A locating system based on an advanced time difference of arrival (TDOA) estimation method is developed to locate the position of a discharge source to avoid pulsed electromagnetic interference (PEMI) with the surrounding radio communication environment. In general, from the waveforms of PEMI waves received by an antenna array, the source position can be located or the direction of arrival (DOA) of the EM waves can be estimated by applying TDOA-based methods. However, owing to noises and multipath waves that occur at the metal surfaces of electric power equipment, the estimation accuracy of the TDOA may decrease, and the location accuracy will be degraded. To improve the accuracy of TDOA estimation, we propose a new TDOA estimation technique. In our developed locating system, PEMI waves are received by a four-antenna-square array and the DOA is estimated from the TDOA, which is estimated using the generalized crosscorrelation phase transform method in combination with the proposed technique. A PEMI source is ultimately located by aiming a charge-coupled device camera, installed at the center of the antenna array, at the estimated DOA. The estimation accuracy of the locating system is evaluated through experimental measurements. The results show that the developed locating system can locate the position of a PEMI source existing within about 30 m from the system with high accuracy.Index Terms-Direction of arrival (DOA), localization, pulsed electromagnetic (EM) interference (PEMI), spark discharge, time difference of arrival (TDOA). 0018-9375

The operating voltages of low-voltage control circuits in power plants and substations have become lower owing to the installation of digital-control equipment. This significantly increases the risk of faults and malfunctions of such circuits due to abnormal voltages in the control circuits induced by lightning and switching surges. Therefore, the prediction of the induced voltages is strongly required for protecting such circuits from abnormal voltages.Recently, the FDTD (Finite Difference Time Domain) method, which solves Maxwell's equations numerically, is applied to the simulation of surge phenomena on conductors placed in three-dimensional arrangements such as transmission towers and buildings. The FDTD method can easily take into account the finite conductivity and relative permittivity of the ground soil and ground structure in detail. These parameters affect the induced voltages on control circuits.In this paper, first, we perform the FDTD calculations for a grounding grid whose size corresponds to a distributingsubstation area. Second, we calculate the potential rises of the grounding grid, currents flowing through the grounding grid, and induced voltages on a control wire above the grid. Comparing the calculated results with the measured ones, we confirm the applicability of the FDTD method to the calculation of the induced voltages on the control wire generated by current flowing into the grounding grid.

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