Recloser switching overvoltages

[radug]

Hello,

I am reading insulation coordination standards and references and I have read that with three-phase reclosing the switching overvoltages are quite higher than with single-phase reclosing.
Can anybody explain the fundamentals of this? I have tried looking at high voltage equipment manufacturer websites and have been unable to find any theoretical explanation for this. And I have not found any information about how three-phase reclosing and single-phase reclosing work.
It is for a 230 kV transmission line.


Thanks.

 

[karalahana]

I think this has to do with the fact that in three phase reclosing it is impossible practically to get simulatenaous opening of three phase , so one of them will be the first to open and when it is open the other two phase reactances will add some voltage to the trv of the first pole. here other phases will increase the voltage across the poles...

 

[m3ntosan]

Assuming it’s impossible to close the CB’s at both ends at the same time and knowing that circuit’s characteristics (like capacitance and inductance) and fault level may affect the over-voltage level, I would say it’s sensible to assume that whenever you’re switching in/out three phases instead of one you’ll end up with different values for fault level and line characteristics.
I would expect to have different over-voltage values for offloading and charging of the circuit with the offloading being more onerous.

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