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Negative power factor results on sf6 breaker

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  1. DLWood is offline Junior Member Pro Subscriber
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    Negative power factor results on sf6 breaker

    Testing a 72.5kv sf6 breaker, getting results like -.001 and -.002. Suspect may be due to tracking on dirty surface, in the process of cleaning but does anybody have any additional insight to this situation?

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  3. rofo42 is offline Seasoned Member
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    Quote Originally Posted by DLWood View Post
    Testing a 72.5kv sf6 breaker, getting results like -.001 and -.002. Suspect may be due to tracking on dirty surface, in the process of cleaning but does anybody have any additional insight to this situation?
    More than likely it is dirty surfaces causing a resistive current path.

    Things to also try, only use the length of ground cable and red/blue cables that are necessary and don’t have them laying on the ground. Also, try different ground locations and ensure you have single point grounding.

    It can also be a hook or sensing lead location issue. Simply try moving the hook/red/blue leads to different spots on the breaker.

    Be careful with your choice of cleaner. I much prefer to try a clean dry rag first. If it’s humid and overcast, you might need to clean and try again tomorrow.

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    Quote Originally Posted by DLWood View Post
    Testing a 72.5kv sf6 breaker, getting results like -.001 and -.002. Suspect may be due to tracking on dirty surface, in the process of cleaning but does anybody have any additional insight to this situation?
    Definitely would look into any grounding issues with either the set or breaker.

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  7. rofo42 is offline Seasoned Member
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    Quote Originally Posted by DLWood View Post
    Testing a 72.5kv sf6 breaker, getting results like -.001 and -.002. Suspect may be due to tracking on dirty surface, in the process of cleaning but does anybody have any additional insight to this situation?
    Something I just thought of but have never tried is using hot collars on the base porcelain and attaching them to the guard ring on the high voltage hook. This should, in theory, guard out any resistive losses you are having across the bushing. Again, never tried it but know that it is something Doble used to recommend trying.

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  9. pallen is offline Junior Member Pro Subscriber
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    [QUOTE=DLWood;15828]Testing a 72.5kv sf6 breaker, getting results like -.001 and -.002. Suspect may be due to tracking on dirty surface, in the process of cleaning but does anybody have any additional insight to this situation?[/QUOTI

    I came across this Megger Power Factor seminar on youtube, It's in-depth and covers negative Power Factor results as well as DFR NBDRF etc...

    Results.https://youtu.be/zFOzaa-WE_0

    Hope it Helps.

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    Negative results

    For all test it is recommended to be completely isolated from any external bus or cables. Tests 1-6 do not require the use of a low voltage lead as the current returns to the test set by the ground calbe. Never place a jumper from the ground to the ground stud on the test instrument. If you are using software provided by Doble it is not uncommon to have negative test results for tests 7-9 (UST). Consult the limits for the type of breaker you are testing and if a Doble client you can benchmark your breaker against their database for that type of breaker. You also can contact Doble for assitance with any concerns. As mentioned in prior emails a negative power factor is usually due to a resistive path to ground.

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