Study On Dielectric Breakdown Characteristics Of Typical Defect Oil Paper Under AC/DC Superposition

In order to ensure the safe and stable operation of the power system,a large number of large dry-type air core reactors will be applied to the transmission lines of the power grid.The shunt reactors are used for reactive power compensation,and the series reactors mainly suppress high-order harmonics and limit the inrush current.However,a certain overvoltage occurs during the process of inputting and cutting off the reactor,causing the device itself to malfunction.Therefore,it is necessary to simulate and analyze the voltage of the shunt reactor and the series reactor.Because the simulation analysis of the overall parameters of the reactor can not reflect the internal electromagnetic process,this paper focuses on the investment and cutting of the distribution parameters of the reactor.The voltage is subjected to detailed simulation analysis and simulation studies on overvoltage protection.Before the reactor overvoltage simulation,it is necessary to accurately calculate the distribution parameters and overall parameters of the two reactors.When calculating the distribution parameters,each envelope of the four envelopes is equivalent to ten parts.The Barty transform method is used to calculate the inductance matrix.The mirror method and the analog charge method are used to calculate the capacitance of the inner envelope.The application of Maxwell The simulation calculates the interturn capacitance.Then all the distribution parameters are equivalent to a whole,that is,the overall parameters of the reactor.According to the principle that the vacuum circuit breaker throws and cuts the reactor to generate overvoltage,when the overvoltage simulation is input,it is divided into zero voltage closing and peak voltage closing;when the overvoltage simulation is cut off,it is divided into 10 A intercepting and opening.And zero current tripping.In this paper,the overall parameters and distribution parameters of shunt reactors and series reactors are analyzed in detail.The amplitude,frequency and decay oscillation time of each part of the distributed parameters are considered..In addition,several kinds of protection methods of the reactor are simulated and analyzed,and the amplitude variation and frequency variation of the overvoltage are compared.An optimal protection mode is selected for the shunt reactor and the series reactor.The simulation results of the over-voltage and the over-voltage calculation of the reactor's overall parameters and distribution parameters show that the shunt reactor will generate over-voltage when the peak voltage is closed and the 10 A cut-off is opened.The series reactor will be in the case of four kinds of opening and closing.An overvoltage is generated.When the reactor is closed,the overvoltage value of the first end is too large,which can reach twice the end overvoltage value;when the reactor is opened,the multiple of the overvoltage generated by each part is basically the same,but the oscillation frequency of the first end Partially large.A simulation study of the overvoltage protection of the reactor is available.The effective combination of the arrester and the RC protector provides the best protection for the reactor,which can reduce the overvoltage multiple and reduce the decay oscillation time.In order to achieve better protection effect,the arrester and the RC protector are simultaneously connected in parallel at the beginning and the end of the shunt reactor,and the arrester and the RC protector are simultaneously connected in parallel between the head end of the series reactor and the ground.