Transient behaviour of a static compensator with ferromagnetic non-linearity

Static compensators using saturable reactors and capacitors are frequently used in power transmission systems for voltage stability and reactive power control. To be able to determine the behaviour of the compensator on-line computer programs has been developed which models the three phase, double zig-zag connected saturable reactor including the six magnetic cores. The iron and copper are properly taken into account to provide the right damping effect. The program determines the instantaneous behaviour, for instance the phase currents and the inductive field versus time. Steady state results are used to determine the overall voltage versus current and the harmonic content of the current. Transient behaviour are also computed. Agreement between theory and experiment on a 55 MVA/12 kV prototype is excellent. So far our program is able to simulate correctly the internal behaviour of the compensator and its influence on the line as well in steady state as in transients. This elaborate analysis can be further used to define simpler and less expensive tools more suitable for every day use.