Unless appropriate short-circuit backup protection is provided, protective devices shall have
adequate breaking (rupturing) capacity to interrupt the maximum fault current (including short-
circuit current) which can flow.
For PERMANENTLY CONNECTED EQUIPMENT or PLUGGABLE EQUIPMENT TYPE B, it is permitted for
short-circuit backup protection to be in the building installation.
For PLUGGABLE EQUIPMENT TYPE A, the building installation is considered as providing short-
circuit backup protection.