Technical Solutions for Preventing the Development of Single-Phase Ground Faults and for Eliminating Them in 6–10 kV Power Plant Switchgears

Abstract

The severity of the consequences from single-phase ground faults (SPGF) at the combined heat and power plants (CHPPs) operating as branches of PJSC Mosenergo is due to the following two main reasons: prolonged exposure to overvoltage and a significant wear of primary electrical equipment. The operation mode with a compensated neutral assumes setting up conditions for arc self-extinguishing at the SPGF location; however, in the majority of cases this does not happen. The practice of continuing the operation with an SPGF for several hours has a negative impact on the power plant electrical equipment and needs to be revised. To evaluate the influence of an SPGF in a 10 kV network on the reliability of power plant operation, the main electrical connection circuits and the adjacent network at 12 CHPP branches of the Mosenergo company is analyzed. The basic technical solutions aimed at preventing the development of and eliminating SPGFs in the 6–10 kV CHPP network are considered. In carrying out the analysis, the overvoltage modeling results were used with taking into account the feasibility of implementing various solutions at power plants. Based on the analysis results, the possible technical solutions have been divided into more and less efficient ones. For the majority of CHPPs, an efficient solution implies the transition from the compensated neutral grounding mode with holding an SPGF for a long period of time to low-impedance resistive neutral grounding with clearing the fault by the action of relay protection and automatic control devices