The Research Of Ferroresonance Overvoltage In 35kV Distribution Network

In the medium voltage distribution network system, grounding and breakdown fault are more likely to be found due to the large-scale use of isolated neutral-point operation pattern and the distribution of transmission lines in the densely populated urban and rural areas. The electromagnetic voltage transformers are widely used in distribution lines, and the nonlinear characteristic of the excitation inductance can cause the excitation saturation consequently lead to resonant overvoltage when a fault happens. Ferromagnetic resonance overvoltage often occurs in medium voltage distribution network, which significantly affects the safe and stable operation of the distribution network. Thus, it is necessary to study and simulate the ferromagnetic resonance overvoltage, and to improve the measures of resonance elimination.This paper does a large number of research in simulation model of a 110/35kV substation with the usage of ATP-EMTP through simulating a variety of fault modes caused by ferromagnetic resonance. With the connection of least square method and the mathematical mode of voltage transformer excitation inductance established by using Basic Visual 6.0 software, the excitation characteristic curve of the voltage transformer is obtained. Through the simulation, the voltage waveforms of the 35kV isolated neutral-point are obtained under different fault modes.After the analysis of the simulation results of ferromagnetic resonance overvoltage, the paper simulates the common measures of resonance elimination, discuss their advantages and disadvantages, and proposes a combination methods of resonance elimination. Compared with the combination measures and the traditional measures of resonance elimination by ATP-EMTP simulation, the simulation voltage waveform shows that the new measures are better. Meanwhile, there are also a lot of problems of new measures, which need a more in-deep study.