Can disconnect switch be used to energize transformer?

[QBplanner]

In the company I work, we used to have a case that in a weak system (138kV extising and 230kV ultimate) with fault level only 110MVA we plan to install two 120MVA auto transformers 230/138/25kV. I had a concern for transformer inrush current and teh impact to the distribution loads along the line. But our transformer expert mentioned that they can use disconnect switch to energize the transformer without causing inrush problems. I recall that Bpa (In North America) did some research to monitor the transformer residual flux when trying to close the CBs. However, I have no clues how the disconnect switches work on energizing transformers.

Could any transformer experts share some throughts of what will happen by using disconnect switch energizing transformers?

Thanks in Advance!

 

[RRaghunath]

The Air-break disconnecting switches I have come across are only 11kV and are used for transformer switching as well. These switches are manually operated but have a spring as part of the operating mechanism that makes the switch make its contacts with a snap action.
The motorised switches which operate slowly I have come across at higher voltages but these are not used for transformer energisation (pure disconnectors).
About closing repeatedly, I agree with you, jghrist.

 

[QBplanner]

jghrist :
thanks for your response. Do you have any recorded inrush currents when using disconnect switch picking up Trx at 100kV level.
I would like to see the differences between CB and disconnect switch when picking up Trx.
Thanks!
QB

 

[jghrist]

thanks for your response. Do you have any recorded inrush currents when using disconnect switch picking up Trx at 100kV level.
I would like to see the differences between CB and disconnect switch when picking up Trx.

I don't have any recorded inrush currents with a disconnect switch energization. I don't see any reason why this would affect the inrush, however. Maybe a slight pre-insertion resistor effect (from a short prestrike arc) to reduce inrush, but I wouldn't count on any reduction.