38 39
resistance of the opposite line, and then divided by2.
Ground resistance value of other two reference ground bodies are:
RB=R1-RA RC=R3-RA
X On-site Application
1 Application of Power System
(1).Measurement of the power line tower ground resistance
Generally, the power line tower ground form into multi-point ground system
and clamp on the ground down lead by UNIT series clamp meter , the ground
resistance value of the branch circuit could be measured.
(2).Measurement of transformer neutral point ground resistance
In measuring the transformer neutral point ground resistance, if data
fluctuates greatly , power off and test.
There are two circumstances for the transformer neutral point ground: form
into multi-point ground system if repetitive ground exists; single point ground
measurement if no repetitive ground.
In measurement, if clamp meter display L 0.01 it is possible that more
than 2 ground down leads of the same tower or transformer are connected
underground. It is need to maintain only one ground down lead, and unfasten
others.
(3).Application of power plant and substation
UNIT series clamp meter can test the loop contact and connect condition and
can measure the connection between equipment in the station with the ground
net by a test line. The ground resistance could be measured as the single
point ground.
2 Application of Telecommunication System
(1).Ground resistance measurement of the floor computer room
The computer room of the telecommunication system is always established
on the upper floor of building, difficult to measure by tramegger. While it is
quite easy for UNIT series clamp meter to test, just connecting a test line with
fire hydrant and the ground polarity being measured (each computer room is
equipped with fire hydrant) and measuring the test line with clamp meter.
Clamp resistance value=computer room ground resistance +test line
UT276A/278A OPERATING MANUALUT276A/278A OPERATING MANUAL
To Next Page
Loading...
