High Voltage CLEARANCE

[electpower]

Please have a look at the attachment. The Red circle shows the three phase connection of Isolated phase bus bar to the generator .The rated voltage of the generator is 21kv, Which means the Um value is 24kv, from IEC the clearance is 220mm, if choose a lightning impulse voltage of 125kV.

Say i choose to have a clearance of 220mm in the red circle area and a higher clearance value say 270mm in the blue circle area.
What are the weak points in the above configuration.Is there any disavantage in having such configuration, with different clearance along the Isolated phase busbars.
What are the problems associated with testing of such configurations?
Please suggest.

 

[jghrist]

It would be pretty difficult to design an installation where all clearances equal the minimum allowable. If there is a surge that exceeds the 125 kV withstand, the flashover will occur in the red area, not the blue area. Except for an impulse flashover test, there should be no effect on testing.

 

[electpower]

Thank u for the reply.
I have a clearance of 125kV in the area near the generator and clearance of 145kv away from generator.

Now if i have a surge, higher than 125 kV then it would strike the area near the generator, this is pretty clear.

However say if i have a clearance of 125kV through out, that is near the generator and far away from the generator, then wat would happen if the configuration faces a surge more than 125kV?

 

[jghrist]

However say if i have a clearance of 125kV through out, that is near the generator and far away from the generator, then wat would happen if the configuration faces a surge more than 125kV?

Then you would not be able to predict where the flashover would occur.