If an unsymmetrical fault occurs on phase C of a transmission line, what would make the fault symmetrical? A. if phase C of the transmission line opens B. If phases A and B become faulted C. If two different faults occur on phas a and b

13. _______ current attempts to return to the source over any available conductive path.A. DirectB. AlternatingC. Ground-faultD. Arc-fault

Please solve Q1(C) ONLY. Q1(A) is for reference.

Explain the concept of fault analysis in power systems. How is fault current calculated, and what protection mechanisms are in place?

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.

(b) A 30000 kVA, 13.8 kV generator with X = 18% is connected to a bus which supplies two identical motors as shown in the Figure 2. The subtransient reactance X of each motor is 25% on a base of 6000 kVA, 7 kV. The bus voltage at the motors is 7 kV when a three phase fault occurs at the point P. For the fault specified, determine (a) the subtransient current in the fault (b) the subtransient current in breaker A and (c) the symmetrical short circuit interrupting current in the fault and in breaker A. юю DO A P 0-0 Gen. Figure 2 Motors

In a short circuit test on a 120 kV, 3 phase system, the breaker gave the following results: p.f. of fault 0.6, recovery voltage 0.9 times full line voltage, breaker current symmetrical, and restriking transient had a natural frequency 12 kHz. Determine average RRRV. Assume fault is grounded.