PGDTF,

Here are the questions Oncor submitted to Siemens PTI with the answers provided by them in red font:

1. Should all substations be modeled so that each branch calculation can be made, or is it only necessary to model stations containing a high side wye grounded transformer or shunt device?

            Yes. Modeling each substation will produce a more accurate calculation of the GICs.

2. If stations that do not contain high side wye-grounded transformers or shunt devices need to be modeled, is the station grounding resistance needed or just its latitude and longitude?

If substation has no grounded connection, then resistance data will not be used. So let PSSE assume the default data for those substations. For every substation you need to provide its latitude and longitude.

3. If you provide a Transmission Line Model with only BUSI, BUSJ, CKT, RBRN = 0, INDVP = 0 and INDVQ = 0 to identify a pipe-type underground transmission line, will the program convert the ac power flow resistance to a dc resistance?

Yes. For both transformers and transmission lines, if you do not provide dc resistance, dc resistance is calculated from power flow data (ac).

4. If you provide no other Transmission Line Models except for the underground lines, will the resistance for all other lines from the ac base case be automatically converted to dc resistance?

Yes


Thanks,



Michael Juricek, P.E.

Senior Manager, Transmission Planning

Assets Planning Distribution and Transmission
Oncor Electric Delivery Co LLC
Office: 214.743.6671
Mobile: 214.490.0748

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