Study on the effect of the failure of commutation on the phase selection of the current mutation

In order to improve the reliability of power supply, automatic coincidence technology is widely used in high voltage transmission lines. In the distance protection, in order to make the measuring element accurately reflect the fault distance, it is necessary to find out the fault loop and distinguish the fault phase. Therefore, the phase selection element is indispensable in the distance protection logic, among which the phase selection element based on the current mutation has been widely used in the distance protection. This paper first introduces the principle of phase selection of current mutants and then reveals the mechanism of the effect of the failure of commutation on the element of current mutants. The analysis shows that the strength of AC system will affect the phase selection performance of the current phase selector during the failure of commutation. Finally, a solution based on voltage phase selection is proposed, and the simulation results show that the new phase selection method is more suitable for AC/DC hybrid system, and can achieve the purpose of phase selection correctly.