Current on EGC

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slect

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2 Gen sets connected to a 3-pole Xfer switch. 3-phase 4 wire with EGCs..
One gen set is bonded ( G-N).. The other is not. 250.20(d) fpn.1.
The Xfer switch feeds an MDP.. MDP feeds around 8 SDPs.. SDPs feed trailers.. EGC run w/all feeders from trailer all the way back to gen.
I have approximately .5 to 1,2 amps on each EGC that is run w/each SDP feeder cable that terminates at the MDP .. I have approximately 8 amps from MDP to Xfer switch.. and 8 amps on EGC from Xfer to Gen. ( the gen set that is running )..
When I disconnect all 8 EGCs coming from the SDPs at the MDP it reduces the current from the MDP to Xfer switch to 3 amps.. I also still have 3 amps from Xfer switch back to the gen set.. There are no bonding jumpers in the trailers or anywhere else in the system.. I cant find any leaks to ground at the trailers..When all EGCs are disconected from the MDP why do I still have 3 amps going back to Gen ? Is that current coming FROM the bond at the gen set and using the Xfer switch and MDP as another source to ground ? Is my grounding electrode resistance at the genset too high so its looking for a lower resistance path ? I have moved the EGCs away from phase conductors as much as possible to avoid induction.. any thoughts ? :-?
 
Current on EGC

The system voltage is 230/400 3-phase 4 wire..
There is approximately 200-400-- amps per phase depending on occupancy, weather , etc.... 20-40 amps on neutral..
 
Current on EGC

To expand on this a little.. I dont remember inspectors ever checking for current on the EGCs.. I have not been spot checking it myself when completing projects although I will make it a habit now,, Does any current on the EGC indicate a problem ? Or is a small amount in relation to the phase conductor thru induction unavoidable in larger systems ? Big enough but not quite meeting the requirement GFCI protection...
 
Corrent on EGC

Corrent on EGC

Excessive current on the EGC would indicate that an incorrect bonding jumper is installed down stream in one of the sub-pnels. Also, either thru a mistake when installing devices, or a nick in the neutral wire, a neutral could be connected or touching to an EGC creating objectionable current ( 250.6). In my first post I cant seem to find any of these causes in the above project. Looking for other thoughts or ideas.. With no EGCs connected to the panels downstream I still have current from MDP back to Generator... Also, there are additional power sources supplying other areas.. Could leakage from that other source find its way back on to one or more of my ground rods ?
 
Prize !

Prize !

Do I win some type of prize for stumping the entire forum with this question ?

95 views and not one sugestion.. wow....interesting...;)
 
If you can, remove the bonding of the service neutral to ground and see if it goes away. If it does, it's coming in on your service neutral. This is assuming your service feeders do not have an equipment ground conductor and are not installed in a metal raceway.
 
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