ABSTRACT
This chapter talks about the earth fault loop impedance tester that is used for earth fault loop impedance testing. The loop impedance tester functions by creating, in effect, an earth fault for a brief moment, and connected to the circuit via a plug or by flying leads connected separately to line, neutral and earth. The instrument should allow an earth fault to exist for a maximum of 40 ms, and resolution of 0.01 V is adequate for circuits up to 50 A. In earth fault loop path, overcurrent protective devices, under earth fault conditions, disconnect fast enough to reduce the risk of electric shock. This is achieved if the actual value of the earth fault loop impedance does not exceed the tabulated maximum values given in the relevant parts of the IET Regulations. The purpose of the test is to determine the actual value of the loop impedance, for comparison with those maximum values.
