The paper presents a new method based on the Electromagnetic Time-Reversal (EMTR) for locating faults in power systems. The applicability of the EMTR to electromagnetic transients associated with traveling waves in transmission lines originated by the fault is theoretically demonstrated. A new fault location technique is then proposed and illustrated for a simple case of a singleconductor transmission line, for which the performance of the proposed technique in terms of location accuracy is discussed. The use of the EMTR technique appears to be particularly promising for locating faults in passive and active electrical distribution networks in view of their radial structure.

Abstract-This paper presents a new method based on the electromagnetic time-reversal (EMTR) theory for locating faults in power networks. The applicability of the EMTR technique to locate faults is first discussed. Using the classical transmission-line equations in the frequency domain, analytical expressions are derived to infer the location of the fault. The accuracy of the proposed method is then discussed in relation to the number of observation points adopted to record the fault-originated electromagnetic transients. Then, this paper illustrates the extension of the proposed method to the time domain. The experimental validation of the proposed method is presented by making reference to a reduced-scale coaxial cable system where real faults are hardware-emulated. Finally, the application of the proposed EMTRbased fault-location method to Electromagnetic Transients Program-simulated cases is presented. The simulated test cases are: a mixed overhead/coaxial cable transmission system and the IEEE 34-bus distribution test feeder. Compared to other transient-based fault-location techniques, the proposed method presents a number of advantages, namely, its straightforward applicability to inhomogeneous media (mixed overhead and coaxial power cable lines), the use of a single observation (measurement) point, and robustness against fault type and fault impedance.

Significant research has focused on the diagnosis of "hard" faults (open and short circuits) in transmission lines, but there has been much less work on "soft" faults resulting from a very small change in line impedance. This research is based on one type of soft fault problems in electrical fault diagnosis; the impacts of partial degradation in the coaxial cable shielding or other shielded lines. At first, using classical transmission-line equations in the frequency domain, analytical expressions are derived to infer the impact of the very small discontinuities in transmission lines. Then, this paper illustrates the real experimental measurement cases of faulty shields on coaxial cable. The experimental studies of fault length effects are presented in frequency and time domain measurements by referring to a coaxial cable transmission line designed for high frequency signal transmission in aircraft radio communication systems. Finally, numerical simulation of the experimental case is presented and then validated against the measurement result by using a data processing technique based on time domain analysis.