Research On Protection Method Of UHVDC Transmission Line

In the environment where my country’s energy resource distribution and supply-demand relationship are seriously mismatched,Ultra High Voltage Direct Current(UHVDC)has attracted much attention for its superior economy.However,due to the harsh natural conditions of the UHV DC transmission line and the long transmission span,the probability of failure and disturbance is high.In actual project operation,line faults account for more than half of the total number of faults,but the correct rate of line protection actions is not high.Therefore,studying the protection methods of UHV DC transmission lines is of great significance to improving the stability of power transmission.The thesis takes Yunguang ±800k V UHVDC transmission line as the research object.First,the Yunguang ±800k V UHVDC transmission line is introduced.And based on the actual parameters of Yunnan-Guangzhou UHVDC transmission line,the mathematical model of the line is built under the PSCAD/EMTDC simulation software environment.Secondly,by setting up faults in different conditions in the line area,outside the area,and at the positive and negative poles,the fault information is extracted from the total,and the fault characteristics of different frequency bands of the fault information and the difference of the additional network after the fault are analyzed respectively,and the wavelet transform is proposed.UHVDC traveling wave protection and UHVDC pilot protection based on branch current characteristics,using MATLAB to realize the protection algorithm to effectively verify the protection scheme in this paper.Thirdly,in order to reduce the impact of lightning interference on the stability of line protection,a protection method against lightning interference is proposed by studying the energy spectrum under different lightning strikes,which supplements traveling wave protection and pilot protection,and further improves The stability of the line protection is improved.Finally,summarize and prospect the content of the paper.Traveling wave protection is the main protection,and the longitudinal protection is the backup protection supplemented by lightning protection.In a complementary way,the problems of weak resistance to high resistance and anti-interference ability of traveling wave protection and slow response speed of longitudinal protection are solved.