Abstract
The calculating formulae for short-circuit current are computerized by the shipyards or manufacturers of swicthboard according to IEC363 or others. When installing additional generators or motors, short-circuit current is calculated by computer again. If loss of accuracy can be tolerated, simplification on short-circuit current is given the useful guidance to the owners or users when applied to the confirmation or selection of switchgears. The effectiveness for simplifying short-circuit current at the generator busbars is considered on the basis of IEC 363 which has wholly revised at this time. Simplifying assumptions by direct-axis transient reactance of the generators or others are partly described in IEC 363.
