BS7671 (16TH EDITION WIRING REGULATIONS)
REQUIREMENTS
Regulation 713-11 of BS7671 specifies that the
resistance of earth electrodes must be measured. The
accompanying Guidance Notes describe a method of
test that is very similar to the Fall-of-Potential method.
If the maximum deviation from the average of the three
readings is better than 5% then the average can be
taken as the earth electrode resistance. If the deviation
exceeds 5% then the current spike should be moved
further away from the electrodes and the tests
repeated.
Fig.15 Test spike positions for BS7671 testing
Other Methods
There are other methods of earth electrode testing
among which are the Four Potential, Intersecting Curves
and Star Delta methods. Megger Limited have produced
a book entitled ‘A Simple Guide to Earth Testing’ (Part
Number 6171-230) which explains all these test
methods and gives other helpful information about
earth testing. It is available from the instrument
manufacturer or one of their approved distributors.
22
MEASURING TECHNIQUES Testing Earth Electrodes
6m 6m
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Summary of Contents for DET5/4D
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