Question:-
Consider a stator winding of an alternator with an internal high-resistance ground fault. The currents under the fault condition are as shown in the figure. The winding is protected using a differential current scheme with current transformers of ratio 400/5 A as shown. The current through the operating coil is

Option (A)
0.17875 A
Option (B)
0.2A
Option(C)
0.375A
Option(D)
60 kA
Correct Option:
(C)
Question Solution:
Current through the operating coil= {(250 x 5) / 400} – {(220 x 5) / 400} = (3/8) = 0.375A
question-answer-faq-2288