Utility Scale Battery Storage

[ron]

This is an MV XFMR so we need to use the MV table (NEC 450.3(A)). The MV XFMR table is more liberal with the protection requirements. The notes are pretty much the same though.

Looking at the oneline on the first post, it looks like a 480V secondary, so I would use 450.3(B)

 

[wwhitney]

Looking at the oneline on the first post, it looks like a 480V secondary, so I would use 450.3(B)

Since Table 450.3(A) has columns for "Primary Protection Over 1000V" as well as separate columns for secondary protection "over 1000V" and "1000V or less", looks like Table 450.3(A) applies whenever the primary side is over 1000V.

Cheers, Wayne

 

[ron]

Since Table 450.3(A) has columns for "Primary Protection Over 1000V" as well as separate columns for secondary protection "over 1000V" and "1000V or less", looks like Table 450.3(A) applies whenever the primary side is over 1000V.

Cheers, Wayne

Good point, thanks

 

[bkg73123]

Just so I am clear. The proper approach to sizing the conductors is to take the load (the greater of the BESS' input or output), which in this example is 1,963 FLA. Then determine the next highest sized OCPD, which would be 2,000 A. Then determine the proper and size conductors, which in this example one solution would be 4 parallel runs of 700kcmil 90F CU cable (2,080 ampacity). Then if an OCPD is required on the secondary of the xfmr, it would be the same size of 2,000 A. ???

In regards to the GND wire I would have chose a single 250kcmil CU wire since I was using Table 250.112 Minimum Size EGC for Grounding & Equipment, but as pointed out by pv_n00b, this is not an equipment ground. It is a bond. Is there such a table for bonding wires? Or can I please get an example of how to calculate the BOND/GND wire size (conservatively not exactly) as mentioned here: "Since the XFMR represents a separately derived system (NEC 250.30) the grounding conductor is a supply-side bonding jumper and is not an EGC sized to an OCPD rating. It is based on the size of the current carrying conductors from the XFMR to the BESS. The XFMR being much larger than a single BESS is going to dominate a lot of the calculation. Then there is the additive component. Each circuit from the XFMR to a BESS is exposed to fault current from the XFMR plus (n-1) times the BESS fault current."


Thank you!

 

[kingpb]

Something I notice that raises a red flag is, cable tray. Not ta bad idea IF the BESS container is elevated. If on ground, I would consider utilizing trench (trenwa) style.

 

[pvsolarpro]

bkg73123 interested in finding out what your final count and size of parallel conductors you went with. Thanks​