Answer / nizam salih

A pole drop test can be done when the generator is in
standstill condition. Provide a ac voltage of 230V to the
rotor terminals of the salient pole machine and measure the
voltage drop in each pole. At least 5A should flow through
the rotor poles. A small current will not provide good
results. Once the voltage drops are recorded calculate the
drop index as follows.
Index = (max. value - min. value)/avearge value *100 %
An index value of less than 5% reprsents the poles are
good.
This is the usual annual test that we carry out in our
hydro generators.
Nizam Salih, Electrical Engineer, Sri Lanka.

In our factory so many iron pillors are exists for supporting the shed/Hangar. If do more no of earthings at one piller instead of doing more earth pits in many locations and running earth strip around the hanger, I can save the money. Please suggest this method is acceptable as per Is specifications though the Earth resitance of the farthest piller is with in the limits as per IS specifications.

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