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thread238-349003 - Negative Power Factor Readings on SF6 Circuit Breaker

thread238-349003 - Negative Power Factor Readings on SF6 Circuit Breaker

thread238-349003 - Negative Power Factor Readings on SF6 Circuit Breaker

There is a closed thread, 238-349003, with a bit of discussion on Negative Power (and Watts) readings on an SF6 breaker.
We recently had a brand new 345kV Gas breaker flash over internally upon initial energization. The system was from the remote end and approximately 4 minutes after energization, the remote end cleared the ~22kA fault.

When the breaker was initially commissioned, negative PF and Watts loss were noted. The manufacturer was contacted and we were told this test was not recognized in their field commissioning procedure. We had tested 9 identical GCB's and this was the only unit to exhibit the negative PF/Watts condition.

Of course the OEM will remove the entire pole unit and replace. I doubt we will ever get a real root cause.

The negative values were obtained in the Open, UST condition. A little research yielded that Negative or lower than normal power factor or watts loss that is obtained in either the GST guard or UST modes, can indicate resistive tracking to ground.

RE: thread238-349003 - Negative Power Factor Readings on SF6 Circuit Breaker

This type of negative PF is due to tracking over porcelain or other supporting insulators. Normally cleaning will restore the same.

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