The System Design Of Wave Transmission Line Fault Location Based On NIOS Ⅱ

Long distance powered transmission lines are often hundreds of kilometers long, the work environment of transmission lines is very poor, as a result that the most of power system fault happened at conductors. The traditional method of locating the fault is to analyze the accidents recorded wave data, the integrated power outage information, and then forecast the likely point of fault. Worker would be sent to confirm the information. This method is time-consuming and inefficient. Or using impedance protection device to measurethe impedence between the point of the short circuit point and the point of the installation of the device, and then compare the impedance with the same line length to get the fault distance.But by the transition fault resistance, short circuit arc resistance voltage measurements, the accuracy is not high. Therefore, the study of high-precision transmission line fault location has great significance.This paper analyzes that if the transmission line failure have happened, fault transient traveling wave will spread to the line at both ends. It has discussed the advantages and disadvantages of the various ways based on transient traveling wave fault location and suitability, and choosed the method of locating the point of fault through transient traveling wave based on GPS in the design. The receiving devices are installed at both ends of lines to record to the traveling-wave arrival time, and get the result of time difference to calculate the precise location. The method is accurate and not affected by the system operation mode, the theoretical error is less than 30m. Taking into account that the distortion of wave would cause the first arrival time error of transient traveling wave, the method of wavelet transform was used to analyse the acquisition of the traveling wave data. and fast Mallat wavelet transform was used to distinguish the maximum absolute value of the wave data to determine the first wave arrival time and reduce the positioning error.Meanwhile, devices were designed to collect and measure the transient traveling waveform data in this paper. Using a combination of FPGA and SDRAM technology to design the soft core of NIOS II soft core. The devices has contained these parts, such as traveling-wave signal acquisition,signal processing and amplifying, AD data acquisition, GPS synchronized positioning and precise timing, logic processing, multiple low-level processing,the communication module,and so on.The interface program was writen with the technology of MALTAB GUI. At the end, the data was decomposed there times by the Db4 Wavelet through MALTAB, and using the third layer of high-frequency coefficients of the discriminant of the maximum absolute value of the wave data to get the arrival time of traveling wave head.