Research On The Potential Distribution Characteristics Of Ultra-High Voltage Controllable Metal Oxide Arrester For Substation

With the development of China's ultra-high voltage(UHV)technology,the voltage level has been continuously increased.Therefore,power system overvoltage has become one of the decisive factors affecting the system's insulation level.Possessing good volt-second characteristics,UHV metal oxide arrester(MOA)can restrain the overvoltage of power system very well,and hence plays a significant role in maintaining safe operation of the system.Since UHV MOA withstands long-term steady state voltage or short-term system overvoltage during operation,the aging of its valves with relatively high voltage is accelerated and the safety of MOA operation threatened when the potential distribution of UHV MOA is uneven.The calculation and analysis of the potential distribution of UHV MOA may lay basis for monitoring MOA status and optimizing its structure.Based on the electromagnetic field theory and the finite element principle,this study established a three-dimensional model of UHV alternating current(AC)MOA and UHV AC switch type controllable metal oxide arrester(CMOA)using Ansoft Maxwell software,and performed a simulation calculation and analysis of the potential distribution of MOA.The UHV AC MOA model is applied to study the potential distribution of valve resistance when MOA is subjected to a steady-state voltage.The effects of voltage initial phase,short circuit and damp of valve plate,phase spacing and arrangement on the potential distribution are also analyzed based on the UHV AC MOA model.It is subsequently concluded that the steady-state potential distribution of UHV MOA tended to be uniform,but the voltage at the bottom section valve resistance is relatively high.Factors such as voltage initial phase,short circuit and damp of valve plate,phase spacing and arrangement shows the greatest influence on the potential distribution of the valve of the 1st and 5th unit sections of the MOA.The accuracy of the model is verified by comparing the simulation calculation results of steady-state potential distribution with existing experimental data.Following the verification of the model,the potential distribution of the valve resistance of UHV CMOA under steady-state voltage conditions,lightning overvoltage and switching surge are examined.The impacts on potential distribution by factors including short circuit and damp of valve plate,phase spacing and arrangement when CMOA is subjected to steady-state voltage or system overvoltage,are researched thereafter.The present study shows that the potential distribution of UHV CMOA is relatively uniform when it bore steady-state voltage,but the voltage at the end of the first section and the third section of the unit section are relatively high.Compared with UHV CMOA that bears overvoltage,the potential distribution of the valve slices of the CMOA bearing steady-state voltage is more vulnerable to effects exerted by factors such as short circuit and damp of valve plate,phase spacing and arrangement.