Grounding pole-mounted XFMR

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LISHAJI

LISHAJI

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Albany, NY
I came across a installation with reference to grounding and want to have the big picture view of it. Its a 1? 120/240 pole mounted transformer. Its neutral is not bonded to ground on the transformer. The bonding is done at the service disconnect about 250ft in the building. This installation should be at least 10 years old, no issues yet. What can be the consequences of not grounding the transformer neutral for this system?
 
Grounding at the transformer is not a specific code requirement. However, per 250.24(A)(2), a second grounding connection is required from the grounded service conductor to a grounding electrode.

This connection can be made either at the transformer or elsewhere outside the building. Since you don't have a connection at the transformer, I'd check to see if a second connection is made somewhere else outside the building.
 
I agree with Larry. Its unusual, it keeps me wondering why it was not done. As a consequence of not having a neutral grounded transformer, my hunch is that, if there is a ground fault on the underground secondary service lateral, the fault impedence would be too high to blow up the primary side fuse and the transformer would be feeding the fault for a long time or until it escalate into a bolted fault.
 
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If there are only 3 wires (LLN) from the transformer to the service disconnect bonding the transformer neutral to a grounding electrode will not help clear a ground fault on the secondary conductors. The earth does not conduct well at 120 volt.
 
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