Research On Adaptive Reclosing Technology Of Transmission Lines

Compared with the traditional reclosing,the adaptive reclosing can identify the nature of the fault and detect the time of arc extinguishing,which can f undamentally eliminate the secondary impact caused by the blind superposition of permanent fault in the traditional automatic recloser in a short time.In this paper,based on the existing reclosing theory and method,the single-phase adaptive reclosing method and the three-phase adaptive reclosing method are studied in this paper.This paper analyzes the dynamic characteristics of fault arc and the terminal voltage when single-phase reclosing and three-phase reclosing are adopted in the transmission line,and establishes the fault simulation model of single-phase reclosing and three-phase reclosing by using ATP/EMTP software.A single-phase adaptive reclosing method based on wavelet packet energy i s proposed.Firstly,the frequency characteristics of trans mission lines with transient and permanent faults are analyzed.The characteristic frequency band of fault phase voltage is extracted by wavelet packet analysis and the content of harmonics and interharmonics is calculated by wavelet packet decomposition co efficient.The threshold value is determined according to the content of harmonics and interharmonics in normal operation of the line.When the content of harmonics and interharmonics in fault phase voltage is larger than the threshold value and the total energy rises,it is identified as a transient fault.Finally,after the transient f ault is determined,the fault arc quenching is judged according to the content of harmonics and interharmonics in the recovery voltage stage which decreases sharply to less than the threshold value.The method is simple to set the threshold value,and the simulation results show that the method can effectively identify the fault nature and judge the extinction time.A three-phase adaptive reclosing method based on Prony algorithm is proposed.First of all,the paper analyzes the transmission line fails and paralleling reactance after three phase tripping current frequency characteristic: single phase or two phase ground fault occurs,for permanent or arc fault,instantaneity paralleling reactance only contains a free oscillation component fault phase current,if has arc fault,instantaneity paralleling reactance each phase current contains two similar free oscillation frequency component,considering the line resistance effect,can be expressed as a linear combination of the two attenuation periodic components.Then,Prony algorithm is used to estimate the parameters of shunt reactance current by using the characteristics of high resolution and accurate fitting of attenuation periodic component and combining w ith singular value decomposition to determine the effective order of the signal.Finally,the line parameters are used to determine the frequency range of the line oscillation,and the self-adaptive reclose is realized by detecting the number of frequency c omponents within the frequency range in the Prony analysis results.The recloser scheme is based on the free oscillating component of shunt reactance current.The frequency will not change with the decrease of current amplitude.Simulation results show that the proposed method can effectively identify fault properties under different fault locations and transition resistances.