Suppression of geomagnetic induced current using controlled ground resistance of transformer

Geomagnetically induced currents (GICs) in power systems can cause transformer-overheating malfunction of protective relays, tripping of protective devices, and voltage instability. This article presents a new approach by using a controlled resistance to suppress the GIC flowing through the neutral of transformers. The performance of the proposed method is compared with that of the currently adopted method, i.e., the fixed-capacitor method. In this work, a power network consisting of a single synchronous machine connected through a step-up delta/wye transformer, a double run transmission line and another step-down transformer to an infinite bus, is considered. The GIC is modeled as DC voltage pulses inserted in series with the line. The MATLAB/SIMULINK software is utilized to carry out simulations. Simulation results show that the proposed method is able to stabilize the system under GIC events. In addition, the new technique helps mitigate the zero sequence current flowing through the neutral of transformers during unsymmetrical faults. Moreover, the performance of the proposed method is better than that of the conventional method.