Page 240 - Electrical Safety of Low Voltage Systems

CHAPTER14

Testing the

Electrical Safety

Zeal without knowledge is fire without light.
thomas fuller (1608–1661)

14.1 Introduction
The parameters that ensure electrical safety in installations can, and
must, be tested to positively assure that the risk of electric shock is
below the limit deemed acceptable by the electrical design.
Some measurements must be carried out during the design phase
(e.g., soil resistivity test), in order to have objective input data, and for
others (e.g., earth resistance test) after the installation of the electrical
system, and prior to being put into service. This allows a comparison
between test results and the relevant design data, which must be in
possession of the verifier.
Electrical safety obtained due to the proper deployment of pro-
tective measures against direct and indirect contact tends to decrease
in time due to aging of the electrical system; therefore, cyclic testing,
together with preventive maintenance, are necessary to assess, and
eventually restore, the level of safety. Test procedures, of course, must
not endanger persons or damage the property, and must be carried
out with procedures and instruments in compliance with relevant
technical standards.

14.2 Soil Resistivity Measurement
As we already know, the resistivity of soils play a crucial role in deter-
mining the performance of ground electrodes, as it is a major factor in
influencing their resistance to earth. For this reason, prior to designing

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