Applying Frequency Response Method For Contact Rails Fault Diagnosing in Ungrounded Electrical Railway System

General faults in regular electric railway systems can be detected by implementing the specific protection functions such as ground fault or sensitive earth fault. otherwise, in ungrounded electric railway systems which are using both feeding and return contact rails at the same time, fault detection cannot be performed with the above-mentioned function. due to recent growth in electric railway networks especially in metropolises, it is an essential requirement to improve operation and safety indexes by using efficient fault preventing and fault clearing method in minimum time. in this research, a new fault diagnosing method is developed by using frequency response of contact rail system. this technique is based on observing pattern changes that are caused by some expected faults such as the broken contact rail, contact rail to ground faults on feed or return circuit frequency response.