  This paper summarizes the electromagnetic time reversal (EMTR) technique for
fault location, and further numerically validates its effectiveness when the
fault impedance is negligible. In addition, a specific EMTR model considering
the fault impedance is derived, and the correctness of the model derivation is
verified by various calculation methods. Based on this, we found that when the
fault impedance is large, the existing EMTR methods might fail to accurately
locate the fault. We propose an EMTR method that improves the location effect
of high-impedance faults by injecting double-ended signals simultaneously.
Theoretical calculations show that this method can achieve accurate location
for high-impedance faults. To further illustrate the effectiveness, the
proposed method is compared with the existing EMTR methods and the most
commonly used traveling wave-based method using wavelet transform. The
simulation results show that the proposed double-ended EMTR method can
effectively locate high-impedance faults, and it is more robust against
synchronization errors compared to the traveling wave method. In addition, the
proposed method does not require the knowledge or the a priori guess of the
unknown fault impedance.
