Answer / p.v.subbaiah

Earth resistance can be measured with earth megger.There is
some values for the earth resistance.For 33kv s.s the earth
values should be less than 1 ohm.etc.
To control earth
resistance with in the limited range we have to monitor the
earth pits regularly.If the values are beyond the limit
then pour salt,coal and water.Then check the values.If your
sub-station is at dry area then you have to pour some
chemical called BITUMAN COMPOUND in the earth pits.Then
your earth values are safe.

Answer / meenakshi

i vud lyk to enhance mr.subbiah's answer...

for large power stations- 0.5 ohm
major power station - 1 ohm
small substation - 2 ohm
other cases - 8 ohm
controlling here means the measures 2 b taken to reduce the
earth resis value
- use no of earth electrodes in parrlel connection
- v can replace the existing electrode by a larger dia
electrode
- depth of pit can b icreased in order to get more moisture
n water content in the soil
-n the important method as mentioned by subbiah

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