The video depicts the Z line / loop impedances testing (with the 4-wire Kelvin method) procedure at the three phase main distribution board connection (applicable for any building for referencing measurements, whether for initial inspection or scheduled maintenance). The results of available short circuit currents and prospective fault currents are important part of selectivity and safety protection reporting. It should also be noted that the basic protection in the surroundings of any building represents its grounding and earthing. And for testing in such urban environments, on TN earthing systems, the 2-clamps measuring method is particularly suitable; three cases explained; at the main potential equalisation (MPE) point, at the grounding shaft (GS), and at the main protective earthed neutral (PEN) conductor.
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