-33-
mission piper of tanker: R=R
T
-R
L
NOTE: R
T
is the resistance meter measured; R
L
is the resistance
of testing line.
Ⅺ
. Matters need attention when measuring grounding re-
sistance
1. Users may sometimes compare ETCR with voltage-current
method of traditional, and a big different appeal; to solve the situa-
tion, users should pay attention to the problem mention below.
(1).whether the grounding body which being measured is dis-
connect with earth system when use traditional way like vol-
tage-current method. If not, then the value is a parallel result of all
the grounding body.
It is useless to measure the parallel result of all the grounding
body, because the aim why we measure the grounding resistance
is compare it with a allowable value which is stipulated by relevant
standards, to justice whether the grounding resistance is up to
standard.
For example: the grounding resistance allowable value stipu-
lated in GB50061-
97 ―Design standard of overhead power line with
the voltage of 66KV and below‖ is especially for ―each tower‖. The
specification of the standard says that: ―grounding resistance of
each towers, is a value when the grounding body and the groun-
ding line is separated. If the grounding body doesn’t separate with
grounding line, then the grounding resistance be measured is the
parallel result of several tower.‖
This standard is very specific.
Like what have mention before, the value measured by ETCR
series clamp meter is the grounding resistance of each branch, if
the connection of grounding line is good, it is the grounding resis-
tance of one grounding body.
Obviously, in this condition, compare the result which meas-
ured by traditional voltage-current method with the result meas-
