Cable sizing from Switchboard to switchgear

[Tsukii]

Hello, everyone! I would like to ask on things to consider in sizing cable that connects switchboard to switchgear. Any formula or sample will be much appreciated. Thank you so much.

 

[tom baker]

That’s a short question with a long answer.
If you use the NEC we can help.
What is the size feeder breaker to switchgear?
Have you done a load Calc? (Art 220)
NEC ampacity tables are in Art 310

 

[augie47]

There are variations for motor or HVAC loads but the basic "formula" is to select a cable to carry the load and protect it at it's ampacity.
Thats a simplification as there are many variables involved..

 

[Tsukii]

That’s a short question with a long answer.
If you use the NEC we can help.
What is the size feeder breaker to switchgear?
Have you done a load Calc? (Art 220)
NEC ampacity tables are in Art 310

The switchboard is 12kV and the main feeder breaker is 12kV, 2000 A, 40 kA rms.

 

[tom baker]

That’s High Voltage application and the NEC may not apply. 2000A at 12Kv is a big load!

 

[electrofelon]

The switchboard is 12kV and the main feeder breaker is 12kV, 2000 A, 40 kA rms.

Take a look at 240.100 and 240.101