Research On Submerged Supply Current Suppression And Reclosing Strategies For Half-wavelength Transmission Lines

In order to overcome natural obstacles,people are constantly looking for more effective and lower-cost alternative solutions in the case of long-distance transmission.Halfwavelength technology for point-to-point power transmission(i.e.a length of 3000 km at 50Hz)is technically and economically suitable for long-distance power transmission.Because it does not need reactive power compensation,the investments of half-wavelength transmission line are lower that of traditional AC transmission line which uses capacitor and inductor reactive power compensation.In view of China's huge territory and energy distribution,the development of half-wavelength transmission technology is of great significance.For half-wave line,malfunction or a lightning strike is inevitable,but most of the malfunction occurred in the power system is a single-phase grounding fault of instantaneity.With the assistance of a recloser,the malfunction can quickly be cut off.After malfunction disappearance,the circuit runs normally.Because the voltage of half-wavelength lines is 1000 KV,even if the circuit is broken,malfunction points can generate arc that can continue to burn.And the fire is difficult to put out,in other words,it is great harm for reclosers.Therefore,suppression measures for secondary arc current are necessary.These measures are studied in this paper.At first,this research analyzes the steady-state traits of the half-wavelength circuit.Considering the limitation of geographical conditions,manual compensation is required for the circuit and a tuned half-wavelength circuit is built.The characteristics of the halfwavelength circuit cannot be changed after tuning.Secondly,this research analyzes the features of voltage and current distribution of natural half-wavelength and tuned halfwavelength line;the diverse influences of load capacity and power factor,current and line loss rate along the line are obtained.Thirdly,this paper analyzes the reason why the secondary arc current and recovery voltage of half-wavelength line are different from those of short distance line,the distribution characteristics of secondary arc current and recovery voltage of half-wavelength line,and the influence of different factors on secondary arc currents and recovery voltages of half-wavelength lines,as well as the distribution characteristics of secondary arc currents and recovery voltages of tuned half-wavelength lines with different tuning distances.Fourthly,by analyzing the principle of suppressing secondary arc current with High Speed Grounding Switch(HSGS),it is concluded that the reason of suppressing secondary arc current with HSGS in half-wavelength transmission line;And how to configure HSGS to suppress the secondary arc current in the natural half-wavelength and tuned halfwavelength lines,and the measures to quickly suppress the secondary arc current and recovery voltage to ensure that the arc is quickly extinguished without reignition.In order to meet the requirements of reclosing,this paper proposes a configuration scheme of HSGS to suppress the secondary arc current for half-wavelength lines.Finally,by analyzing the characteristics of primary and secondary arcs and simulating primary and secondary arcs,this paper simulates the whole time of transient fault from primary arc to secondary arc until extinguishing and generating recovery voltage,and the changes of voltage at both ends of fault phase and permanent fault phase when different transient and permanent faults occur in half-wavelength transmission lines.By comparing the difference between instantaneous and permanent faults,the paper puts forward the method of distinguishing instantaneous and permanent faults in different stages,so that confirm the feasibility of half-wavelength line reclosers.