Buried Tertiary Rating & Impedance
Buried Tertiary Rating & Impedance
(OP)
We are trying to calculate some fault currents for a substation with a three-winding transformer that includes a buried tertiary. There is no data on the nameplate or in the test report regarding the impedances related to the tertiary winding or its kVA rating. I presume this is not required since the winding has no leads brought out.
Is there some reasonable approximation that can be made as to the impedance between the tertiary (4160 V) and primary (115 kV) winding?
Is there some reasonable approximation that can be made as to the impedance between the tertiary (4160 V) and primary (115 kV) winding?






RE: Buried Tertiary Rating & Impedance
RE: Buried Tertiary Rating & Impedance
RE: Buried Tertiary Rating & Impedance
prc - MVA rating is 15/20/25, High side is 105 kV. Low side is 34.5 kV Impedance H-X is 8.5%
Thanks,
dpc
RE: Buried Tertiary Rating & Impedance
RE: Buried Tertiary Rating & Impedance
Yes, it's an ANSI rated unit - 8.5% @ 15 MVA. Thank you very much for your assistance. I appreciate it.
Best Regards,
Dave
RE: Buried Tertiary Rating & Impedance
Can you please share, how did you calculate the various impedance?
RE: Buried Tertiary Rating & Impedance
RE: Buried Tertiary Rating & Impedance
"The estimated positive sequence impedances at 15MVA base are
LV-TV = 3.63%
HV-TV = 13.60%
The estimated zero sequence impedances at 15MVA base are
LV-TV = 3.42%
HV-TV = 12.27%"
RE: Buried Tertiary Rating & Impedance