High Impedance fault detection Technique for the reliable power feeding in AT railway system

초록

Railway electrification was increased because of environmental-friendly, energy saving, and efficient of mass transport. Specially, railway electrification ratio in Korea reached to over 40% after KTX opening in April, 2004. Most electric railway system is operating AT feeding system exclusive of metro system, because it has the merits reducing the voltage drop and power loss and expanding the distance between substations. For the reliable operation in AT railway system, distance relay technique and △I fault selection technique are installed for main and backup protection relay. Also, fault locator is used for estimating fault location rapidly and minimizing fault clearance time However, protection relay can’t detect fault or cause malfunction in the normal operation condition because of various train operation conditions such as increase of train operation frequency, running of different control locomotives in the same feeding line, operation of generative and regenerative mode in the same time, etc. Especially, in the case of high impedance fault caused by the touch of tree, working vehicles, etc, protection relay can’t detect high impedance fault because fault current is very small. In this case, continuous arc can damage electric facility on the fault point and stop train operation at the worst. For the detection of high impedance fault, this research investigates characteristics of locomotive operation and fault situation. And we model AT feeding system using PSCAD/EMTDC and simulate the worst operation scenario among the various operation and high impedance fault conditions. We extract characteristics of high impedance fault and locomotive operation using simulation data and present the technique for detection high impedance fault using least square error method. In conclusion, this technique is going to contributes to the reliable power feeding in AT railway system.