Characteristics Analysis Of Very Fast Transient Overvoltageand Its Numerical Simulation Study

With the development of EHV and UHV transmission technology, Gas Insulated Switchgear (GIS) has been used widely.In routine operation, the disconnectors in Gas Insulated Switchgear (GIS) will produce a large amplitude, high frequency, short front time Very Fast Transient Overvoltage (VFTO). It is easy to cause a series of electrical insulation breakdown, electromagnetic interference and other incidents, and it will cause great harm to the body of GIS, transformers and adjacent electrical equipment insulation safety.The study found that in 420kV and above voltage level of GIS, the very fast transient overvoltage has repeatedly cause malfunctions and other problems, resulting in losses. Therefore, the study of very fast transient overvoltage in EHV and UHV transmission system GIS has become an urgent problem.This paper studies the generated mechanism and characteristics of Very Fast Transient Overvoltage, including its magnitude, steepness and frequency. Focus on the residual charge, the entrance capacitance of transformers, the rise time of voltage, the branch length of GIS, the switching arc channel resistance and other factors on the Very Fast Transient Overvoltage.Exploring the protection measures of Very Fast Transient Over-voltage. Using the ATP-EMTP of electromagnetic transient program to simulate the waveform generated by Very Fast Transient Overvoltage and analyses the waveform. Then simulating the waveforms of Very Fast Transient Overvoltage after add protective measures by ATP-EMTP. We can find effective protective measures after contrast these waveforms. Thus, it will play a fundamental role about the suppression of Very Fast Transient Overvoltage in GIS.This article is focused on the Very Fast Transient Overvoltage generated in GIS in 1000kV UHV transmission system by EMTP simulating, and the harm of Very Fast Transient Overvoltage on the system caused. Which made effective protective measures, such as installing closing resistors, installing MOA, using a ferrite of magnetic ring,and so on. It also can provide important guiding significance for the insulation level, power systems’security, and economic and reliable operation in GIS and related equipment.