The Developmentof Substation Fault Analysis System And The Study Of New Fault Location Method For Transmission Line

The current fault analysis system for power grids exists some shortcomings, such as the nonstandard of information access, the insufficient of information preprocessing, the low level of fault information integrative utility and so on. Therefore a new fault analysis system for substation based on the integration of fault recording and protection information is proposed in this article, which has the function of real-time fault analysis and off-line fault analysis to send brief fault report to the dispatch center and also the corresponding software is developed. It resolves the problem of format conversion between fault recording and protection information based on COMTRADE, does the information pretreatment using analog low-pass filter and digital filter. The integration of fault recording and protection of information uses the two different fault information for synthesized fault calculation and to judge the behavior of protection devices and circuit breakers.The analysis algorithms of fault analysis system for power grids are lack of efficiency and accuracy, so a new frequency monitoring and spectrum analysis algorithm is proposed after in-depth study of the various fault analysis algorithms.It can accurately calculate the amplitude, frequency and phasor of fundamental frequency component signal, integral harmonics and non-integral harmonics. Besides, the algorithm can also get the amplitude and decay time constant of the decaying DC component. The process of formula starts from the model of a single signal to get the amplitude, frequency and phase angle of single cosine signal, then extends to the general complicated signal, using Newton-Raphson to solve the equations. The algorithm has the advantages of higher accuracy and stronger real-time. Besides, the influence of spectrum analysis to different sampling point, different frequency of sampling and different rank is very small.The article combines different fault detectionalgorithms, fault phase selection methods and fault location algorithms.A new algorithm of calculating the fault location based on parameter detection using two-terminal system of electrical quantities is proposed in this article.The analytical expression of fault location derives from three-phase decoupling. The algorithm can calculate the synchronizing angle of two-terminal system and line parameters affected by the environment. It also overcome the drawbacks of the traditional fault location algorithms, which does not exist the pseudo-root problem. Besides it has the advantages of simple, practical, litter computation, no need to search and iterative and robustness. The algorithm has not influenced by fault types, the transition resistance and other factors.The practicability and validity of the improvements are verified by the result of a typical transmission line fault in a substation. It also meets the requirements of dispatcher personnel, protective personnel and operating personnel with variety of high accuracy algorithms.