Study On Secondary Arc Characteristics And Control Technology For UHV Half-wavelength Transmission Lines

Electric power industry is a basic industry related to the national economy and people,s livelihood.In order to meet the energy demand in the development of eastern and central regions of China,large-capacity and long-distance transmission technology is an inevitable choice to optimize the allocation of energy resources and promote the development of national economy.The transmission distance of AC half-wavelength transmission technology can reach 3000km,which has the advantages of small equivalent impedance,no reactive power compensation and good voltage stability.However,the key problems in the development of AC half-wavelength transmission technology are still not perfect.The suppression of secondary arc in single-phase reclosure process is one of the key problems to be solved urgently in the development process.Aiming at the problem of secondary arc of half-wavelength line,combined with relevant research results,this dissertation introduced the generation mechanism of half-wavelength line's secondary arc in time domain and frequency domain.Referring to Zhundong-Central China power grid,a simulation model of half-wavelength transmission system and its secondary arc is built for UHV transmission project.The characteristics of secondary current and recovery voltage during single-phase grounding of UHV half-wavelength transmission line and their influencing factors are analyzed.In this dissertation,the suppression principle,effect and scheme of high-speed grounding switch are studied.In the case where 11 sets of high-speed grounding switches are evenly arranged along the half-wavelength line,the amplitude of the secondary current and the recovery voltage can be limited to "80A,10kVH by n 1200A,452.2kVn with a reasonable action strategy.However,the level of induced current and voltage in the opening and closing process of high-speed grounding switches is far beyond the current domestic test range,and the tolerance of the equipment needs further test and verification;besides,the number of switches along the line is huge,and the coordinated and effective action of multiple groups of switches brings great challenges to the protection device.In view of the shortcomings of the high-speed grounding switch suppression measures,this dissertation studies the high-resistance and neutral-point small reactor and controllable compensation methods.The former is the cormon method of China's UHV conventional transmission lines,the latter is a new way to suppress the secondary arc.This dissertation presents a controllable compensation method based on the characteristics of secondary current at different fault points along half-wavelength line.Two different strategies of compensation at the first end of fault phase and compensation at both ends of fault phase are adopted.The a.plitude of secondary current and recovery voltage can be limited to "17A,lOkV".Then the specific topology and implementation scheme of controllable compensation power supply are studied.The suppression effect is very obvious and the logic of action is simple.The secondary arc characteristics and control technology of UHV half-wavelength transmission lines studied in this dissertation are studied as part of the State Grid Corporation's scientific and technological project "Research on AC Transient Characteristics and Control Measures of AC Half-Wavelength Transmission,.The suppression method,in which the controllable compensation method is a new research idea,can make up for the deficiencies of the conventional suppression methods.