Study on Simulation of Ferroresonance Elimination in 10kV Power System

In the neutral node ungrounded power system, ferroresonance due to the matching of nonlinear excitation inductance of three-phase PT and network to earth capacitance once happened, has a serious impact on the safety operation of the power system. At present, some widely used prevention measures in practical engineering include: connecting a nonlinear resistance or connecting single-phase PT to the neural point of three-phase PT high voltage side. Some simulations on the two prevention measures are performed with the EMTP. Results show that disadvantages exist in the upper two methods when they are adopted separately. This paper presents a new combined prevention measure, i.e. a combination of single-phase PT and nonlinear resistance, which not only reduces transient current and over voltage but also reduces the zero sequence voltages during the original steady state or the resumed steady state after the disappearance of earth faults when nonlinear components are connected in the system. Therefore, the voltage relay can indicate earth faults exactly and the reliability of the system is increased