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WECC Short Circuit Analysis

Update: WECC Staff Short Circuit Modeling Zach Garrard, Tyson Niemann

W E S T E R N E L E C T R I C I T Y C O O R D I N A T I N G C O U N C I L

Overview• Purpose• Scope• Methodology

– Flow Chart– Key Identifiers– Limitations

• Entity Feedback– Interpreting Results– Comparisons– Scoring and Sorting

• Findings– Plots– Statistics

• Project Observations– Entity Feedback– Lessons Learned– Recommendations– Study Benefits

• Event Based Model Validation

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Purpose

• Improve Western Interconnection Reliability– Assess the consistency of short-circuit models within

the Western Interconnection • Examine differences caused by the use of different software

tools and conversion methods• Compare fault calculations of neighboring utilities at the

same bus locations– Provide information to the Short Circuit Modeling

Work Group (SCMWG) to help direct their scope and actions of work

– Facilitate the coordination of short circuit models in sub-regional planning groups and amongst both planning and protection engineers throughout WECC

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Scope

Analytics

Model conversion qualityEntity neighbor consistency Short circuit model settings

Data Sharing

Difficulty sharing neighboring modelsSoftware package modeling differencesSoftware model conversion

Coordinating

Planning vs Protection coordinationSub-Regional Planning Group member coordinationWECC involvement in short circuit modeling

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Methodology: Flow Chart7


Methodology: Key Identifiers

• Many Short Circuit models do not require bus number assignments for each bus, so “Key Identifiers” were assigned to each bus for use in matching. – All letters in the bus name were capitalized– Any spaces in the bus name were removed

• For example:

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Bus Name Bus Nominal kV Key Identifier

Taggard 230 TAGGARD230

Gold Hill 500 GOLDHILL500

~NORTH_POINT 345 ~NORTH_POINT345

Methodology: Limitations

• Non-matched bus name “Key Identifiers” (e.g. “TAGGARD230” and “TGD230” are the same bus represented in two cases)

• No consistent bus numbering scheme widely implemented

• Fault duties compared limited to bus faults• Buses <230kV were not included• Conversion errors between CAPE/ASPEN/PowerWorld• Cases are built for different studies• Very few submitted seam locations for comparison

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Entity Feedback


Interpreting Results11


• Conversion Quality Analysis– Each case was converted to the remaining other two

programs, and the calculations were then compared in an Excel spreadsheet

• Comparison Analysis– Each entity fault calculations were matched (by Key

Identifier) to neighboring entity fault calculations and the results were compared bus by bus

• Scoring and Sorting– The results of each entity’s comparison analysis were

summarized in “Scorecards” for each entity’s neighbors and the results were sorted from the entity with the highest inconsistency levels to the lowest

Conversion Quality Analysis: Format

• Faults are run in each program for each case and the results are compared between an entity’s own buses

• Percent standard deviation between the three Programs

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Comparison Analysis: Format13


• Fault calculations compared to neighboring entities

Scorecards: Format14


Sorting: Degree of Inconsistency15


Findings


Short Circuit Modeling Software Utilization in WECC

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Aspen82%

CAPE10%

PowerWorld 5%PSS/E

3%

Neighboring Entity Perspective18


3 Phase Faults (ASPEN)

Median 15.36%

Average 28.04%

>25% 10-25% <10%

500kV 148 133 1882

345kV 558 535 3697

230kV 795 1029 8069

Totals1501 1697 13648

8.9% 10.1% 81.0%

148 133

1882

558 535

3697

7951029

8069

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

>25% 10-25% <10%

Num

ber o

f Bus

es

3 Phase Faults by Percent Difference

500kV 345kV 230kV

• 20,344 total buses > 230 kV among all cases

• These percentages represent percent differences between neighboring cases

Western Interconnection Perspective20


3 Phase Faults (ASPEN)

Median 1.25%

Average 5.40%

>25% 10-25% <10%

500kV 49 37 636

345kV 58 85 573

230kV 92 241 2723

Totals199 363 3932

4.4% 8.1% 87.5%

49 37

636

58 85

573

92241

2723

0

500

1000

1500

2000

2500

3000

>25% 10-25% <10%

Num

ber o

f Bus

es

3 Phase Faults by Percent Difference

500kV 345kV 230kV

• 4,494 buses were modeled in more than one case

• These percentages represent the percent standard deviation

3PF Fault Current by Voltage Level21


3PF Fault Distribution Curve22


% of CAPE values > ±10% is 10.23%> ±25% is 4.23%

% of PowerWorld values > ±10% is 0.433%> ±25% is 0.295%

1LG Fault Distribution Curve23


% of CAPE values > ±10% is 10.37%> ±25% is 4.28%

% of PowerWorld values > ±10% is 4.24%> ±25% is 2.70%

StatisticsAll statistics represent buses modeled at 230 kV and higher and were matched using

