Research On Fault Location Of UHV Half-wavelength AC Transmission Lines

With the development of society,the inverse distribution of energy and load in the central and western regions of China has made the contradiction between them more and more serious.In order to solve this problem,the research on half-wavelength transmission lines has been paid more and more attention by experts and scholars.At present,most of the researches on half-wavelength transmission lines are focused on transient stability and so on.Few studies have been made on the accurate measurement of the fault location after a fault occurs.Most of the faults in high-voltage transmission lines are grounding faults,of which single-phase-to-earth faults are the most.This article analyzes the generation and transmission characteristics of traveling waves after a fault occurs,and studies the characteristics of the extracted traveling waves in the time and frequency domains.Due to the differences in voltage,current,and power characteristics of half-wavelength transmission lines and traditional transmission lines,the traditional traveling wave method has direct limitations on UHV half-wavelength transmission lines.Investigate the reducing of the traveling wave power when it travels on the half-wavelength transmission lines.The zero-mode traveling wave that rapidly decays to zero is no longer suitable for fault location methods.The energy of line-mode travelling wave on half-wavelength transmission lines gradually decreases,and the wave speed is no longer than the speed of light which is at the initial moment.This paper considers the use of changing line-mode traveling wave to accurately locate faults on half-wavelength transmission lines.By studying the relationship between the speed of the line-mode traveling wave on half-wavelength transmission lines and the location of the fault,the MATLAB simulation was used to fit it.After considering the calculation cost and the degree of fitting,the exponential function was selected to quantify the relationship.Take the wave velocity of the first and the end points on the line-mode traveling wave speed curve to calculate the fault location.After processing the average value of the fault location,a preliminary fault location result is obtained.The proposed method is improved from the optimization of line-mode traveling wave velocity and the recognition error compensation head of traveling wave.The improved method has greatly increased the positioning accuracy.Through simulation verification of different fault types,load sizes and ground resistances,the proposed method is more robust and adaptable.After the off-line preparation,the online positioning process is simple and fast.It not only has high positioning accuracy,but also has good robustness and applicability.It has great engineering application prospects.The thesis contains 47 figures,13 tables and 93 references.