Primary service grounding. If the customer purchases a primary load break switch, and xfmr. Located on 2 pads approx. 15? apart. The primary cable comes into the load break, then to the xfmr. Then into the existing facility switchboard, if you provide a ground mat at the two pads each connected to the associated equipment equipment (one ground ring connected to the xfmr., and one to the load break switch ground bus, when you run the primary cable from the switch to the xfmr. you would connect each ground at their terminations one at the xfmr ground, and one at the switch ground bus. My question is that if the utility wants their own ground mat and does not want to be tied into yours how do you accomplish this? Or is this only for secondary services??
Utility Primary Services
- Thread starter Mike01
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You can't separate the two. As you said the jumper between the switch and the transformer will create a bond between the two. This sounds like either a customer owned situation or a utility owned situation as you made no mention of a meter. Not a combination of the two. If it is utility owned let them do what they want. If customer owned do what you know is right.
Thanks for the response. This is a customer owned primary service there is a pole mounted fusible cutout that feeds a new 15kv primary load break switch (2 compartment one for the switch/fuse and one for the pt/ct?s and associated heaters) this feeds a outdoor xfmr. Located approx. 20? away with the primary metering backboard located within the facility. I know on a typical secondary service where the utility owns the xfmr. They want their own ground mat (for what reasons I do not know feel free to shed some light on this). But with a primary service I do not see how the two could be separated the switch enclosure is bonded to the ground ring, the associated primary and secondary feeders are grounded to the enclosure and then at the xfmr. There is a ground ring for the xfmr. pad where all the associated secondary and primary feeders eventually ground to also. I believe this is the correct way just wanted to get some opinions.
We have several of this type of installation. I can tell you what the practice is here.
You own the disconnect switch. You own the transformer. Both are on your property.
The service is at the your disconnect. The transformer is an SDS. The design of the grounding and bonding is up to you and the NEC. It doesn't matter where the metering is - that's just a contract issue.
Translating your question: If the utility owns the transformer, they want to separate the grounding of the transformer form the grounding of the facility. The only connection between the two grounding systems is the earth. What would that gain the utility? Why would it be different if the transformer were customer owned?
Only one reason I can think of. If the utility owns the xfm, then the NEC (for solidly grounded systems) requires the system be bonded at the forst disconnect. And of course, the utility bonds at the xfm. So with a fat ground mat between the utility xfm and the facility ther is a parallel path for the neutral current. Bad Science, but meets the NEC. So, the utility likely tells the customer to separate the grounding between the utility xfm and the facility - so there is no parallel path.
If you own the transformer, there is no problem. The transformer is an
SDS. The NEC requires you to bond the system in only one place - the xfm, the disconnect, or anywhere in between. Much better science.
My recommendation is to connect the grounding under the service disconnect, transformer, facility all together. Bond the xfm secondary at only one place. That is good science - good engioneering
carl
You own the disconnect switch. You own the transformer. Both are on your property.
The service is at the your disconnect. The transformer is an SDS. The design of the grounding and bonding is up to you and the NEC. It doesn't matter where the metering is - that's just a contract issue.
Translating your question: If the utility owns the transformer, they want to separate the grounding of the transformer form the grounding of the facility. The only connection between the two grounding systems is the earth. What would that gain the utility? Why would it be different if the transformer were customer owned?
Only one reason I can think of. If the utility owns the xfm, then the NEC (for solidly grounded systems) requires the system be bonded at the forst disconnect. And of course, the utility bonds at the xfm. So with a fat ground mat between the utility xfm and the facility ther is a parallel path for the neutral current. Bad Science, but meets the NEC. So, the utility likely tells the customer to separate the grounding between the utility xfm and the facility - so there is no parallel path.
If you own the transformer, there is no problem. The transformer is an
SDS. The NEC requires you to bond the system in only one place - the xfm, the disconnect, or anywhere in between. Much better science.
My recommendation is to connect the grounding under the service disconnect, transformer, facility all together. Bond the xfm secondary at only one place. That is good science - good engioneering
carl
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