This Q & A of the Day, concerning Ze external loop impedance testing, is answered by the NICEIC in this series where our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area:

Answer: Ze can be measured using a proprietary instrument and the correct test leads - to do this the supply cable must be LIVE. As live measurement is being undertaken, appropriate safety precautions shall also be taken to avoid danger.
Alternatively, a nominal value of Ze can be obtained by enquiry from the local electricity company.
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