Negative power factor readings on SF6 CB

[OffTap2020]

Recently on our 72K Dead Tank( Alstom) SF6 CB's, we have been getting a rash of negative readings. We perform GST, GST (guard) and UST tests.
Some of our tests are coming back negative Pf, and negative watts. This has happened a couple of times in the past, and when tested a year later, the readings were normal.

Now today, we tested a particular CB, and on pole 5-6 we received 5.00 Pf. Our normal is (.08 to .90) This has happened once before, 2 years ago on another similar breaker. We gassed down, removed the end cover and inspected. No moisture, no contaminate. Nothing. Reinstalled end, gassed back up. readings became normal.

The negative watts and Pf is the one that confuses me the most though.

Any ideas or similar findings?

OT

 

[electricpete]

I recall Doble published about this.
Here is the first page of an article:

http://www.scribd.com/doc/61491351/Longs-Negative-Watts-1

That first page doesn't tell much. If you have a Doble subscription, you can go there and download the whole reference (there are probably more on the same subject)

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(2B)+(2B)' ?

 

[OffTap2020]

Thank you for the information.

OT