Revision Standard - Superseded. Superseded by 399-1997. This recommended practice is a reference source for engineers involved in industrial and commercial power systems analysis. It contains a thorough analysis of the power system data required, and the techniques most commonly used in computer-aided analysis, in order to perform specific power system studies of the following: short-circuit, load flow, motorstarting, cable ampacity, stability, harmonic analysis, switching transient, reliability, ground mat, protective coordination, DC auxiliary power system, and power system modeling.