Hello! I've been away from eng-tips for a while, but thought this would be a good question for this group.
The 2017 NEC, paragraph 240.67 requires, starting in year 2020, that low-voltage fuse protection 1200A and larger have a means to reduce potential arc energy, similar to the present requirement for circuit breakers. The NEC suggests several means including differential relaying, energy-reducing maintenance switch, active arc mitigation, or approved equivalent.
The mechanism must be capable of interrupting calculated arcing current with 0.07 seconds. There are many cases where typical fuses will be too slow at the arcing current level. To my knowledge, most switches need at least 5 cycles to operate. It seems to me the only option will be some type of electronic "smart" fuse that can detect and operate for arcing current.
I'm just curious - Is anyone familiar with a present technology that could accomplish this without need for a circuit breaker?
Alan
The engineer's first problem in any design situation is to discover what the problem really is. Unk.
The 2017 NEC, paragraph 240.67 requires, starting in year 2020, that low-voltage fuse protection 1200A and larger have a means to reduce potential arc energy, similar to the present requirement for circuit breakers. The NEC suggests several means including differential relaying, energy-reducing maintenance switch, active arc mitigation, or approved equivalent.
The mechanism must be capable of interrupting calculated arcing current with 0.07 seconds. There are many cases where typical fuses will be too slow at the arcing current level. To my knowledge, most switches need at least 5 cycles to operate. It seems to me the only option will be some type of electronic "smart" fuse that can detect and operate for arcing current.
I'm just curious - Is anyone familiar with a present technology that could accomplish this without need for a circuit breaker?
Alan
The engineer's first problem in any design situation is to discover what the problem really is. Unk.
