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Dobble test on bushing (330kv)

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    Dobble test on bushing (330kv)

    Hello guys,
    I performed C1 test on the HV 330kv bushings on auto transformer and the results for the capacitance were the same as that of the nameplate but my power factor values were 5.671, 3.245, 5.743 (ie A,B,C Phases).these values are higher than benchmark values which were all below 1 ( ie 0 45, 0.54, 0.62)
    Guys can these bushings be used back in service?
    Also is there a way to do to bring the power factor values to less than 1?
    Waiting for response
    Thanks
    Last edited by samkay; April 8, 2020 at 09:28 AM.

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    Quote Originally Posted by samkay View Post
    Hello guys,
    I performed test on the HV 330kv bushings on auto transformer and the results for the capacitance were the same as that of the nameplate but my power factor values were 5.671, 3.245, 5.743 (ie A,B,C Phases).these values are higher than benchmark values which were all below 1 ( ie 0 45, 0.54, 0.62)
    Guys can these bushings be used back in service?
    Also is there a way to do to bring the power factor values to less than 1?
    Waiting for response
    Thanks
    Some generic questions:
    C1 or C2 tests?
    Clean?
    How and in what condition were the benchmarks obtained? (attached to xfmr, floating, weather, etc)
    What was your test setup/procedure? Does it match the previous test proceedure?
    What was the year span in between tests?
    Are the watts losses negative?
    Did you test one bushing at a time? Meaning did you only remove 1 C2 shorting tap at a time and replace the non-tested?

    Proper grounding is huge. You can test grounding by removing that red jumper you shouldn't be using and attempting to attach it to an independent ground. If it gives an error, chances are one or both of your selected grounds are faulty.

    Also note: if your Doble PF unit is under lease from them, you get their customer support. They have helpful info on characteristics of specific components due to their database.

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