I am looking at a inside of an industrial facility where we are replacing the main feeders to a 2000A 12.47kV Switchgear lineup. The new feeders will be (3) sets of 750MCM cables. It is my understanding that.
Per 250.190(C)(3) table 250.122 shall be used to size the EGC based on the setting of the fuse or the setting of the overcurrent relay. This particular feeder is fed from a breaker which will have a 2000A pickup setting on the protective relay.
Based on this 250.122 requires a 250MCM cable based on the 2000A setting of the feeder relay. Since these cables will be run in (3) separate conduits as part of a parallel feeder it is required per 250.122(F) that each parallel feeder and conduit have a 250MCM ground run with it.
Am I understanding this right? Something seems odd that this large of an EGC would be required in relation to phase conductors. We are also considering running (4) sets of 500MCM instead for phase conductors which would still require 250MCM EGC due to 2000A setting. If 500MCM cables are use the 250MCM EGC in each conduit would be almost as large as the phase conductors?!?!
Per 250.190(C)(3) table 250.122 shall be used to size the EGC based on the setting of the fuse or the setting of the overcurrent relay. This particular feeder is fed from a breaker which will have a 2000A pickup setting on the protective relay.
Based on this 250.122 requires a 250MCM cable based on the 2000A setting of the feeder relay. Since these cables will be run in (3) separate conduits as part of a parallel feeder it is required per 250.122(F) that each parallel feeder and conduit have a 250MCM ground run with it.
Am I understanding this right? Something seems odd that this large of an EGC would be required in relation to phase conductors. We are also considering running (4) sets of 500MCM instead for phase conductors which would still require 250MCM EGC due to 2000A setting. If 500MCM cables are use the 250MCM EGC in each conduit would be almost as large as the phase conductors?!?!