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Zero phase sequence impedance TRF

Zero phase sequence impedance TRF

Zero phase sequence impedance TRF

(OP)
Hi All
Please can any one assist me. See attached diagram. I have a 6 MVA star/delta TRF that supplies an 11 kV bus. For a fault on the 11 kV bus I need to calculate the fault current using SYMMETRICAL COMPONENTS!! I understand how to determine the positive and negative sequence impedance in order to calculate the fault current on the 11kV bus, but do not have any idea how to calculate the zero phase sequence with the connected neutral earthing resistor. Any assistance will be appreciated.

RE: Zero phase sequence impedance TRF

Ohms law. Line to ground current on the delta side will be limited by the 30 Ohm resistor and the zero sequence impedance of the grounding circuit. The highest current will when the zero sequence impedance of the grounding circuit is ignored and the current calculated using just the 30 Ohms. For some applications this will be adequate.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Zero phase sequence impedance TRF

Blackburn's Symmetrical Components and Anderson's Analysis of Faulted Power Systems provide lots of information for performing symmetrical components calculations. Don't forget the '3'.

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