§ 111.51-3 Short-circuit calculations for systems below 1500 kilowatts.
The following short-circuit assumptions must be made for a system with an aggregate generating capacity below 1500 kilowatts, unless detailed computations in accordance with § 111.51-4 are submitted:
(a) The maximum short-circuit current of a direct current system must be assumed to be 10 times the aggregate normal rated generator currents plus 6 times the aggregate normal rated currents of all motors that may be in operation.
(b) The maximum asymmetrical short-circuit current for an alternating current system must be assumed to be 10 times the aggregate normal rated generator currents plus 4 times the aggregate normal rated currents of all motors that may be in operation.
(c) The average asymmetrical short circuit current for an alternating-current system must be assumed to be 8 1/2 times the aggregate normal rated generator currents plus 3 1/2 times the aggregate normal rated currents of all motors that may be in operation.