2. Modelling of Transmission Systems Under Unsymmetrical Conditions and Contingency Analysis Using DIgSILENT PowerFactory

DIgSILENT PowerFactory is a powerful software which includes a power system analysis function designed to cope with large power system power flows, and it handles both DC and AC lines, including all phase combinations (3ph, 2ph and single phase), with/without neutral conductor and ground wires, for both single circuit and mutually coupled parallel circuits. Although power systems are designed and normally operated in balanced (symmetrical) three-phase sinusoidal conditions, there are certain situations that can cause undesired conditions, namely the unbalanced conditions. Uneven distribution of single-phase loads is one of the main unbalanced conditions in distribution level. The objective of this chapter is to provide an extensive review of the main features of steady-state analysis which are included in PowerFactory. Steady-state analysis in PowerFactory covers the normal operation (ComLdf) and the contingency analysis (ComSimoutage). This chapter has been divided into three distinct parts. The first part presents the main features of modelling overhead transmission lines (ElmTow, TypTow, TypGeo). Secondly, power flow analysis (ComLfd) under unbalanced conditions is illustrated. Finally, the third part of this chapter deals with the security assessment or contingency analysis for single time-phase contingency analysis. The deterministic assessment of failure effects under contingencies within a single period (ComOutage, ComNmink, ComSimoutage) is also analysed.