The Earth Fault Loop includes the Load, the bonding conductor, the earthed (Grounded) neutral point of the tranformer, the source line winding and the live conductor from the source to the load.
The earth fault loop impedance verification is performed to prove the correct operation of the protective device in order to protect in caso of indirect contats. The aim is to check that, in case of a ground fault, the related fault current is strong enough to cause the action of the protection device, breacking the power supply.
In order to achieve a proper fault corrent value, the impedance of fhe fault loop should be lower than a specific value. According to EN 60204-1 standard, in case of TN system, the measurement should be performed using a loop tester, which must comply the IEC 61557-3.
During the test the system should be under normal operating conditions, so each load should be energised. The instrument should be connected between the live conductor and the bondig conductor of the e