Connect 5v to one wire and the relay to the other. When you throw the switch measure the time between when the switch was thrown and when the relay activates. Subtract the time taken for the relay operation lag and using that time calculate the distance the electricity traveled by multiplying the time by speed of electricity through wire, divide by two and there is the distance to your fault.
(Above explanation based on available information given and circuit supplied)
Sorry to those upset by this answer but it makes as much sense as the question