NSX100F-DC for battery breaker application with Galaxy VS UPS

[Yuri1]

Dear all, good morning,

I kindly request guidance from a Schneider Electric specialist regarding the appropriate use of the NSX100F-DC circuit breaker for a battery bank protection.

• 1) In an IT (isolated ground) system, such as an isolated battery bank (ungrounded poles) with 40x 12V 70Ah batteries in series (floating voltage 550Vdc, max voltage 600Vdc), and a maximum short-circuit current of 2kA, can the NSX100F-DC 3P (code C10F3D with TM100-DC trip unit) circuit  breaker be used safely to protect the battery bank? Assume that double pole-to-earth faults are not possible.

• 2) For reference, the Schneider manual for the standard battery cabinet model GVSCBC7D (for 40x 12V VRLA batteries, floating voltage 550Vdc) recommends using the NSX100S-DC three-pole breaker (part number C10F3S), rated for a battery bank that has up to 35kA short-circuit current. Given that in the above case the short-circuit current is much lower (max. 2kA), NSX100F-DC breakers were purchased. Can they still be used to protect the battery bank without any safety or performance issues? This battery bank is intended to supply the DC link for a Galaxy VS UPS.

•  Technical recommendations and advice are welcome.

Thank you very much for your assistance.

Best regards.