Only I need P39 for the help Thanks Refer again to problem 3

Only I need P3.9 for the help.

Thanks.

Refer again to problem 3.8. Let us now assume that the impedance of the 138kV source is not negligible and that it ahs the same X/R ratio as the transformer itself. Let us further state that a symmetrical fault on the 138kV bus would develop a fault current of 18kA rms.

Determine the frequency and relative magnitude of the transient recovery voltage of the circuit breaker when it interrupts the fault described in problem 3.2

Assume that the stray capacitance on the source side of the breaker is 12,000pF.

Solution

as per asked related to qquestion 3.8

frequency = 1/2*pi(LC)^0.5

^{C = 5200 pF}

L = Pu valuec* base value

base value = (kV)² / MVA

= 9.5

L = 0.95

f = 3.26 kHZ