Analysis And Research Of Frequency Characteristics Of EHV Transmission Line Transient Protection Based On ESPRIT Algorithm

With the continuous development of national economy and the expansion of scale of the power system, the stability of power grid operation is being challenged, while users are increasingly demanding on the stability of power system. In order to improve the stability of the transmission line transient process and transmission line power transmission ability, Split conductor is widely used in the process of extra-high voltage (EHV) power transmission, which often hold capacitor in series and parallel reactor, that led to the failure of transient process is very obvious. In order to guarantee the reliability of the action, the traditional power frequency protection usually adopt the method of filtering or delayed to eliminate the negative impact of the transient process, but it will extend protection action time. In view of the deficiencies of the traditional protecting application in EHV, exploring new protection principle action fast and reliable is a difficult and hot issue in today’s power system research.The causes of the fault signal transient frequency component is analyzed in theoretical and the various types of fault transient frequency and amplitude is analyzed in detail. The influence of different transition resistance, shunt reactors etc to transient frequency are discussed in detail in this paper. Characteristics of transmission line transient frequency component can accurately distinguish the different fault types are demonstrated on theoretically. Frequency interval tends to be stable when frequency component is gradually increasing which is obtained by the simulation. On this basis, the distance to the point of failure to the source was deduced, and the distance provides the judgment basis for the fault inside and outside in the area.To frequency feature extraction of transient signal, the widely applied FFT, Prony and MUSIC algorithm are analyzed in this paper. Aimed at the deficiency existing in these algorithms, ESPRIT algorithm is mainly studied. The influence of SNR, arrays and snapshots to the performance of the ESPRIT algorithm is discussed by simulation. Through analysis and comparison, ESPRIT algorithm is much more rapidity, accuracy and reliability. The phase selection scheme and the protection scheme are structured by fault signal frequency and transient frequency interval. The impact of lightning interference to transmission line was studied in detail. According to characteristics of lightning interference, the more complete phase selection scheme and the protection scheme are proposed.A lot of simulation experiments about different fault types, fault locations, fault time and lightning interference have been done by EMTP-ATP, and the fault data is imported to MATLAB with ESPRIT algorithm analysis. Results show that the phase selection scheme can reliably and quickly judge the fault line and the protection scheme can reliably and quickly determine the area of failure.