Determining the efficiency of the compensation of single-phase capacitive earth currents using arc-suppression coils of different designs implemented in an experimental workbench

Abstract

Results of the experimental comparison of the compensation of single-phase capacitive earth currents using arc-suppression coils of two cardinally different designs, i.e., plunger-type coils and coils controlled by magnetic bias, are presented. It was previously shown using the simple formula and the calculation grid model that the response time of the reactors determined through the time required to compensate the power component of the earth current depended on the phase angle of the voltage at the moment of earth fault [1]. If the earth fault occurs not at the moment of the maximum voltage, an aperiodic component appears in the coil current, which makes it impossible to compensate instantaneously the capacitive earth current. An experimental workbench with a voltage of 6 kV used to carry out the measurements is described. The measurement results show that the coils of both designs have similar response times, which are on average of the order of a few hundreds of milliseconds; these values substantially exceed the implied values of the response time of the coils. It is shown that the response time of the coils cannot be the criterion for their efficient operation. Therefore, to compensate for an intermittent arc capacitive earth fault, a comparative criterion for assessing the efficiency of the operation of the coil is proposed, which is based on the average value of the energy dissipated the site of fault.