Generation Technology Of Non-Standard Lightning Impulse Voltage And Study On The Breakdown Characteristics Of Oil Dielectric Under Its Action

In order to ensure the safe operation of the whole high-voltage power system,the primary and secondary equipment in the substation must be stable.However,these power equipments will suffer many lightning shocks in the process of daily operation,which seriously threatens the safety of the whole power system.The research shows that the actual lightning impulse voltage in the substation is mostly non-standard lightning impulse voltage,which is affected by complex equipment lines and resonance in the substation,so that the actual lightning impulse voltage suffered by the substation is quite different from the standard lightning impulse voltage（1.2/50μs）used in high-voltage equipment withstand voltage test.In order to further discuss the difference between the high-voltage equipment in the substation when it bears the non-standard lightning impulse voltage and the standard lightning impulse voltage（1.2/50μs）,and reduce the manufacturing cost of the equipment as much as possible under the condition of ensuring the reliable insulation of the equipment,this paper mainly studies the actual non-standard lightning impulse voltage of the insulating dielectrics（transformer oil,capacitor oil,oil film）commonly seen in the three kinds of equipment Compared with the insulation characteristics under the standard lightning impulse voltage,it not only helps to determine the insulation specifications of high-voltage equipment,reduce the cost of equipment,but also provides technical support and theoretical basis for lightning protection in substation.Firstly,the breakdown characteristics of transformer oil,capacitor oil and oil film dielectrics were studied under the standard lightning impulse voltage（1.2/50μs）.In this paper,the 50%breakdown voltage(U₅₀)and V-T characteristic curves of several dielectrics under standard lightning impulse voltage are obtained.The results show that under the standard lightning impulse voltage,there are obvious differences in U₅₀ and V-T characteristics between different dielectrics.Secondly,according to the significant characteristics of non-standard lightning impulse voltage waveform,this paper aims to develop a circuit that can generate non-standard lightning impulse voltage.Firstly,the circuit simulation is carried out through Simulink,and then the device that can generate non-standard lightning impulse voltage waveform is designed according to the simulation circuit.The research results show that the test platform designed in this paper can produce the non-standard lightning impulse voltage with expected attenuation of high-frequency oscillation,and the impulse voltage waveform measured by the actual circuit is basically consistent with the voltage waveform generated by the simulation circuit.This study lays a foundation for further study of dielectric breakdown characteristics under the action of non-standard lightning oscillation impulse voltage.Finally,the breakdown characteristics of several dielectrics such as transformer oil,capacitor oil and oil film are studied under the non-standard lightning surge voltage.In this paper,the characteristic curves of 50%breakdown voltage U₅₀ and V-T of several dielectrics under the non-standard lightning surge voltage are obtained.Under the same conditions,the differences between the characteristic curves of U₅₀ and V-T of several dielectrics under the standard lightning surge voltage and the non-standard lightning surge voltage are compared and studied.By changing the waveform parameters（wave front time,wave tail time,Oscillation frequency）to explore the breakdown characteristics of transformer oil,capacitor oil and oil film dielectrics when the waveform parameters are different.The results show that the 50%breakdown voltage of transformer oil,capacitor oil and oil film dielectrics under the non-standard lightning impulse voltage is higher than the 50%breakdown voltage under the standard lightning impulse voltage（1.2/50μs）.When the waveform parameters of non-standard lightning impulse voltage change,U₅₀ of these dielectrics will also change.When the wave front time is longer or the oscillation frequency is higher,the U₅₀ of the dielectrics will be larger.