Grounding of non service rated medium voltage unit substation

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pete25

Member
I have an indoor mounted medium voltage unit substation that consists of three connected sections: a fused interrupter switchgear switch at 15kv in one enclosure , a 15kv to 480V stepdown transformer delta-Y which is connected to a 480V metal clad switchgear. The XO to ground bond is being done at the 480V switchgear which is then connected to a main ground bar in the electrical room which is tied to the grounding electrodes i.e. water pipe, building steel, exterior ground loop.

My question is does the medium voltage switchgear need to be tied to the ground bar also? Keep in mind that the incoming feeder 3Phase and Ground is coming from the site utility service switchgear and grounded transformer (delta pri., Y secondary) upstream. My thought it is not required to be tied to main ground bar as it is grounded via the equipment grounding conductor coming in with the 3ph feeder.
 
Your utility is low side grounded wye and your service supply point is the high side of the 15kV - 480V transformer?

Where is the neutral on the utility's low side terminated?
 
Elect117 said:
Your utility is low side grounded wye and your service supply point is the high side of the 15kV - 480V transformer?

Where is the neutral on the utility's low side terminated?
Click to expand...
No, this is not consider service equipment. The unit substation is fed from a remote service switchgear supplied by service step down transformer. The transformer is grounded.
 
Does the switchgear have a neutral ran to it?

I am guessing this feeder starts outdoors and enters inside to this unit substation?
 
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