ENA ER G74 : ISSUE 1 1992

Specifies an outline procedure for a computer-based method for calculating circuit breaker short-circuit making and breaking currents in three-phase ac power systems having a nominal voltage range 380 V to 400 kV. These currents are used for assessing the adequacy of switchgear to perform the required duty. The recommended procedure is also applicable for the calculation of short-circuit currents for other purposes, such as the determination of protection relay settings or the calculation of mechanical forces arising form short- circuit currents.