SMU/NX to Bay-O-Net coordination
SMU/NX to Bay-O-Net coordination
(OP)
For medium voltage [13,2KV] underground distribution which type of fuse coordinate better with the Bay-O-Net type? SMU-20 50Amps or NX-50?
Let's say I'm 2 to 3 miles away from the sub.
Thanks!
Let's say I'm 2 to 3 miles away from the sub.
Thanks!






RE: SMU/NX to Bay-O-Net coordination
RE: SMU/NX to Bay-O-Net coordination
Well my question is in general: What type of fuse do you use when coordinating with Bay-O-Net type fuse. I understand some people use smu type, others use nx type and so on. The same way for overhead some people like to coordinate with only type "T" and other with type "K", etc,. I just want to hear pro's and con's from the experts in this forum.
Thanks!
RE: SMU/NX to Bay-O-Net coordination
By the way, a Bay-O-Net fuse can actually be composed of two different fuses (dual element), with a CLF backup in series in the 353C or 358C.
RE: SMU/NX to Bay-O-Net coordination
RE: SMU/NX to Bay-O-Net coordination
The name bayonet means dual and it comes from the rifle with a knife over the muzzle used in the mid 17th century for close combat.
RE: SMU/NX to Bay-O-Net coordination
RE: SMU/NX to Bay-O-Net coordination
Application questions could include load and fault current requirements. Coordinating with fault indicators could also drive you toward an SMU instead of an NX. If you plot the curves remember the bayonet is limited to 3.5kA or less (depending on voltage level) and is intended to clear secondary faults, not all primary faults. As mentioned backup current limiting fuses may be required or recognition that the upstream device may have to clear primary faults because the bayonet does not have enough interrupting rating to handle it. The previous statement assumes you are coordinating a bayonet applied in a transformer for transformer protection as opposed to the installation of some manufacturers inexpensive padmounted fused sectionalizing switchgear using bayonet fuses. Personally, I don't like the cheap padmounted switchgear as it's too easy to have the fault current for primary faults to increase beyond the bayonet ratings and no one will recognize it.