Raptor
62
Ground grid
This template permits testing the integrity of the grids and
earth taps within a sub-station or power plant.
It is very important to regularly check the integrity of the
ground grid, and above all, of the connections from any
earthed element, as the buried part may have corroded
and this is impossible to detect unless it is done by injecting
current of the highest possible value, so that this
deterioration can really be detected. Being certain of the
correct integrity of the ground/earth system is essential, as if
one of these connections has deteriorated and an earth
fault occurs, it may simply blow just like a fuse would, which
may cause considerable damage to the protected
equipment.
Template configuration:
The template is configured as follows:
• Generator: Pass-through turn
• Time display: As timer in seconds (8 s, maximum length of high current
injection)
• V1in input secondary voltage meter in V. Auto Mode (voltage drop between
the points selected).
Connections:
Connect the pass-through turn(s) to the earth taps selected, where the current injection
will be carried out. In general, one earth tap must be selected as reference and another
as return. For example, the earth tap of the transformer and that of the circuit breaker.
The currents required for this test do not have to be very high, but the cables used must
be long enough to take the current to points that are relatively far away.
The cable cross-section chosen will have to be about 40 or 50 mm, winding 10 turns in
the equipment (C15 configuration at least will always be necessary for this type of tests),
for example, to reach significant distances of around 20 or 25 meters between test
points. Use quite a short cable to wind the turns and connect supplementary cable to
their outputs to reach the required distance.
Place the equipment close to one of the earth taps and extend only one of the ends,
above all the voltage measurement cable.
Connect the tips of the test cable of voltage measurement input V1*, in the tested earth
taps. The polarity does not matter.
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