DVSilverstone
Electrical
Hello, this is a question regarding the interpretation of the NEC article 450.3, with connection to 368.17 and 240.4. Here is the situation (in California):
A 2000A busway (3ph+G) is to be connected to the secondary of a 1500kVA oil-filled transformer (12.47kV Delta/480V Y, Is~1809A).
Two parallel 800A MCCB's will be located a the end of the main busway run, some 100ft away from the xfo, inside a cabinet, feeding one equipment. A flange will be used to fit the busway on that cabinet and split the power to the two MCCB's. Each split will be cabled for about 1000A. Length of both taps: less than 5ft.
Along the 2000A busway, a 60A derivation will be tapped off and protected by a fused disconnect, to feed a smaller equipment.
According to the code, the sum of the protections on the secondary do not exceed 250% of Is, so the transformer is considered protected.
Do I need to add a specific protection for the main busway leaving the transformer?
Thanks!
A 2000A busway (3ph+G) is to be connected to the secondary of a 1500kVA oil-filled transformer (12.47kV Delta/480V Y, Is~1809A).
Two parallel 800A MCCB's will be located a the end of the main busway run, some 100ft away from the xfo, inside a cabinet, feeding one equipment. A flange will be used to fit the busway on that cabinet and split the power to the two MCCB's. Each split will be cabled for about 1000A. Length of both taps: less than 5ft.
Along the 2000A busway, a 60A derivation will be tapped off and protected by a fused disconnect, to feed a smaller equipment.
According to the code, the sum of the protections on the secondary do not exceed 250% of Is, so the transformer is considered protected.
Do I need to add a specific protection for the main busway leaving the transformer?
Thanks!
