Power Supply System Relay Of The Metro Tuning With Research

With the increase of subway departure density caused bydeteriorating urban transportation, the traction power supply system ofsubway is facing a severe challenge brought by its high load operations,thus a more reasonable protection scheme is in urgent need to protect thepower supply system. In this paper, regarding DC traction power supplysystem of subway as research object, the relay protection of DC side andAC side have been detailed analyzed and the set of protectioncoordination by their respective characteristics has been achieved.According to the detail analysis of DC side relay protectionconfiguration, two problems can be found in the traditional DC sideprotection modes: the first is that the short-circuit fault protection cannotbe achieved better in network feeder distal, the second is that malfunctionrate of protection is higher because the oscillation current cannot beidentified accurately. Based on this, the combined protection of di/dt andΔ I is proposed to solve the distinguish problem of the distal short-circuitfault effectively, and the EMD (empirical mode decomposition)protection algorithm is presented using extract mode feature vector ofoscillation current and short circuit current to solve the malfunctioncaused by oscillation currents better in paper. The experimental resultsprove the efficiency of the above two kinds of protective method.As AC side of the relay protection is also susceptible to malfunction affected by the magnetizing inrush current, magnetizing inrush currentsignal, the normal operation current and short circuit current signal aredecomposed by wavelet packet and the energy value of variousfrequency-domain is calculated. The energy spectrum shows that thefrequency characteristics of magnetizing inrush current is significantlyabundant, thus magnetizing inrush current can be effectively identifiedaccording to its energy distribution.Considering the possibility of refusing action during operation,protection coordination programs is proposed to reduce it, and protectionalgorithm setting value is set according to the features of variousprotection and the needs of power supply system, what’s more, thereasonable of protection coordination programs is verified by simulation.In addition, as the simulation of transient current of different powerdistance and different positions is needed to analysis DC traction powersupply system, mathematical model of traction network is establishedand the transient current simulation of traction network short-circuitsituation is achieved using LabVIEW.