Identification of symmetrical faults and overloads on parallel transmission lines based on compensated voltage cosine volume

To solve the problem of distance protection false operation or rejection caused by transition resistance during overload and fault, a distance protection scheme based on compensated voltage cosine volume to recognize overload and symmetrical fault is proposed. First, the trend of the current phase difference between two sides of the line with transition resistance is analyzed by phase quantity. Then, the minimum current amplitude ratio is utilized as the compensation coefficient to adaptively compensate the measured impedance angle in combination with the current phase difference. Finally, the relationship between the compensation coefficient and the transition resistance is used to determine the compensation degree to compensate for the measured impedance angle again, and the distance protection criterion is constructed by combining the voltage cosine volume. Using Matlab/Simulink, it is verified that this scheme is not affected by transition resistance, fault location, system operating conditions, and overload and can accurately recognize overload and symmetrical faults, with high tolerance to transition resistance.