Combination Faults Protection Method Based on Negative Sequence Impedance Angle in Resonant Grounding Distribution System

Overvoltage in the distribution network of arc suppression coil grounded system may result in single-circuit arbitrary two points earth faults. If two fault points fall on different line sections, the first section of the faulty line protection will have the problem of rejection. In order to enable the protection to operate, a negative sequence impedance angle-based protection method is presented for single circuit arbitrary two points earth faults in arc suppression coil grounded system. Firstly, We establish a compound sequence network and a negative sequence network with single circuit arbitrary two points earth faults. Following this, the analytical expressions for the negative sequence current at the first end of the line and the negative sequence voltage at the bus bar are derived. Then by dividing the negative sequence voltage by the negative sequence current at the busbar at the head of the line, the negative sequence impedance of the line can be determined. PSCAD simulations show that the proposed protection method is independent of the location of the point faults and the transition resistances, as well as having low communication requirements.