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Export ASPEN Sequence Data To PTI WECC Base Case

Puget Sound Energy: Shengli Huang, Senior Engineer & PE Joe Seabrook

Alberta Electric System Operator: Pamela Mclean

May 14, 2013 revised May 21, 2014

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The Covered Topics

1. Background Recommendation (Pamela Mclean)

2. Steps to Export ASPEN Sequence Data to PTI WECC Base Case (Shengli Huang) (Assumes you have not arrived to the Alberta gold standard of matching bus numbers.)

3. Questions Needing to Be Discussed

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1. Background Recommendation for The Work

(Pamela Mclean) The default here in Alberta has been to use bus-numbers in ASPEN and keep them lined up with the power flow base cases. When they started to drift apart in the early 2000s it immediately caused process problems and we intervened to get them synced up again. I think all utilities are well-advised to do this.

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2. Steps to Export ASPEN Sequence Data to PTI WECC Base Case

(1)Open the latest ASPEN Oneliner Case. This case has detailed sequence data and relay data.

(2)Pre-Process the Case: You might consider deleting relay data, filtering out other regions’ devices, only keeping the devices with your company’s ownership and the bordering devices.

(3)Open a PTI WECC Case used for comparison. This is the target case you try to get sequence data.

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2a. Steps to Export ASPEN Sequence Data to PTI WECC Base Case (The Mclean

Alternative)A. Export power flow data from ASPEN in PTI “RAW” format

B. Export sequence data from ASPEN in PTI “SEQ” format (ASPEN can also export sequence data to GE PSLF, the process should be similar)

C. Open PSS/E and read in RAW to create a PSS/E version of the ASPEN case

D. Use PSS/E “DIFF” functionality to compare the PSS/E  version of the ASPEN case with the WECC case. DIFF allows you to use *either* bus-names or bus-numbers for matching so if you’ve been using bus-names in ASPEN you would do your matching on that.

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(4) Trace down each line, transformer, generator, Switch Shunt… in PTI Target Case and compare it to the one in ASPEN Case. Our experience shows the following differences could exist in both cases:

(4.1) No bus number for ASPEN case Get Bus Number

(4.2) Bus number doesn't match each other Match ASPEN’s one to PTI Case

(4.3) Device ID Match ASPEN’s one to PTI Case

(4.4) Device configuration Found why and might either one of ASPEN or PTI

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(5) Demonstrate: (1) Branch in PTI Case: Sedro (42100)-Horse Ranch Tap(42321)

(Branch ID 1) Get Bus Number for S Horse Ranch Tap(42321) for one in ASPEN ;

(2) 3-Winding Transformer in ASPEN: Sedro 230kV(42100)-Sedro 115kV(42120)-TertTiary(xxxxx) Get bus number to Tertiary Bus (942100) in ASPEN; revise 2-Winding Transformer in PTI to 3-Winding Transformer: create Tertiary Bus (942100) first in PTI.

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(6) After The Target devices in ASPEN are modified to match Ones in PTI case, save ASPEN case as PTI Raw file and seq file:

(1) Go to ASPEN File Export Network Data: select Export network data of entire network and Output Data format as PTI PSS/E.

(2) Click the Ok Button then a popup window will show up, then select the PTI version you are using, and specify “the first fictitious bus number for 3-winding transformer middle points and first bus number for the buses with no bus numbers (the reason is that ASPEN emphasize bus names, not bus numbers, which means lots of buses have no bus numbers, especially distribution buses);

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Cautious: Don’t specify those bus numbers close to existing bus numbers, otherwise they will cause conflicts. Such as: 6 digit numbers starting with 900000 for the buses with no bus numbers (Most are distribution buses including 3-winding transformer’s tertiary buses) and 6 digit numbers starting with 100000 for 3-winding transformer middle point buses.

(7) Then you will be asked to get the file name for PTI raw file and PTI sequence file so those two files can be saved.

(8) Then go to PTI, import just saved seq file into case. You will see the R0 and X0 data will imported into the corresponding field of lines, 2-W and 3-W transformer, generator’s data sheets.

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(9) The Future Case Update: Two Ways to Update: Way No.1:

Run ASPEN’s case Comparison Tool in the ASPEN drive and compare the latest case with old case, save the change information as change file (CHF file).

Open ASPEN and load the old case, run change file (CHF file), the old case will be updated to the latest one. And then follow above Steps export the sequence data.

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Way No.2: read the change information following step (1) when comparing the latest case with old case. Then go to old case to manually change those devices. Usually, the change will not be too much and information is very clear. So it is easy to follow that information to change the case directly.

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(1)What rules should we follow to assign bus number for the tertiary bus of 3-winding transformer?

(2) Should utility companies coordinate their protection engineers to match ASPEN Base’s Bus number with WECC Base’s ones? If it can be done, two cases will be aligned up, will save lots of time for us.

(3) The additional finding: ASPEN Case has the detailed

distribution transformers and feeders’ data which could be used to replace the equivalent transformer and feeder in WECC Composite Load Model.

3. Questions Needing to be Discussed

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Any Questions?

If you have trouble exporting sequence data, Please feel free to contact us:

Shengli Huang: Shengli.Huang@PSE.com; (425) 456-2769

Joe Seabrook : Joe.Seabrook@PSE.com; (425) 462-3577

Pamela Mclean : Pamela.Mclean@aeso.ca; (403) 539-2606