Limitation of Internal Overvoltages in Insulated Neutral Networks with a Small Number of Connections

Single-phase ground faults are the most common type of failures in networks with an insulated neutral. For the power supply systems of mining enterprises, this is an emergency mode of operation and requires the faulty section to be disconnected. Using the example of a sparsely branched quarry network with an insulated neutral, the effectiveness of classical methods for control of overvoltages arising under the single-phase ground fault conditions is analyzed. The existing Russian regulatory framework specifying the requirements for the choice of electric network neutral operation mode is analyzed. It is shown that there is a need to develop a system criterion that would determine the neutral implementation method with taking into account the electrical system features and operation modes. Non-standard methods are proposed to reduce overvoltages on the electrical installation components, as well as the currents through the instrument voltage transformer windings to ensure their thermal withstand capability. Mathematical models in the MATLAB Simulink environment were used to evaluate the effectiveness of the proposed technical solutions. Recommendations are given on achieving more reliable operation of the ground fault relay protection and selecting the criterion for its operation in networks with a small number of connections. The waveforms of the characteristic modes for the original and improved circuit configurations are given.