Question

Bus A Bus B R1 T1 line 1 20% 80% line 2 T2 R2 110 kV 11 kV The fault is located at point F, which is 20% of the total line 2 length from Bus B Fault MVA 1524.20471 Three-phase fault level in MVA at bus A SPFL (kA) 8 MVA1 MVA2 X1 (96) X2 (96) R1 (2) R2 (Q) z' (Q) Zo (2) Rf (Q) Single phase to ground fault level (kA) at bus A Transformer 1 MVA rating Transformer 2 MVA rating 50 50 6.0 5.5 u. impedance for transformer 1 u. impedance for transformer 2 Neutral earthing resistor of transformer T1 Neutral earthing resistor of transformer T2 Positive sequence reactance of transmission lines (Line 1 and Line 2) Zero sequence reactance of transmission lines (Line 1 and Line 2) Fault resistance for phase to ground fault 1 5+j10 40 Generic Network Data 1) Bus A nominal voltage 110 kV 2) Bus B nominal voltage 11kV 3) Transformer vector group Dyn5 (for both transformers) 4) Line 1 and line 2 have the same impedance values 5) For a single phase to ground fault at bus A, the fault current lags the pre-fault voltage (at the bus) by 70 degrees Assumptions: 1) The three-phase fault current at Bus A is purely reactive (that is, for a three-phase bolted fault at Bus A, the fault current lags the source voltage by 90°) 2) The source zero sequence impedance is purely reactive 3) Zero pre-fault current (that is, the pre-fault voltage is assumed to be 1.0 р.u.). Please use a system MVA base of 100 MVA for your per-unit calculations. Assignment questions: (e) For phase to ground fault, with a fault resistance of Rf, (given in your network data provided on the course study desk) at location F, calculate the magnitude and phase angle of the transmission line currents flowing away from bus B in the faulted line. Use the given line to neutral pre-fault voltage at bus A as the reference. Assume phase 'a' is the faulted phase.

Answer 1

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