TRANSFORMER AND MAIN PANEL GROUNDING

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AWinston

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Murrieta, Ca
I have a 2000A panel sitting right next to a 2MVA transformer. Do I need to run a ground from Transformer T2 to the 2000A panelboard? Both components are grounded independently. My thought is if I connect both components, there will be 2 fault paths which is a no no. It sounds like I answered my own question, but I want to be 100% sure and have no doubts. See attached screenshot of schematic.
 

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GoldDigger

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Two or more fault paths are almost never a bad thing. And earth grounds are only a valid fault clearing path at medium and high voltages.
Having two paths for normal current, on the other hand, is discouraged outside of POCO jurisdiction. (They have special electrons.) Whose transformer is it and where is the service disconnect?
If you run an EGC (raceway or wire) between them and bond EGC to neutral at both ends you will have a parallel path for normal current through the EGC.

PS: The lettering on your image is very hard to read, but I think that you may be talking about upstream of the service disconnect.
 
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AWinston

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Location
Murrieta, Ca
GoldDigger said:
Two or more fault paths are almost never a bad thing. And earth grounds are only a valid fault clearing path at medium and high voltages.
Having two paths for normal current, on the other hand, is discouraged outside of POCO jurisdiction. (They have special electrons.) Whose transformer is it and where is the service disconnect?
If you run an EGC (raceway or wire) between them and bond EGC to neutral at both ends you will have a parallel path for normal current through the EGC.

PS: The lettering on your image is very hard to read, but I think that you may be talking about upstream of the service disconnect.
Click to expand...

The transformer belongs to the customer. It is not the utility's transformer.
 
don_resqcapt19

don_resqcapt19

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retired electrician
It looks like the transformer is 480Y/277 and you will also need the neutral if there area any line to neutral loads.

If not, then the system bonding jumper would be installed at the transformer and the supply side bonding jumper(s) between the transformer and the gear. If you have non-flexible metallic conduits between the transformer and the gear, they are permitted to service as the required supply side bonding jumper.
 
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AWinston

Member
Location
Murrieta, Ca
don_resqcapt19 said:
It looks like the transformer is 480Y/277 and you will also need the neutral if there area any line to neutral loads.

If not, then the system bonding jumper would be installed at the transformer and the supply side bonding jumper(s) between the transformer and the gear. If you have non-flexible metallic conduits between the transformer and the gear, they are permitted to service as the required supply side bonding jumper.
Click to expand...

I already specified a neutral. That is another question I have. The client wants to remove the neutral to save money since they don't have 277V loads. The problem is that this is a massive solar project and I am not sure if the neutral has to be connected to the transformer for the inverters.
 
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