Research Of Fault Line Selection Of Phase To Earth Fault In Small Current Grounding System

The small current grounding system is used in underground mine power supply system,which has a high reliability.In such power supply system,phase to earth fault is the main fault and it may cause the electric shock and fire.The fault line selection is a method to improve the security of the mine by cutting off the fault line accurately,and it can lessen the areas of power cut.But the poor working environment and complex electromagnetic environment of underground mine power supply system are harmful to the recognition of weak fault signal,and the fault line selection is still a technical problem.The traditional methods have many limitations,and all of them are difficult to meet the requirements of the present.In this paper,a simplified mathematical model of the underground mine power supply system is established,and voltage and current characteristics are analyzed under the phase to earth fault.The advantages and disadvantages of the zero sequence reactive power direction method and the DC selection method are discussed.Furthermore,a novel fault line selection strategy is presented,which builds a communication network and uses information fusion technology to improve the accuracy.The presented strategy can distinguish the phase to earth fault and the insulation reduced of the three-phase lines.In order to verify the correctness of the proposed method,this paper uses EMTDC/PSCAD to build a system simulation model.The simulation results indicate that the proposed method is effective.Finally,the realization of DC current detection method,zero sequence reactive power calculation method and communication are discussed,and some relevant designs are given.