Measurement of switching transient overvoltages with a capacitive electric field sensor

Abstract

This paper presents a case study of measurements of switching transient overvoltages using a capacitive electric field sensor. The system was developed and installed in a substation after the failure of a surge arrester during the energization of a 420 kV transmission line. First, the closing operation was simulated in an electromagnetic transient simulation program to estimate the switching transient overvoltages for this event. Then, the concept and design of the measurement system are explained. The system calibration performed in the high-voltage laboratory is presented. Afterward, the installation of the measurement system in the substation is discussed, with a special focus on the calibration of the voltage ratio considering the physical configuration where it is installed. Finally, the measurement results are presented and compared with simulations. The results show that the transient overvoltages caused by the energization of the transmission line should not cause the failure of the surge arrester. The measurement system has been demonstrated to be capable of measuring switching transient voltages of a 420 kV transmission line and can be considered a flexible solution for the long-term monitoring of transient overvoltages in substations.