Control of resistive neutral grounding based on the smart grid principles

Shifting medium-voltage networks to operate with the neutral grounded via a resistor or an RL circuit is the most promising approach to improving the reliability of electric power supply systems either with or without capacitive current compensating devices. The Smart Grid principles imply minimization of losses to consumers; therefore, the optimal solution for the neutral grounding mode can be reached only with automatically controlled grounding devices. The article is devoted to studying and elaborating algorithms and circuit arrangements for control of the resistor taking into consideration the entire set of conditions and requirements imposed on the characteristics of particular electric networks. The results obtained from simulation of transients triggered by ground faults for a range of initial conditions and network parameters are presented, and the optimal values of active currents, at which an arcing fault unconditionally transfers into a stable mode, are determined. Algorithms are suggested; and circuit arrangements of devices are developed to control the resistor installed in the neutral of compensated and non-compensated networks.