Question

Bus A Bus B R1 TI ine 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) For parts (a) to (d) assume that the transformer impedance is equal to the transformer leakage reactance. 2) For parts (a) to (d) assume that the transformer zero sequence impedance is equal to the transformer positive sequence impedance. 3) For parts (a) to (d) assume that the source negative sequence impedance is equal to the positive sequence impedance (that is, we are electrically far away from the generators). 4) 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°). 5) The source zero sequence impedance is purely reactive. 6) Zero pre-fault current (that is, the pre-fault voltage is assumed to be 1.0 pu). Please use a system MVA base of 100 MVA for your per-unit calculations Assignment questions: (a) Calculate the source (that is, looking into the network from Bus A) positive, negative and zero sequence impedances, including the source earthing resistance (R)

Answer 1

posilve impedauce 3 4.13 3. 3 s 100 413 (PU) 2 86 3. 3