1. OBJECTIVE
This Method of Statement is meant to describe in
generality the Earth Grid Test process; which describes its general setup and
how the test is carried out.
2. SAFETY
All personnel should
continuously and consciously observe his work area for any potentials danger
and take adequate measures.
In general:
a)
All personnel should wear Personal Protective Equipments
suitable for the work and work area (e.g helmet, safety boots, goggles, glove,
etc)
b)
If working in live station, ensure that isolation is done and
Permit To Work is issued. If possible, ensure no REMOTE operation is allowable
such as put the section into LOCAL.
c)
Ensure that the working area is only at the permitted area.
d) Earth/ground test
equipment
3.
GENERAL EARTH RESISTANCE TEST
a.
General Setup
For this Method of Statement, we use KYORITSU Digital
Earth Resistance Tester as our test equipment.
Setup the equipment as shown in Figure 1;
-
Stick the auxiliary spikes P and C into the ground deeply.
They should be aligned at an interval of 5-10mtr from the earthed equipment
under test. Connect the green wire to the earthed equipment under test, the
yellow wire to auxiliary earth spike P and the red wire to the auxiliary earth
spike C from terminals E, P and C of the instrument in order.
-
Set the range switch to the EARTH VOLTAGE position in the
condition of
1. Earth voltage will be
indicated on the display. Make sure that the voltage is 10V or less. When the
display reads more than 10V, it may result in excessive errors in the earth
resistance measurement. To avoid this, make measurement after reducing the voltage
by turning of the power supply of the equipment under test etc.
b.
Test
Process
Set
the range switch to 20Ω position and press the push button (PRESS TO START).
LED remaining laminated during the testing. Let the device for a few second and
the measured value will appear on the LCD Display.
If
the auxiliary earth resistance of auxiliary earth spike C is too high to make
measurement, the display reads ‘….’ Recheck the connection of the test leads
and the earth resistance of auxiliary spikes.
c.
Test
Acceptance Value
-
Resistance value for earth rod -
less than 10Ω
- Resistance value for earth rod with
cooper tape - less than 1Ω
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