I have connected 04nos. earthings to a transformer through
04nos. earthing pits seperately. 02nos. earthings are
connected to T/F body, and 02nos. earthings are connected to
T/F neutral.T/F capacity is 2000KVA, 11KV/415V. But after
completing of 02 years successful operation ,we are
facing following problems-

1. CT/PT occured blast one time
2. HT cable box occured blast two times
3. One body earthing strip and one neutral earthing strip of
transformer are overlapping at some places. Whenever these
two strips are pressed at overlapped points, they made spark.

What is the reason of spark?

Please explain the reason & rectification of above problems

Answer Posted / siva kumar

because of improper earthing the transformer neutral voltage may raise to abnormal level and may cause failure of CT/PT sets.
The star point you made on secondaries of CT, should be made at the equipement only and connected to earth to avoid transfer potential.
If you have not integrated your earth pits,
connect all the four earth pits with 50X8 GI flat.
now check earth pit resistance is with in limits.

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