Key Identifiers.• There were 20,344 total buses modeled in the submitted WI short circuit cases.• There were 7,223 unique buses modeled in the submitted WI short circuit cases.• 1,163 of these buses were matched to the 2017 WECC Operating Base Case.• 547 of the unique buses submitted were matched to the West Wide System Model.• Approximately 638 boundary buses were found between neighboring entities.• On average, entities in the WI are modeling 33.78% of their neighboring entities’ system.• 62.22% of unique buses submitted are modeled by two or more entities.

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Statistics Cont.• On average, the single line to ground fault calculation for a bus is higher than its three phase fault calculation 23% of the time.

• When single line to ground calculations that are greater than their three phase calculations, they are higher by 14%, on average.

• On average, the percent standard deviation between three phase fault calculations for the same bus in a given case between the three studied software programs was 6.14%.

• On average, the percent standard deviation between single line to ground fault calculations for the same bus in a given case between the three studied software programs was 7.1%.

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Project Observations


Entity Feedback

• Regional planning groups are “stepping on each other’s toes”– Lacking enough coordination with neighboring

planning groups.• Potential disconnect between entities and their

planning groups– Be notified of meetings so that they can be more

involved• A significant amount of time spent converting

between programs

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WECC Lessons Learned• Analytical:

– Inconsistencies found throughout the Western Interconnection– Naming convention is not consistent between entities– No widely established bus numbering system– Settings can have a big impact on calculations– More specific in our data requests in the future (e.g. file format,

seam locations, etc.)• Data Sharing and Inter-Regional coordination:

– Disconnect between planning and protection groups– Planning and protection groups have their own short circuit

models within entities– Sharing between entities is challenging

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Recommendations• Entities

– Implement the findings of WECC’s analysis to aid them in coordinating their short circuit models with their neighbors

– Participate in the SCMWG and the Relay Work Group– Encourage Planning and Protection to meet with each

other• Sub-Regional Planning Groups

– Establish naming conventions for buses used in multiple models

– Consider using the Data Preparation Manual to assign bus numbers in short circuit models by area similar to stability planning cases

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Recommendations Cont.

• Sub-Regional Planning Groups – Verify that each of their entities are included in

group discussions and ensure that all entities are included in a sub-regional planning group.

– Encourage further coordination between their planning engineers and their protection engineers.

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WECC Study Benefits

• Aspen OneLiner Improvements– The feedback given to Aspen developers has

already helped identify several errors in the Aspen to .RAW conversion which are being addressed

– Aspen now intends to meet with CAPE developers to coordinate fully supported cross-platform .DXT file usage

– Aspen is willing to meet with the SCMWG to further resolve entity concerns and work with other platform developers

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WECC Study Benefits Cont.

• Model Coordination Improvements– Early feedback from entity participants indicates

they are actively working with their neighbors to improve short circuit model consistency

– Sub-regional planning and modeling groups will use the results of the study to discuss group wide coordination strategies

– Protection and planning engineers are becoming more aware of each other’s short circuit modeling needs and communication is improving

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Model Validation Example

• Reported Event Cat 1a• Date: 2011• Time: Morning• 230-kV line tripped by relay operation, due to an

vehicle striking the line.• B-C phase fault 0.4 miles from the closest sub, a

hydro facility.• Slightly over 10,500 Amps “B to C” phase fault

measured from the facility.

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Model Validation Ex: Aspen34


Event Study Request

• What– Detailed examples of fault events to perform

model validation on entity cases– Detailed examples of events or misoperations that

happened due to incorrect short-circuit modeling errors/inconsistencies

• Why– To perform more short circuit model validation

testing and trend how many system misoperations on average are due to modeling problems

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Comments

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• Kent Bolton (Lead) [email protected]• Tyson Niemann [email protected]• Zachary Garrard [email protected]

mailto:[email protected]



Additional Slides


Aspen Settings38


Aspen Settings39


Aspen Settings40


Cape Settings41


Cape Settings42


PowerWorld Settings43


PowerWorld Settings44


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