46 47
Connect oil stopper with the oil-filling machine by a test line and measure the
reading RT by clamp meter, then calculate:
Oil-filling machine oil hose connection resistance: R=RT-RL
Of which, RT is the resistance value measured by clamp meter, and RC is the
test line resistance.
XI Notes about Ground Resistance Measurement
1 If users find great difference after conducting comparative test between the
series product and traditional voltage/current method, please pay attention to the
following notes:
(1).Find if tripping in using the traditional voltage and current method (if
disconnect the ground body being measured from the ground system). If no
tripping, the measured ground resistance value is the parallel value of ground
resistance of all ground bodies.
It is meaningless to measure the parallel value of ground resistance of all
ground bodies, as our purpose of measuring ground resistance is to compare
it with an allowable value stipulated by relevant standard, judging whether the
ground resistance is qualified.
For instance: the ground resistance allowable value stipulated in the GB50061-97
Code for Design of 66kV or Under Overhead Electrical Power T ransmission Line
is designed for Each Tower. It is clearly stated in the standard that: ground
resistance of each tower refers to the resistance value measured after
disconnecting the electric connection of ground wire from ground body. If the
ground body have not been disconnected electric connection of ground wire from
ground body, the ground resistance measured shall be the ground resistance of
multi-towers in parallel.
The stipulation is clearly stated.
As mentioned above, measured result of the series clamp meter is the ground
resistance of each branch circuit, under the condition of good conductivity of the
ground wire; it is the ground resistance of single ground body .
It is evident that under the circumstance, it is no comparability of the
measurement results tested by the traditional voltage current method and the
series clamp meter . As the object being measure is different, the evident
difference between measurement results is reasonable.
(2).The ground resistance value measured by the series clamp meter is the
UT276A/278A OPERATING MANUALUT276A/278A OPERATING MANUAL
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