Blocking DC Flux due to Geomagnetically Induced Currents in the Power Network Transformers

Geomagnetically induced currents (GICs) in the power system cause half-cycle saturation of the transformers, malfunction of the protective relays, reactive power loss, and voltage instability. A DC Flux Blocker (DFB) that can be installed in series with the power system transformers tertiary windings to neutralize magnetomotive force (mmf) due to GIC is described. The device consists of two circuit breakers and a low power and high current voltage source, which provides the mmf of the GIC DC flux blocking function. The effectiveness of the proposed protective electrical device investigated and validated using the MATLAB software tool. The proposed method can effectively remove the flux due to GIC in both transformers and autotransformers that have tertiary windings. Since the proposed method does not alter the power system topology, it therefore has no effect on protection schemes.