Power Factor testing is least effective on which of the following?

[AlexT90]

Power Factor testing is least effective on which of the following? My Answer: MV Cable. I challenge this question, can anyone please elaborate?

[Kbryant777]

MV cable is the wrong answer because when you Tan Delta a cable it is basically another way of calculating power factor.

[veracon0700]

MV cable is the wrong answer because when you Tan Delta a cable it is basically another way of calculating power factor.

Agreed. Dry-type transformer is the best possible answer since you are essentially measuring the power factor of the air and there are too many variables that could have an effect on your readings.

[Kbryant777]

And until recently Doble didn't have Dry Type transformer as an option when doing power factor. Now with the use of a tip up test it is a more viable test.

[baldscreen]

Power Factor testing is least effective on which of the following? My Answer: MV Cable. I challenge this question, can anyone please elaborate?

You didn't list the possible answers for the test question. However, my vote would be for eliminating the test on SF6 breakers. Manufacturers don't recommend them or provide any acceptable values. I haven't seen any SF6 breakers with tapped bushings. They have always been hollow gas filled.

This test makes much more sense for oil-fill circuit breakers that did have tapped bushings.

[ElectricalTestTech]

You didn't list the possible answers for the test question. However, my vote would be for eliminating the test on SF6 breakers. Manufacturers don't recommend them or provide any acceptable values. I haven't seen any SF6 breakers with tapped bushings. They have always been hollow gas filled.

This test makes much more sense for oil-fill circuit breakers that did have tapped bushings.

I would have to disagree with this statement. The purpose of power factoring in SF6 breakers is to detect the presence of contamination and/or deterioration of the breaker’s insulating system. A power factor test is not just for tapped bushings. There are other tests like hot collar tests that can test a bushing without taps. And even if you place the HV lead on the lug pad of the bushing and connect the ground to the tank (assuming its a dead tank breaker), perform an open breaker GST test, you are still stressing the bushing, internal support insulator, and the SF6 gas.

I would strongly recommend that you read some of the articles about power factoring on TestGuy. They are extremely helpful and may give you a better understanding about power factoring.

https://testguy.net/content/250-3-Basic-Modes-of-Power-Factor-Testing

Good luck!

[madsenate]

Power Factor testing is least effective on which of the following? My Answer: MV Cable. I challenge this question, can anyone please elaborate?

In reading the various posts on this thread, I'd say you all could be right...or wrong. It depends on the selection of test answers given. Sort of a "lesser of 4 evils" type question. They could list 4 things that all have valid PF results possible, but which one is PF testing LEAST effective on.

I could PF test my desk here and get some result....but what would it mean and am I wasting my time?

I f*cking hate those questions........who cares if PF testing a 15kVA xfmr is a waste of time, the f-ing job specs said to do it, so we're doing it!

[testguy]

In reading the various posts on this thread, I'd say you all could be right...or wrong. It depends on the selection of test answers given. Sort of a "lesser of 4 evils" type question. They could list 4 things that all have valid PF results possible, but which one is PF testing LEAST effective on.

Spot on with this. Many NETA questions are "best answer" type. Original options for this question were:

A. Dry type transformer
B. Oil filled transformer
C. MV Cable
D. OCB
E. Voltage regulator

[nickhaughton]

You didn't list the possible answers for the test question. However, my vote would be for eliminating the test on SF6 breakers. Manufacturers don't recommend them or provide any acceptable values. I haven't seen any SF6 breakers with tapped bushings. They have always been hollow gas filled.

This test makes much more sense for oil-fill circuit breakers that did have tapped bushings.

yep

[dadrjka16]

Agreed. Dry-type transformer is the best possible answer since you are essentially measuring the power factor of the air and there are too many variables that could have an effect on your readings.
I had selected the option of MV cable as well, only because lately in specs I have been seeing more and more the requirement to record the power factor of a dry type XFMR larger than 500KVA.