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ured by ETCR series clamp meter doesn’t make any sense. Be-
cause what have been measured is different, the big different of
the result is make sense.
(2).The grounding resistance measured by ETCR series clamp
meter is comprehensive resistance of grounding branch. It in-
cludes the contact resistance of the public grounding line of this
branch, lead line resistance and grounding body resistance. Under
the condition of disconnect with grounding line, measured by vol-
tage-current, the value is just for grounding resistance.
Obviously, the former one is larger than the latter one. The
contact resistance of branch and public grounding line is what
makes them different.
What need to specify is the grounding resistance should in-
clude the resistance of lead line which is stipulated by the national
standard. Terminology in DL/T621-1997 ―The grounding of AC
electric‖ stipulated as: the grounding resistance of grounding de-
vice is the total of the resistance to the ground of grounding pole or
natural grounding electrodes and the resistance of grounding line.‖
This kind of stipulate is specific. Because the resistance of lead
line and the grounding resistance of grounding body is equal for
lightning protection.
2. Selection of measurement point
In some grounding system, like the picture show below, should
chose a correct point for measurement, or will get different result
When measuring at A point, the branch doesn’t form a circuit,
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