i am installing 5kv transformers outdoor to feed spray gun controllers and valves inside of wetting station vaults around the perimeter of a loadout pad for fgd product of a power house. my approved drawings dont show a detail on the grounding of these tranformers. they are a square-d one-piece unit with the panels made on them. they are fed with 20 amp double pole 480 breakers and have a 30 amp 120/240 secondary main. I'm wondering if they will require a ground rod at each station to bond each secondary xo to ground or if the ground coming with the 480 feed is sufficient? Ive never hooked up transformers this small, i didnt know if the rules were the same. there is nothing in the prints or in the papers with the transformers. nec wasnt clear on this situation
grounding 5kv transformer
- Thread starter lafe
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SG-1
Senior Member
- Location
- Ware Shoals, South Carolina
250.30
250.30
First I assume you are connecting a 5kva transformer, not a 5KV transformer.
250.30 is the code section you seek, Grounding Separately Derived Alternating-Current Systems.
250.30(A)(7) requires a grounding electrode and lists metal water pipes & structural steel as the perfered electrodes. Exception 1 allows any other electrodes identified in 250.52(A) to be used, which includes ground rods when the water pipe & steel are not present.
You need the ground rods especially since the transformer is located outdoors and will have little protection against transient overvoltage caused by lightning.
250.56 requires a second rod if the resistance of the first is above 25 ohms, spaced not less than 6ft. apart. If you cannot measure, then drive the second rod. This is your primary protection against lightning induced transient overvoltage.
Yes you are bonding the X0 to the grounding electrode conductor (ground) at the transformer.
Is the System Bonding Jumper already present between the X0 and the enclosure ?
Hope this helps,
Steve
250.30
First I assume you are connecting a 5kva transformer, not a 5KV transformer.
250.30 is the code section you seek, Grounding Separately Derived Alternating-Current Systems.
250.30(A)(7) requires a grounding electrode and lists metal water pipes & structural steel as the perfered electrodes. Exception 1 allows any other electrodes identified in 250.52(A) to be used, which includes ground rods when the water pipe & steel are not present.
You need the ground rods especially since the transformer is located outdoors and will have little protection against transient overvoltage caused by lightning.
250.56 requires a second rod if the resistance of the first is above 25 ohms, spaced not less than 6ft. apart. If you cannot measure, then drive the second rod. This is your primary protection against lightning induced transient overvoltage.
Yes you are bonding the X0 to the grounding electrode conductor (ground) at the transformer.
Is the System Bonding Jumper already present between the X0 and the enclosure ?
Hope this helps,
Steve
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