Utility Transformer, Parallelling Switchgear, and 2 Generators - N/G Bonding

[SparkyGlobal]

Scenario 1:
Incoming Utility through a distribution transformer,(MV to LV, Wye, 4Wire), then to a 4Pole breaker at a Paralleling Switchgear.Two generators (G1 and G2) connected through 3Pole breakers on the generators and in the Paralleling Switchgear.

The generators have an integral 3Pole Breaker with power monitoring to over voltage, under voltage, ground fault, etc…
The AHJ adamantly requires neutral/grounding bond at the transformer secondary side.

When utility power is out, the Paralleling Switchgear starts generator 1 , opens the utility 4Pole breaker, closes Generator 1 breaker, and power is provided via Generator 1.

Issue 1: The opening of the utility 4Pole breaker disconnects the neutral/grounding bond from the circuit. The neutral is now floating. If maintenance or testing of generator 2 were needed, even if generator 2 3Pole paralleling switchgear breaker was locked and tagged out, the crew would be working in and around a neutral under live load. If they accidentally create a solid path from neutral to grounding (generator frame, etc...), there is no ground fault protection and a shock hazard exists.

True or False?

 

[shortcircuit2]

Neutral goes through a breaker?

 

[ghorwood]

Something is missing. A schematic of the paralleling gear would help.

 

[cuba_pete]

Generator neutral should land on the neutral bus downstream from the incoming mains. The generator as a source is not related to the incoming transformer. You are in island mode when normal power is not available.

 

[truck41trouble]

So.... Since the neutral is switched, this counts as a seperately derived system right? There should be grounding means at the generator , so when the generator is running there won't be a " floating " neutral, when the generator closes in, it creates the bond.Your utility ground normally isn't the only grounding means for a site anyway. As far as generator 2 is concerned, for maintenance purposes either remove all leads, or add removable links to isolate that generator.

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