Research On Ferroresonance Overvoltage In Distribution Networks

In the isolated neutral system, the excitation inductance is nonlinear. Overvoltage may occur once the excitation inductance becomes saturated, which seriously impacts the security of power system.Foreign and domestic exports have done many experiments and studies on ferroresonance. A great numble of suppressive measures have been proposed in the past decades. However, ferroresonance has not been entirely suppressed due to the complexity of nonlinear characteristics, flexibility of power system and constraints of measures. Therefore, it is necessary to study the suppressive measures in-depth.The paper establishes the simulation model of a substation in Zhejiang using ATP-EMTP and analyses the influence factors of ferroresonance overvoltage. Suppressive measures are alse simulated, including single-phase TV, nonlinear resistance, arc suppression coil, damping resistance, improving excitation characteristics and capacitor bank. All these measures studied in detail.Results show that it is effective to connect nonlinear resistance to the neutral point of the primary side of TV to suppress ferroresonance. Nonlinear resistance can restrain ferroresonance overvoltage rapidly and it functions in the whole network. Therefore, nonlinear resistance is better than 4TV method. The volt-ampere characteristics of nonlinear resistance have great influence on the inhibition effet. However, the factor, a, does not influence the inhibition effet. In another way, nonlinear resistance and linear resistance have the same restrain ability of ferroresonance. Nonlinear resistance is recommended in consideration of its higher heat capacity. Arc suppression coil is also effective to restrain ferroresonance overvoltage but its transient process is so long. If the capacitive current of the system is large, arc suppression coil may become more useful. Furthermore, the paper analyses the theory and validity of other ferroresonance suppressive measures.