Generator Bonding

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Prox

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Grand Rapids, MI
I will do my best to describe the service as it is installed, and am looking for some insight into where to bond the grounding electrode conductor the the grounded conductor. The utility service is a 13.4k high volt with a transformer and 4000 amp 480 volt main breaker secondary. Currently, bonding occurs in this section. At the end of the service gear lineup is a bus that ties to a 4000 amp breaker connected to the emergency distribution panel. The emergency source is 2 parallel generators. Square D has a plc that controls both breakers like a transfer switch. In addition, 11 other transfer switches, serving various loads added during different phases of construction over the last 20 years are connected to both utility and emergency. All of the transfer switches have solidly connected neutrals, and 3 of the switches are make before break switches installed under article 708 from the 2008 code. The theory in operation is that under a power failure, all the transfer switches are inhibited and the main breakers operate. If the system fails to transfer, the 11 switches are released and they transfer. I am being instructed by the engineer who came up with this system to install bonding jumpers between neutral and ground not only at the main breaker (4000 amp), but at the bus tie breaker and both generators. Since both generators are not part of a separately derived system (Neutrals are not switched at the 11 transfer switches nor in the direct bus through breaker scheme), my reading of the code says 1 bonding point at the main utility disconnect. Everything I can find about generator bonding concurs with this. Some help from the gurus with specific references would be wonderful. And yes, I hope to never see an installation like this again in my life.
 
Everything is solid neutral, from 10 of the 11 transfer switches (the fire pump switch doesn't have a neutral ran to it), to the buss connection from the EDP to the MDP. And yes, the concern I have is by adding the bonding jumpers, a crazy amount of unwanted current on the EGC would occur. Part of the engineered solution is a series of sensors, but that isn't going to stop the unwanted current, just let us know it is there.
 
Prox said:
Everything is solid neutral, from 10 of the 11 transfer switches (the fire pump switch doesn't have a neutral ran to it), to the buss connection from the EDP to the MDP. And yes, the concern I have is by adding the bonding jumpers, a crazy amount of unwanted current on the EGC would occur. Part of the engineered solution is a series of sensors, but that isn't going to stop the unwanted current, just let us know it is there.
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If the FP is fed from service with a ground, I believe this is a violation. {250.24(C)}
 
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