Failures of switches feeding transformers. 2

[edko]

Simultaneous electrical faults at three separate load interrupter (LI) switches at two separate substations.Voltage levels are 13.2KV -480V. They are high resistance grounded.. About 22 seconds later two other LI’s faulted at same substation and opened the upstream feeder breaker. Four switches were in disrepair. The weather was damp . These switches have been replaced before. Can an arcing ground fault cause this?

 

[rbulsara]

Yes, it can.
Time to review the whole set up.

Rafiq Bulsara

http://www.srengineersct.com

 

[Zogzog]

My money is on PD leading to a flashover with the damp weather. What type of maintenence gets done on these switches? Any PD monitoring? Corona scanning? Cleaning?

 

[racobb]

Especially depending on the environment...ie, dust, ash, chemicals from the site that might cause contamination.

Alan

 

[dpc]

With the HRG, a line-to-ground fault will put full phase-to-phase voltage to ground on the other phases until the fault is cleared. This additional voltage stress could have pushed the insulation over the edge. If the grounding resistor in the HRG kit is sized improperly, voltages can go much higher than that due to repetitive restrike.

 

[slavag]

Yep.
Dave Star!!!

 

[dpc]

But... maybe you were referring to HRG on the 480 V side? HRG on the 13.2 kV side would be unusual, at least in the US.

Lightning in the area?