DIN EN 60909-3:2010-08

Part 3 of DIN EN 60909 (VDE 0102) describes methods for calculation of the prospective short-circuit currents with an unbalanced short circuit in high voltage three-phase AC systems, that is the calculation of a) two separate simultaneous line-to-earth short circuits in isolated neutral or resonant earthed neutral systems and b)partially short-circuit currents flowing through earth in case of single line-to-earth short circuit in solidly earthed or low-impedance earthed neutral systems. The aim of this standard is to introduce practical and short calculation methods, which yield sufficient accuracy for results which are on the safe side. The calculated currents are used when determining induced voltages or touch or step voltages and rise of earth potential at a station (power station or substation) and the towers of overhead lines. In addition, procedures are given for the calculation of reduction factors of overhead lines with one or two earth wires. Moreover, the calculation of reduction factors of the sheaths or shields and in addition the current distribution through earth and the sheaths or shields of three-core cables or of three single-core cables with metallic non-magnetic sheaths or shields earthed at both ends are introduced. Part 3 is a supplement of DIN EN 60909-0 (VDE 0102); therefore the general terminology, formulas and mathematical assumptions refer to this publication. The responsible committee is Subcommittee UK 121.1 "Kurzschluss-Strom-Berechnung" ("Short-circuit current calculations") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.