Influence of dispersion earth resistance variation on the consumers operation

Abstract

Associated phenomena usually to interruption of neutral conductor and to change of the dispersion earth resistance touch a sensitive aspect of low-voltage power networks. Therefore, a tool is needed to evaluate the risks associated with this behaviour. This paper proposes a mathematical model to describe realistic influence of dispersion earth resistance of earth electrode and unbalanced power supply system of the consumer, the phase currents and voltages on the consumer. These phenomena are directly related to the power quality and efficiency of protective system, especially in case of three-phase unbalanced consumers. In this paper it is shown that the neutral displacement voltage, neutral current and phase currents and voltages depend on the severity of the unbalance of three-phase consumer and of the value of three-phase dispersion earth resistance. Simulations are made for consumer operation in case of unbalanced regime with the dispersion earth resistance of earth electrode from downstream of fault location equal to 4 Ω, 2 Ω and 1 Ω. The results are useful for the design and operation of the protective system.