| Since the beginning of the 21st century,the whole society's demand for electric power resource has increased rapidly with the development of Chinese economy.The Ultra High Voltage(UHV)transmission technology has been unsuitable to meet the growing demand for electric power.Ultra High Voltage Direct Current(UHVDC)transmission technology has become an important measure to alleviate the imbalance of energy distribution and economic development in China because of its economy in long-distance and large-capacity power transmission.During the peak period of power consumption in summer,the extra-high voltage line will easy to run at full capacity.If there is an unplanned shutdown,it will threaten the safe and stable operation of the power grid and cause great losses to the national economy.The live working of the UHVDC transmission line is a guarantee to ensure its stable operation.Due to the complicated working environment of live operation of UHV transmission lines,the intensity of electric field in the live working gap will be higher and the risk of live working will be higher too.In order to ensure the safety of live working,it is necessary to study and put forward appropriate safety protection measures for workers.In view of the high voltage grade of UHVDC transmission line and the transfer between the complex environment characteristics of potential transfer,this paper proposed an analysis model of discharging process for potential transfer.In order to provide feasible reference to perfect development of live working of UHV transmission lines,the air gap discharge phenomenon of potential transfer for UHVDC transmission lines is researched,and the characteristics of the propogation of discharge process and its influence on live working safety protection are analyzed.Firstly,the characteristics of discharge process of potential transfer in live working are analyzed.Then,according to the theory of fluid dynamics and gas discharge,the mathematical governing equation of discharge is determined,and the simulation model is built by COMSOL Multiphysics.In the end,the development characteristics of gap discharge are obtained,the variation characteristics of electric field intensity,current density and energy during discharge development are analyzed,the influence of different length of transfer distance on streamer development,discharge current,energy and other parameters are discussed,and the appropriate protective measures in the process of potential transfer are proposed.The results show that the gap discharge of potential transfer develops rapidly and the electric field intensity of gap electric field changes rapidly.The discharge process is directly related to the length of transfer distance.Under different length of transfer distances,the electric field intensity,discharge current density and energy are different.The longer the transfer distance is,the faster the discharge development rate is,and the higher the transfer energy is.Energy transfer is easily higher than the recommended safety threshold,and operators should adopt potential transfer rod for transfer. |
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