Non-communication protection of coal mine DC distribution lines based on transient current derivation

The fault current of coal mine DC power supply and distribution lines has the features of large amplitude and high rise rate, which is an important factor threatening the safety and stability of the power supply system. The method of using electrical features of DC distribution systems to achieve fault recognition rarely considers the actual situation of protective equipment. It makes it difficult to handle equipment errors and disturbances, and it does not meet the reliability requirements of relay protection. The active protection methods based on power electronic converters rarely utilize fault electrical information and rely solely on equipment action features to achieve fault removal. It often fails to meet the quick action requirements of relay protection. In order to solve the above problems, a non-communication protection scheme for coal mine DC distribution lines based on transient current derivation is proposed. The second derivative of the discharge current of the parallel capacitor on the DC side is used as the protection acceleration criterion. If the acceleration criterion is met, it will start the acceleration action. If the acceleration criterion is not met, it will act according to the established delay of the circuit breaker. When a fault occurs, the current is directed towards the fault point. The change in power flow direction can be used to preliminarily determine the direction of the fault, forming a non-communication protection. It will accelerate the tripping of the circuit breakers at both ends of the fault line, thereby shortening the fault removal time. The simulation results show that under different fault positions, transition resistors, and fault types, if the acceleration action can effectively start, the non-communication protection scheme of coal mine DC distribution lines based on transient current derivation can quickly remove faults and reduce fault time. If the acceleration action cannot be started, the protection scheme can also cooperate with the established delay to determine the fault type and section and remove the fault.