Influence of series compensation devices on secondary cables in case of single-phase short-circuit fault

Abstract

The installation of a Series Compensation Device (SCD) results in the series capacitive reactance offsetting a portion of the line inductive reactance. In the event of a single-phase short-circuit fault in a system equipped with an SCD, the potential for significant increases in fault current to ground exists if the SCD is unable to respond in a timely manner. This could lead to more severe safety concerns for both the equipment and personnel within the station. In order to clarify the influence of SCD on the secondary cable of the substation, this paper calculated the distributed capacitance and inductance of the secondary cable using the theory of multi-conductor transmission lines. A multi-conductor transmission line model of the secondary cable was established. Additionally, a grounding grid model that accounts for the mutual inductance between the primary grounding grid and the secondary as well as other point grounding grids was constructed. Subsequently, the oscillation frequency of the low-frequency component of the series compensation was derived using the Laplace method. Finally, the impact of varying degrees of series compensation on the interference of secondary cables is investigated by examining the alterations in fault currents and their induced ground potential rise following the installation of SCD. The above research provides a theoretical basis and analytical foundation for preventing SCD interference to substation secondary cables and proposing suppression measures.