Mitigation of Sympathetic Interaction between Power Transformers Fed by Long over Head Lines Caused by Inrush Transient Currents

Maintenance and operation of electrical systems in mining facilities fed by long Over Head Lines (OHL´s) require configurations with two or more power transformers for ensuring high reliability and availability. This work presents the methodology developed for the study of an actual problem related with the connection of three power transformers operating in parallel, addressing the phenomenon of sympathetic interaction when the DC-component of inrush transient currents of the incoming transformer generate additional saturation in the already connected transformers. Non expected operation and tripping of electrical protective devices may be caused by the asymmetrical voltages and prolonged transient harmonic overvoltages, affecting the reliability of the whole electrical systems. Simulation and experimental results of an actual power system validate the methodology proposed for the study and design of mitigation methods.