Earth grid testing

[sivajith]

Can we perform earth grid testing for a substation while it is energized. I have come across some test units that injects current at different frequencies other than 50Hz for this purpose?

 

[7anoter4]

In my opinion, you can, but you have to follow the safety precaution up, as per IEEE 81/1883 [for instance]:
5. Safety Precautions While Making Ground Tests 5.1 Station Ground Tests:
"It should be strongly impressed on all test personnel that a lethal potential can exist between the station ground and a remote ground if a power-system fault involving the station ground occurs while ground tests are being made." and further:
"For higher ground impedance or greater fault currents, the rise of station-ground voltage may exceed 10 kV.”
Instead of 50/60 Hz you could use 500 Hz tester. See :

http://cindulkar.tripod.com/lab12.pdf