Grounding electrode at transformer

[Richard Smith]

The question arose yesterday about the requirement of having a grounding electrode installed for an interior step down 3 phase transformer. The foreman on the job says that the transformer doesn't require it's own gounding electrode. I've always grounded transformers and am confused at his instructions. Can someone help me out without making this more confusing?

 

[roger]

With the exception of an ungrounded Delta (which I doubt you are refering to) the Separately Derived System (Transformer) must be connected to a Grounding Electrode, see 250.30.

Roger

 

[Richard Smith]

I was reading an archived article on this site earlier between two senior experts here and the one named BENNIE was saying that the transformer wasn't an sds. It left me not sure that I knew what I thought I knew.

 

[roger]

I was reading an archived article on this site earlier between two senior experts here and the one named BENNIE was saying that the transformer wasn't an sds. It left me not sure that I knew what I thought I knew.

Bennie was a well respected member and was arguing the actual definition of what an SDS is. The reality is, the NEC considers it an SDS and 250.30 would be applicable.

Roger

 

[weressl]

The question arose yesterday about the requirement of having a grounding electrode installed for an interior step down 3 phase transformer. The foreman on the job says that the transformer doesn't require it's own gounding electrode. I've always grounded transformers and am confused at his instructions. Can someone help me out without making this more confusing?

The transformer does not require its own grounding electrode, however it requires a solid connection to the ground. In other words if it is located, say, on the third floor it may be connected to the building steel or grounding wiring as long as those are bonded to a driven grounding rod or other approved metallic objects that qualify as grounding electrode.