Research Of Fault Transient Signals Based On Mathematical Morphology

With the rapid development of the power system capacity, and the substantial increase of large capacity units of HV transmission lines, the current situation puts forward higher requirement to power system protection. According to the requirements of the power system transient stability, the protection must act fast and reliably. The action speed of the relay protection based on fundamental frequency has reached the limit,. However, the protection with transient fault component acts quickly, which can satisfy the quickly action requirements of HV transmission lines. Limited by the shortage of signal analysis means, it is difficult to separate transient initial traveling-waves form varieties of noise interference, which restricts the development of the protection.When the transmission lines fault, the faulty points will produce high-frequency transient traveling-waves to the two bus lines, which contain wealthy information of the fault characteristics. On the basis of analyzing carefully the producing and spreading process of transmission lines traveling-waves, the thesis will apply mathematical morphology to the detection studies of transient traveling-waves fault characteristics. Then it proposes traveling-waves directional protection approach based on mathematical morphology. This approach uses multi-resolution algorithm of mathematical morphology to resolution the fault signal filtering, extract local features of transient initial traveling-waves and obtain the instantaneous power local maxima of traveling-waves signal. Then we can accurately determine the polar characteristics of the faulty mutation point and achieve the direction protection.The simulation for a simplified 500 kV line with Matlab/simulink indicates the reliability and validity of the protection algorithm. This algorithm is immunized to fault types, path resistances, fault time and so on. And it can reliably exclude noise and accurately determine the fault direction.