Research on accuracy of electrical energy measurement in microgrid for mine dewatering

Abstract

The object of the study is the current transformers of the electricity metering unit as part of the microgrid for mine dewatering, which includes a photovoltaic station. The need to pump mine waters is caused by the danger of flooding large areas. The introduction of a photovoltaic station to power underground pumps reduces electricity consumption from the central power grid. At the same time, it changes the operating conditions of the metering unit. There is a need to measure both the currents of the pumps in the absence of solar generation, as well as relatively small current flows in the case of commensurate capacities generated and consumed within the microgrid. A feature of electromagnetic current transformers is a decrease in the accuracy of operation if the primary current is several percent of the rated value. Based on the analysis of variance of the experimental data, it was established that there is a statistically significant connection between the secondary and primary currents of the measuring transformer at insignificant values of the primary current. Estimates of the values of the linear regression parameters that link the secondary and primary currents were determined. It was established that in the range of the transformer primary current from 0.22 % to 1.4 %, the current error reaches a value of 6.7 %. Taking into account the resulting dependence in the software of the electricity metering unit will make it possible to increase the accuracy of energy metering. Accordingly, the accuracy of financial calculations will be increased