Answer / k.bhaskar

I think your neutral earth pits resistance is not
good,ensure each earth pit resistance with out grid.The
reason for sparking may be body earth is good and some
potential is there in the neutral path.

Second ensure transformer core channel to earth connection
(inside).Measure the winding resistance and unbalance load
distribution may also cause developing voltage in Neutral.

Answer / ullas

the answer follows.
1. ct/pt unit blast doesn't relate with the problem. it may
due to its poor quality , or some other reasons.
2. ht cable end box blast can be occured in so many ways.
may be due to rain water entered in to the end box leading
to short circuit the phases.
or due to poor quality,etc maybe the reason.
you can do one thing.
please disconnect the earthing of ht cable armour either at
transformer side or at the double pole structure.
3. this sparking indicated that your transformer neutral is
no longer maintains zero potential.
so please first measure the voltage of neutral.
this is done by inserting a spike five meters from the
transformer and take this terminal as earth terminal of
zero potential. and between this terminal and transformer
neutral measure the voltage developed.
if it is indicating a sufficient voltage, then it is true
that your neutral is shifted from its zero position.
if there is any fuse used in the neutral circuit, change
it in to a link.
check the whole circuit for any abnormal conditions.

Answer / santosh kawade

Please contact me Santosh 9224 69 3116,

Probably site inspection require to sortout your problem.

Answer / elangeswaran

pl check the type of load connected and if the secondary is
feeding a system of two sources with a buscoupler(three
pole) and neutral interconnected bus ultimatly neutral
voltage is above allowable level.

Answer / 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.

If single phase having 220v so why 3phase is440v.

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