j0.2 For the following power system the impedance matrix is given below. Initially all bus voltages are 1 pu. Then a three-phase fault occurs at bus (2). j0.25 j0.2 (1) j0.1 (3) (a) What is the fault current? (2) j0.125 j0.1 (b) What are the post-fault bus voltages? 0.0625 0.02083 0.02083) Zbus i|0.02083 0.07044 0.02282 0.02083 0.02282 0.06091

If the source impedance at a 13.2 kV distribution substation bus is (0:5 + 1:5) Q per phase, compute the RMS and maximum peak instantaneous value of the fault current, for a balanced three-phase fault. For the system (X/R) ratio of 3.0, the asymmetrical factor is 1.9495 and the time of peak is 7.1 ms (see Problem 1). Comment on the withstanding peak current capability to which all substation electrical equipment need to be designed. Problem 1 Consider the expression for i(f) given by i(t) = v21ms [sin(@t-0-)+ sin 0,.eR/X)] where ez = tan-1 (WL/R). (a) For (X/R) equal to zero and infinity, plot i(f) as a function of (wf). (b) Comment on the DC offset of the fault current waveforms. (c) Find the asymmetrical current factor and the time of peak, tp, in milliseconds, for (X/R) ratios of zero and infinity.

the positive , negative and zero sequence reactance of a 20mva,13.8kv synchrounous generator are 0.3pu, 0.2pu,and 0.1 pu respectively. the generator is solidly grounded and is not loaded. a line to ground fault occurs on phase a. neglect all resistance,detirmine the fault current.

Q. when a three-phase fault occurs at 75% of the distance from bus G. This fault has 10 arc resistance. 100 MVA, 115 KV Line GH a-Assume that the angle of the mho characteristic is 70°.Determine if the zone I mho unit at H set for 90% of the line GH can operate for this fault. b-Determine the apparent impedance seen by the distance relays at H for this fault. G Z, = 0.365 Z83° - 80% l6 = 1.96 Z–31.42° 4 = 2.60 Z–47.76° ķ = 4.51 Z-40.68° All values in per unit on 100 MVA, 115 kV.