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Tan Delta versus Partial Discharge testing on cables

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    Tan Delta versus Partial Discharge testing on cables

    Thoughts on this? What is the preferred test for all of you, and why?






    www.taifaengineering.com

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    Quote Originally Posted by TaifaEngineering View Post
    Thoughts on this? What is the preferred test for all of you, and why?






    www.taifaengineering.com
    It all depends on the application. In general I feel that the Tan Delta is the better test but it is more invasive the cable must be de-energized and made safe. The Partial Discharge testing if they have the hardware installed can be done live.

    In general for a site that has infrequent shutdowns Partial Discharge would be the way to go and it can provide information on problem cables that you can then check with Tan Delta during a shutdown.

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    Quote Originally Posted by Nick1234 View Post
    It all depends on the application. In general I feel that the Tan Delta is the better test but it is more invasive the cable must be de-energized and made safe. The Partial Discharge testing if they have the hardware installed can be done live.

    In general for a site that has infrequent shutdowns Partial Discharge would be the way to go and it can provide information on problem cables that you can then check with Tan Delta during a shutdown.
    My last company recommended performing Online PD annually, and every 5 years performing Tan-Delta or Offline Partial Discharge since OLPD doesn't detect minor electrical treeing, while the offline test can.

    I believe the overall difference lies in the cost and safety placed on the customer to work around. Tan-delta is cheaper (I have determined failure in a cable within 3 months with TD), but Offline Partial Discharge is much more accurate, and Online Partial Discharge is more convenient to continued operations.

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    Quote Originally Posted by TaifaEngineering View Post
    Thoughts on this? What is the preferred test for all of you, and why?
    www.taifaengineering.com
    Offline PD is the most accurate if you are going to take the cable down but is really specialized and expensive. Tan Delta combined with VLF will give you a good baseline for comparison in the future and is much cheaper. Online PD is a good non-distructive test, but like an infrared scan its only useful for monitoring, not a replacement for offline maintenance.

    From NETA World Spring 2017: Tan delta tests the health of the insulation as an average value of the length of the cable, and therefore, small sections with significant defects cannot be detected. Partial discharge detects these small defects but cannot detect aging effects (like water trees) until they result in discharge. Thus, these two tests are complementary, and it is advisable to do both at the commissioning of any cable.

    https://www.eatechnology.com/america...17_FlowONE.pdf

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