- the insulation resistance must be measured with amegohmmeter (external or with standalone source) at
a minimum voltage of 500 VDC
- the assembly being tested must be turned off and there must be no receiver devices connected
- all the breaking devices must be in position i (on)
- the voltage is applied between each circuit and the exposed conductive part
- it is possible to link all the poles: phases and neutral,except in tnC layout in which the pen conductor is considered to be linked to the exposed conductive part
of the assembly.Devices (measurement windings, instruments) which would not withstand the test voltage must have their supply terminals short-circuited.
the measurement conditions can influence the results obtained. measurements should not be carried out temperatures below dewpoint (condensation will
dampen the surfaces).
the insulation resistance decreases with the temperature.if repeated measurements have to be taken,the environmental conditions must be recorded. the period for which the voltage is applied also has a major influence, and measurement can be considered to consist of three sequences. at the start of measurement, the device charges the capacitor which represents the installation in relation to earth and the leakage current is at its highest.
LEGRAND POWER GUIDE
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