Grounding at Paralleling switchgear

[anbm]

We have (3) emergency generators feed the paralleling gear, the gear then feed several ATSs (ATS has neutral wire to be switched). Generators are considered to be separate derived system.


1. Should we drive ground rod at each E.G. location and bond each generator to the rods?


2. Can omit item 1. above and only run the ground wire from paralleling switchgear ground bar and bond to building ground? (assume the neutral and equipment bars are bonded inside paralleling switchgear). Will this violate NEC because of ground loop?


PS: ATS also served by building utility power sources when not in emergency mode.

Thanks!

 

[RUWired]

ANBM, where is the OCPD for each of the generators.
If the OCPD's are in the parallel gear, you can install the system bonding jumper in either the parallel gear or in the generators.
If the OCPD is at each gen set, the bonding jumper goes in the gen sets. Once the bonding jumper is established, that will dictate where the grounding electrode system ties into. You can install a seperate grounding electrode conductor for each set or use a common grounding electrode conductor for all three. If you use a common GEC, the wire size changes from an individual GEC. If you can put the bonding jumper in the parallel gear only one Grounding electrode system will be required.
From the point of the system bonding jumper on out the grounding and grounded conductor will be seperate and also into the building. Hope this helps

Rick

 

[anbm]

Each generator shall have its own OCPD (regular thermal magnetic breaker), and each generator section inside paralelling gear also has its own OCPD to serve generator (this is motorized breaker).

 

[RUWired]

Each generator shall have its own OCPD (regular thermal magnetic breaker), and each generator section inside paralelling gear also has its own OCPD to serve generator (this is motorized breaker).

Since the OCPD is at each of the generators, the system bonding jumper and the grounding electrode system is required at each of the generators.(250.30(A)1 and (A)3. You can use a common electrode conductor as required in 250.30(A)4.
The outdoor paralleling set should have the grounded and grounding conductors seperated. A grounding electrode conductor should be installed per 250.32(A) and can be tied into the common electrode system of the gensets but tied into the equipment grounding conductor only.250.32(B)
The equipment grounding conductor in the ats's should be seperate as well providing there is a main breaker and distribution equipment prior to the ats's. Hope this helped.
Rick