What is the purpose of measuring prospective short circuit current and earth electrode resistance?
Prospective short circuit current is the current that could flow in a circuit due to a short circuit of negligable impedance. In plain language how much current could flow due to a short circuit. Basically it is worked out by adding all the impedances on the circuit from the star point at the supply transformer along the active conductors to the point of the short circuit. Then the return path back through the earth conductor to the men point (the point where the neutral is connected to earth). Then via the neutral conductors back to the star point of the supply transformer. The supply voltage divided by the amount of impedance equals the prospective short circuit current. This is the current that could flow due to a short circuit. This is important as the current rises so quickly that say a 20 amp circuit breaker could actually have to switch 4000 plus amps by the time it finally breaks the circuit. THe breaker may start to trip just over 20 amps but by the time it finally breaks the
