DC Circuit with parallel conductors in separate conduits

DattMtn

Member
Location
Colorado
Occupation
Engineer
Howdy, I am designing a system that has [10] parallel sets of 750kcmil Al conductors running between a BESS (Battery Energy Storage System) and PCS (Power Conversion System ie Inverter). I have a question regarding the EGC requirements for these [10] parallel sets, would a 500 kcmil Cu per PVC run (~30ft) be required? There are [11] 400A fuses in parallel as OCPD hence that sizing. We are debating this because there is 250.134 "Equipment Fastened in Place or Connected by Permanent Wiring Methods (Fixed) — Grounding…(B) With Circuit Conductors: By connecting to an equipment grounding conductor contained within the same raceway, cable, or otherwise run with the circuit conductors." Additionally exception 2 that states "that for DC circuits the EGC shall be permitted to be run separately from the circuit conductors".

Our main issue is that the equipment does not have provisions to land that many EGC's, and the manufacturer has stated that they don't even want any EGC. Additionally we do have a ground grid in this design and the chassis of each equipment is bonded to the ground grid.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Welcome to the forum.

I would think that an EGC (one or more) sized for the 4,400 amps' worth of fusing would suffice.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Do you mean parallel sets connected at both ends? Or is this really ten (or eleven?) separate circuits going into a 'combiner'. If the former, see 240.8, your design may not be compliant. (I think that's what texie was getting at).
 

DattMtn

Member
Location
Colorado
Occupation
Engineer
Nominal Battery voltage is roughly 1500VDC, it's a little lower than that but essentially there. Yes these sets are paralleled to be one circuit and are running through [10] different PVC pipes from the battery combiner to the inverter DC entry window. The output of the DC combiner is protected by [11] 400A fuses set in parallel to get the 4400A available current previously mentioned. Utility scale battery systems get pretty nutty pretty fast.
 
Top