Service Grounding

[amsco]

I have an existing 1600A, 480V delta, 3-phase, 3-wire ungrounded service, with ground detection system, fed with 4 sets of 3?C-3#600kcmil overhead. I discovered a separate 2?C-1#500kcmil feed from the utility?s grounded conductor (the same transformer bank serves a wye service at another building) overhead, bonded to the service?s C/T cabinet. While this separate feed clearly provides a ground fault path, does this meet the Code or make the service safer? No grounding electrode system was observed

 

[don_resqcapt19]

I don't understand. If the same transformer bank provides power to both buildings, then the system is a grounded system and you should have a grounded conductor run with each of the sets of phase conductors.

 

[chris kennedy]

I have an existing 1600A, 480V delta, 3-phase, 3-wire ungrounded service, with ground detection system
(the same transformer bank serves a wye service at another building)

How can the transformer bank be both?

fed with 4 sets of 3”C-3#600kcmil overhead. I discovered a separate 2”C-1#500kcmil feed from the utility’s grounded conductor

The single conduit and conductor seems to violate 310.4.

While this separate feed clearly provides a ground fault path, does this meet the Code or make the service safer? No grounding electrode system was observed

250.24(A) would require the grounded conductor be brought to the service.

250.24 Grounding Service-Supplied Alternating-Current Systems.
(A) System Grounding Connections. A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).

But there seems to be a conflicting code article in 250, go figure.:smile:

250.20 Alternating-Current Systems to Be Grounded.
Alternating-current systems shall be grounded as provided for in 250.20(A), (B), (C), (D), or (E). Other systems shall be permitted to be grounded. If such systems are grounded, they shall comply with the applicable provisions of this article.
(B) Alternating-Current Systems of 50 Volts to 1000 Volts. Alternating-current systems of 50 volts to 1000 volts that supply premises wiring and premises wiring systems shall be grounded under any of the following conditions:
(1) Where the system can be grounded so that the maximum voltage to ground on the ungrounded conductors does not exceed 150 volts
(2) Where the system is 3-phase, 4-wire, wye connected in which the neutral conductor is used as a circuit conductor
(3) Where the system is 3-phase, 4-wire, delta connected in which the midpoint of one phase winding is used as a circuit conductor

Your grounded conductor doesn't appear to be a circuit conductor.

These comments are based on the assumption the costumer owns the wire to the weatherhead.

Edit: Darn it Don, I have been working on this for 30 mins.

 

[infinity]

Sounds like they brought in 3 phase, 3 wire from a WYE system. Would a neutral conductor be required if the system is setup to operate as an ungrounded system?

 

[don_resqcapt19]

Sounds like they brought in 3 phase, 3 wire from a WYE system. Would a neutral conductor be required if the system is setup to operate as an ungrounded system?

It sounds like XO is grounded by the utility at the transformer making it a grounded system and requiring the grounded conductor to be run to the service disconnect(s).