Design On The Relay Protection Scheme Of Combined Co-Phase Power Supply System

This paper analyzes relay protection of combined co-phase power supply system. In the new power supply scheme, balance traction tranceformer is replaced by single-phase transformer and high voltage matching transformer (HMT) with the appropriate amount of compensation devices to realize the co-phase power supply technology. As main wiring of the traction network changes, the occuring of Traction Matching Transformer (TMT) and compenstion bus and the different stanby mode of co-phase power supply device (CPD), the traditional power supply protection scheme and setting principles should be restudied.First, operating principles and advantages of combined co-phase power supply system are analyzed. Then the basic struture, the cascade structure of ADA, the active current separate approachand the common PWM control methods are introduced. A model is constructed using Matlab/Simulink to validate the feasibility of this system and the correctness of under sixteen types of operation modes of the power supply system.Secondly, the influences of the access of CPD to the power supply system is analyzed The ADA device adopts the pulse blanking method under the overcurrent condition, this method can prevent the refusal-operation of transformer back-up protection when feeder line protection mis-operates. In order to satisfy the demand of this new relay protection, a protection scheme for HMT with differential protection, gas protection and low-voltage overcurrent protection is designed; active power differential protection and overcurrent pulse atresia protection are used for CPD; adaptive distance protection, rate of current rise protection and overload protection are implementedfor feeder line. The active power restraint is adapted in CPD protection scheme to prevent active power differential protection mal-operation.Finally, a model of combined co-phase power supply system is constructed and simulated in RTDS. The current matching relation is proved to be correct, and combined co-phase power supply system is validated to be effective. The CPD protection scheme, HMT and Traction Transformer (TT) protection scheme are processed in RTDS, and simulation results demonstrate these protection schemes are applicable to the real combined co-phase power supply system.