Extension of the Unmatched-Media Time Reversal Method to Locate Soft Faults in Transmission Lines

An alternative method based on time reversal to locate solid faults in transmission line networks was recently proposed by Codino et al. in the paper “An alternative method for locating faults in transmission line networks based on time reversal” (IEEE Trans. Electromagn. Compat., vol. 59, pp. 1601-1612, 2017), in which different media for the forward and backward propagation phases are considered. The main advantage of the method is that it requires only one simulation for the time-reversed backward propagation to locate the fault. In this paper, we propose an extension of the Codino et al.'s approach to locate soft faults, characterized by a nonzero fault impedance. A closed-form expression for the time-reversal transfer function is derived. This new transfer function benefits of the same properties associated with solid faults and, hence, can be used for locating soft faults along the line. Three different scenarios are considered: a 6.5-km-long power line, a 100-km-long power line, and a microstrip line for high-speed digital signals. The results are discussed and used to assess the accuracy and scalability of the proposed method.