Research On EHV Transmission Line Transient-based Protection Scheme Based On Prony Algorithm

The study of transient-based protection is very important for improving the performance of existing protection. This paper presents a transient-based protection scheme based on fault transient current signals.Firstly, the current transient signal components under distributed parameter are analyzed using operation method when different fault types happen. Analysis results show that the fault transient signals contain harmonic high frequency components. Further theoretical analysis shows that, the amplitude and frequency of high frequency components can distinguish between various fault types. This paper defines the maximum amplitude of the high frequency transient components as"Dominant Harmonic Frequencies". Theoretical analysis shows that, the frequency and phase of high frequency components can distinguish between internal and external faults. That is, when external faults happen,"Dominant Harmonic Frequencies"has the characteristics of"the same frequency and the same phase"; when internal faults happen,"Dominant Harmonic Frequencies"does not have the characteristics.In this paper, different kinds of Prony algorithms are summarized and compared, and the Prony algorithms is improved in two aspects: first, the computing efficiency of the algorithm, the other, the reliability of the algorithm. By using backward linear prediction, the improved algorithm has higher noise immunity, and the problem of false frequency components caused by noise was solved. By using the QR decomposition algorithm, the computation time of the improved algorithm is significantly reduced than traditional algorithms. In order to extract the true frequency more reliable a method based on energy was proposed. This paper gived a complete algorithm based on above aspects. In order to make Prony algorithm more suitable for this subject, the parameter selection method was analyzed and summarized in detail.The complete faulty phase selection and protection scheme were proposed. The reliability has been analyzed when series capacitor and shunt reactor are installed, as well as lightning interference. In this paper, characteristics of lightning interference were analyzed and the identification scheme was proposed. Various fault scenarios have been simulated by ATP. The simulation results show that the proposed scheme is capable of providing fast and correct responses under conditions of different fault types, path resistances, inception angles and lightning interference, as well as additional transient signal generated by series capacitor and shunt reactor.