating (MVA) (IEEE C37.5)

• Symmetrical Rating (kA) (IEEE C37.010)

Planning Process Manuals

• Manual 14A ― Generation and Transmission Interconnection Process

• Manual 14C ― Generation and Transmission Interconnection Facility Construction

http://www.pjm.com/documents/manuals/rtep-process-manuals.aspx

http://www.pjm.com/documents/manuals/rtep-process-manuals.aspx


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