Loop Impedance Testing

For any installed circuit, the earth loop impedance must be sufficiently low to ensure that protective devices operate in the event of a fault.

The Video

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Loop Impedance / Earth Loop Impedance

Earth loop impedance consists of the external impedance (as measured at the origin or incoming supply) plus the impedance of the particular circuit wiring.

This test is one of the last tests done, and by this stage earlier testing will already have provided a value for this - however it is still useful to confirm the loop impedance once the circuit has been energised.

Impedance can also be measured between line and neutral to estimate the current which will flow in the event of a line-neutral fault.