Results 1 to 6 of 6
  1. #1

    Default When do you use a floating nuetral, and what banks?

    Featured Sponsor

    Trying to read about it. Mainly for Y delta banks.

    i remember 480 banks, we would ground a leg, for in rush current.

    Having a floating nuetral on the primary of a y bank, where the common is just bonded together. Is there a reason to float it in some cases or a situation? Did you ever go to a property where they just bond the primary nuetral bushings, but they never give an answer why they want that done. And if you just bond and don't tap to ground, why do they tell you to do that?

    and I know when you have a Y delta primary step down, you ground the common til you have the doors closed. Then open the common for the ground.

  2. #2

    Default

    Y primary closed Delta banks we use a floating ground, I have seen the same banks built at other utility's with all 3 pots grounded down, but have also saw on same system 1 of the pots in the bank opened up ( fuse blown ) bad pot animal whatever and with the pots grounded down it become an open delta with 2 overloaded pots, until there is another problem or someone from the power company sees it, it stays that way, now on some Delta banks we will hang a 4th cutout to temporarily ground down the floating neutral due to Ferroresence, but that's a whole different story.

  3. #3

    Default Thanks LNF

    Just on your four wire and straight power delta secondary?

  4. #4

    Default Thanks LNF

    Just on your four wire and straight power delta secondary?

  5. #5

    Default

    Quote Originally Posted by bobbo View Post
    Trying to read about it. Mainly for Y delta banks.

    i remember 480 banks, we would ground a leg, for in rush current.

    Having a floating nuetral on the primary of a y bank, where the common is just bonded together. Is there a reason to float it in some cases or a situation? Did you ever go to a property where they just bond the primary nuetral bushings, but they never give an answer why they want that done. And if you just bond and don't tap to ground, why do they tell you to do that?

    and I know when you have a Y delta primary step down, you ground the common til you have the doors closed. Then open the common for the ground.
    Where I worked, there is a lot of 12kv with no neutral. Did a lot of 21kv cut-overs, and pulled a lot of neutral for that. In a few agricultural areas, they did cut-overs from 12-21kv thru auto banks, no neutrals. There are 2 cases where a floating neutral was used. 12kv cap banks is one, leave the 12kv units in place, float the neutral. The other was 3 pot 480 banks. If they were under 300kva, we would replace with a 3 phase 21kv trans. If over that, 135s or 167s, we floated the Wye. As I've stated many times before, you do not run a ground down the pole to earth to ground it. Because there is no return neutral, you have the potential to place primary voltage at ground level if someone cuts that ground.

  6. #6
    Join Date
    Dec 2010
    Location
    Ontario, Canada
    Posts
    1,012

    Default

    Featured Sponsorr

    the rule of thumb here is, wye -delta float the neutral. meaning wye primary delta secondary, float the primary neutral. requires cans with 2 insulated primary bushings. its not done here much anymore, most places have gone to building wye-wye banks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •