Forum members,

In reviewing the defined parameters of Table 130.7(C)(15)(A)(b), I noted that several of the Equipment parameters requiring Category 1 and 2 PPE don't seem real-world. The requirement that the maximum clearing time be 2 cycles (0.03 sec) seems like it would only apply to fuse protection and not to a molded case circuit breaker (other than some type of smart breaker). I am wondering if the Equipment parameters noted in these instances are actually only referring to fuse protection, and if so, I think it might be best to stipulate.

I would appreciate your input,

Small molded case breakers (generally under 100 A) typically operate in 1-2 cycles so nothing wrong with the entries at all. It's only when you get into the larger frame sizes where the physical movement becomes a limiting factor that clearing times extend out to 3-5 cycles, or even up to 10-12 cycles for older breakers and a lot of higher voltage SF6 breakers. That's one of the major benefits of vacuum interrupters for higher voltages and currents...the physical contacts only move about 1/4 to 3/8" and once they separate at the next current zero crossing, the arc clears so typical specifications list 3 cycles for opening time with vacuum. I wouldn't even bother with a Limitamp or similar air breaker for medium voltage or over 800 A frames.