erickench said:
The earth should never be used as a ground fault current return path. I's resistance is too high and may therefore be unable to operate the overcurrent device in case of a fault.
Dear Erickench ;
1 – Excuse-me to say, I can't understand where the Earth Fault will be circulated, asume that we use ” TN-C ” as Earthing System, that means ” 4 Wires : L1, L2, L3, PEN “, or we use ” TN-S ” that means ” 5 wires : L1, L2, L3, N, PE “, and in both the earth fault is with ” L2 “, please let me know where the Earth Fault Current will be circulated ?
2 – Normally, once we have an ” Earth Fault “, and accordignly to the Earthing System, we have 2 possibilities to trip the Circuit Breaker that are :
A – Use the ” Magnetic Protection ” built-in the Circuit Breaker, if the value of the Earth Fault Current is bigger than the setting of this protection, or, if possible, modify the setting to be smaller than the Earth Fault Current.
B – Use an ” Earth Leakage ” Protection when we can't realize any condition mentioned in A.
Noting that :
– We can use the ” Earth Leakage Protection ” with ” TN-S ; TT ; IT “.
– We can't use the ” Earth Leakage Protection ” with ” TN-C “.
– The value if the ” Impedance Fault Loop ” is big ” … Ω “ in ” TT ” and ” IT with many different Earth Points “, where in these cases the Earth Fault Current's value is small and we should use the Earth Leakage Protection to trip the circuit breaker.
Regards.