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UV rated wire in outdoor installs

    Home forums/topic UV rated wire in outdoor installs

    Home › Forums › Transformer Rated Metering › UV rated wire in outdoor installs

    Post topics and questions about transformer rated metering.

    Tagged: Accuracy errors, CT, Instrument Transformers, PT, THHN, THHW, UV, VT, Wiring, XHHW

    • This topic has 0 replies, 1 voice, and was last updated 4 years, 7 months ago by Jason ChristoffJason Christoff.
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    • February 21, 2019 at 2:13 pm #8416
      Jason ChristoffJason Christoff
      Moderator

      Who is using UV rated wire for the secondary wiring of CTs/VTs where the instrument transformers are exposed to the elements?

      Minnesota Power has seen a number of issues with open circuited CTs, overburdened CTs, or missing potentials on meters where standard THHN or THHW wire was used. After 5-10 years in the field the insulation rots off and the copper disintegrates completely.

      In response to this we have started using XHHW. After 8-10 years of being in the field most installs still look like brand new. The only down side to using this is a #12 XHHW wire is slightly thicker than a #10 THHN wire. On a 9S install where we use #12 for voltages and #10 for currents we had to upside to 1.25 inch conduit instead of our usual 1 inch because it got too tight to pull through.

      MP’s standards call for #12 wire for voltage circuits and a minimum of #10 wire on CT secondary circuits. We also require all stranded wire, no solid core wire.

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