CTRengineer
New member
A question about generator grounding point (not the grounded conductor). We have a project site that has an 800 Amp service panel fed from a 480v-3p-3w service transformer (secondary voltage). The existing building is industrial in nature with all lighting loads fed at 120v. No 277v loads or neutral existis for the 480v system. Note that because it's 800 amps, there is no GFI.
The building is receiving a new 500 KW 480/277v-3p-4w standby generator that feeds a 3-pole transfer switch. All emergency loads are fed by remote battery packs. The original design called for the neutral from the generator to be tied directly to the buildings main service ground bus on the second floor in the electrical room and is arranged as non-SDS. The contractor brought the generator equipment ground conductor out and connected it to the buildings ground grid, which is also tied to the wall mounted ground bus in the electrical room on the second floor. The generator has an 800A-3P output breaker.
Therefore, I see a ground loop so to speak and am concerned that if a line-ground fault occured within the generator, then fault current would flow via the ground conductor to the node where the building service transformer equipment ground is connected, thus potentially energizing all metal components connected throughout by virtue of the bonded conduit system.
The service transformer (500 KVS, 8,320/480 Delta-Delta) is also on the second floor as part of a unit substation. The contractor DID NOT provide a ground rod or grid at the generator pad as designed and thought he'd cheat by just "Grounding" the generator (not the "Grounded" conductor) to the building ground ring. Understanding that this IS NOT an SDS, should I be concerned about objectionable fault current flowing into building equipment via the equipment grounding system when a generator ground fault occurs.
Sorry for the lengthy discertation,
The building is receiving a new 500 KW 480/277v-3p-4w standby generator that feeds a 3-pole transfer switch. All emergency loads are fed by remote battery packs. The original design called for the neutral from the generator to be tied directly to the buildings main service ground bus on the second floor in the electrical room and is arranged as non-SDS. The contractor brought the generator equipment ground conductor out and connected it to the buildings ground grid, which is also tied to the wall mounted ground bus in the electrical room on the second floor. The generator has an 800A-3P output breaker.
Therefore, I see a ground loop so to speak and am concerned that if a line-ground fault occured within the generator, then fault current would flow via the ground conductor to the node where the building service transformer equipment ground is connected, thus potentially energizing all metal components connected throughout by virtue of the bonded conduit system.
The service transformer (500 KVS, 8,320/480 Delta-Delta) is also on the second floor as part of a unit substation. The contractor DID NOT provide a ground rod or grid at the generator pad as designed and thought he'd cheat by just "Grounding" the generator (not the "Grounded" conductor) to the building ground ring. Understanding that this IS NOT an SDS, should I be concerned about objectionable fault current flowing into building equipment via the equipment grounding system when a generator ground fault occurs.
Sorry for the lengthy discertation,