Bus Bar differential & Transformer Energisation

[rajendrarohra1978]

Hi, We had Bus Bar Differential operated during Transformer Energisation ( 75MVA)
THe CT's are measruning input & output currents for Bus Differential
Has someone observed similiar issue. The Bus is healthy & also teh Transformer.

Thanks in advance

 

[Parchie]

@rajendrarohra1978,
We need more info. We can't possibly guess things out of the blue. What data do you have?

 

[thermionic1]

The first place to check is CT polarity and secondary wiring.

 

[cranky108]

I have seen this, and it was because of CT wiring/wrong polarity.
Really need more information, and what type of differential.

 

[waross]

I remember years ago studying the theory and operation of an electro-mechanical transformer differential protection relay.
First there was a CT ratio to compare the primary current with the secondary current.
This function was then biased to balance out errors caused by no ,oad losses.
Another feature balanced out load dependant losses.
I don't remember how inrush was accommodated, possibly with a time delay.
The point is, there is a lot going on when a transformer is energized.
If this was infrequent or a one time thing, the transformer energization current may have saturated a CT.



--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[edison123]

Reversed CT primary or secondary. Too low a bias.

Muthu

http://www.edison.co.in

 

[wcaseyharman]

Issues I’ve seen for misoperating differentials:
- loose/bad CT wire connection
- miswired
- transformer compensation not set right in microprocessor relay
- CT shorting terminal left in
-2nd ground in CT circuit
-test switch left open
There are certainly more but these have happened to me or my coworkers.