Four-Leg Transformer with Defined Zero Sequence Impedance for Ground Fault Compensation

Single-phase ground faults are the most common faults in medium-voltage distribution grids. High-impedance grid grounding using a special four-leg transformer is discussed in the paper. The transformer's zero-sequence impedance differs from positive-sequence impedance and it is designed to compensate the earth faults currents in Medium Voltage (MV) distribution grids when single-phase ground fault occurs. The designed transformer can replace the traditional arc suppression coils (ASC) in the case where no distribution transformer neutral is available or distributed compensation is required. Alternatively, the transformer can operate in parallel with the ASC.