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Chapter 4 Measurement Procedure
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(5) Influence of earth voltage
Due to the presence of leakage current from
electrical equipment connected to the earthing
body or of earth current, a voltage may exist at
the earthing body. If the voltage is less than
about 10 V, it will normally not affect the
earthing resistance measurement. However, if
the earth voltage is distorted, it may cause
measurement errors even at lower voltage
levels. For this reason, if an earth voltage of
more than about 5 V is detected, other
electrical equipment should be switched off or
the equipment should be disconnected to
eliminate the influence of earth voltage on the
measurement.
During simplified measurement, harmonic
leakage current in the ground line can cause
the galvanometer to fluctuate. In such a case,
change the setting of the 2/3 pole measurement
selector (
TERMINALS) from "2a"to"2b" (from
"
3a"to"3b" for normal measurement). This
may allow stable measurement.
If earth voltage is high, the insulation of the
electrical path or electrical equipment may
have deteriorated. Check the insulation and
perform a leakage current test.
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