In a test by Murray loop for ground fault on 600 m of cable having a resistance of 1.5 Ω/km, the faulty cable is looped with a sound cable of the same length and area of cross section. If the ratio of the other two arms of the testing network at balance is 3 : 1, find the distance of the fault from the testing end of cables.

• A. 100 m
• B. 200 m
• C. 400 m
• D. 300 m

Answer: (D)

Where,
d is distance in m
Q is value of variable resistor in ohm
P is variable resistance in ohm
Here Q/P = 1/3 is given,
d = Q/(P + Q)*Loop length
= 1/4*(2*600)
= 300 m