short circuit happened in of the tube lights in air handling unit and it tripped the substation feeder which is Air circuit breaker. it rating is 200AT/800AF. its setting for instantaneous setting is 400 amperes. the details are as under:
Substation feeder breaker rating: 200 AT/800 AF.
Substation feeder breaker setting: 200 x 2 = 800 A (Instantaneous)
Distribution panel main breaker rating: 60 A
Branch circuit breaker rating: 20 A
Short circuit fault current: 1007 A
The question is why it did not trip the branch breaker or the main breaker of the distribution panel.?
Substation feeder breaker rating: 200 AT/800 AF.
Substation feeder breaker setting: 200 x 2 = 800 A (Instantaneous)
Distribution panel main breaker rating: 60 A
Branch circuit breaker rating: 20 A
Short circuit fault current: 1007 A
The question is why it did not trip the branch breaker or the main breaker of the distribution panel.?