Ground Loop or Couterpoise Required for Pad Mounted Tran

Status
Not open for further replies.
E

eeee

Senior Member
My colleague suggested that I need a ground loop or counterpoise installed for my pad mounted 3phase, 300KVA, Delta-Wye connected, 208/120 volts, 12,460 volts primary transformer. I have a ground rod installed now which obviously goes in to the ground (I believe it is 10feet)and this is what I have seen done by a previous contractor's design.

I assume I must tie it in with the facility ground for the building located nearby if I use a ground loop or counterpoise?

Can I go without the ground loopo or counterpoise is question 1?

Do I have to tie it in with the facility ground for the building if I must use a ground loop or counterpoise is question 2?
 
Re: Ground Loop or Couterpoise Required for Pad Mounted Tran

What kind of primary cable are you installing, and does it have a ground with it? You would need to drive a ground rod at the transformer, at a minimum, but if the cable is concentric neutral or has a separate ground wire pulled in a multiply grounded system, it is grounded at so many locations that a ground loop will not materially affect the ground impedance.

Many of these ideas come from designers who aren't well versed in NESC type systems, and add significant costs to projects. If you have a typical grounded wye primary system, you shouldn't need a ground loop or counterpoise.

Jim T
 
Re: Ground Loop or Couterpoise Required for Pad Mounted Tran

I am using XLP, 133% concentric neutral primary cable. The primary is a Wye, but I am configuring the pad mounted transformer for a Delta primary and the secondary is a WYE.

I am concerned that you indicate I must have a typical primary Wye. I have a Wye comming in, but am installing a delta primary tranformer and configuring the transformer for a delta. I am now worried that I just nullified your presupposition that I have a Wye primary.
 
Re: Ground Loop or Couterpoise Required for Pad Mounted Tran

Don't worry, the delta transformer connection won't change my belief that you do not need a loop or counterpoise. You still have a grounded wye primary system regardless of how an individual transformer is connected. If the concentric neutral is grounded often, as is the usual case, your loop won't help. Just drive a ground rod, and connect the tank ground, the concentric neutrals, and the low side neutral together and tie to the rod. If you have elbow arresters in your transformer enclosure, you would want a second rod for them.
 
Re: Ground Loop or Couterpoise Required for Pad Mounted Tran

I agree with Jim's reply. We install these systems all the time and do exactly what he mentioned. When we pour our pads, we drive a rod in the knockout and ground our primary neutral, secondary neutral bushing, cable shields and tank pad to the rod.
 
Status
Not open for further replies.
Top