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4. INSULATION RESISTANCE MEASUREMENTS
a). Measurements at 200M
Ω
/250V. This is the
voltage used for the majority of insulation resistance
tests on normal installation requirement. To
measure insulation resistance, press the test button
to power on the tester. The LCD will display the
insulation resistance. Section VII indicates that
subdivision of large installations might be necessary
because of the large number of parallel insulation
resistance. In such a case, an installation may be
divided into sections, each being separately tested.
Each section must have not less than fifty outlets,
an outlet being a switch, socket, lighting point etc. A
switched socket counts as one outlet. The minimum
acceptable insulation resistance is 1M
Ω
. For a
large installation, the capacitance of the insulation
will be high, and it will take longer for it to become
charged by the direct testing voltage. Care must be
taken not to take a reading until there is a steady
reading, indicating that the charging process is
complete.
Note:
The charge stored in the insulation will be
