|
Transmission line fault will not only reduce the reliability of the power grid, will seriously affect the safe and stable operation of the power grid, resulting in significant losses. Transmission line is shorted to ground, the voltage near the point of failure is a sharp decline in the current increases rapidly, obvious failure the conventional protection capable of reliable detection and treatment; high impedance transmission line ground fault, transition resistance, causing the voltage a small amount of current mutation, failure unclear, thus increasing the difficulty of detection, conventional protection may not be the correct action. With the continuous expansion of the modern grid scale, fast fault detection, higher demands, therefore, to explore the detection of new programs, quickly identify and eliminate the high impedance fault has important research value. Wavelet transform has good time-frequency localization ability, able to detect a weak signal changes; traveling wave protection can be ultra-high-speed action, less susceptible to system operation mode oscillation, current transformer saturation impact of anti transition resistance ability, suitable for The detection of high impedance faults. Based on the traveling wave theory, using wavelet analysis, the proposed new program of high impedance ground fault detection of a high voltage transmission lines. Wavelet transform to extract fault current wave, by comparing the voltage, current initial traveling wave modulus maxima polarity relationship, the distinction between the positive and negative direction of the fault; initial wave head time scale by comparing the same or different scale initial wave head of the ratio of the time, the failure to identify the positive direction of the district, district. The theoretical analysis of ATP simulation results show that the method is not only quick to respond, and almost independent of the fault location, fault type, fault initial phase angle and the impact of the transition resistance, capable of rapid, sensitive and selective detection of high impedance ground fault. Paper a detailed analysis of the transmission line lightning directly stroke, lightning and single-phase ground fault line wave size and waveform comparison line mode component and ground mode component ratio, spike and wave tail ratio of the maximum steepness and comparison occurs before and after lightning current changes in the amount of the difference, distinction between the nature lightning (lightning, light lightning directly stroke) of the non-fault and fault (heavy lightning directly stroke), single-phase ground fault. Exclude the effects of lightning interference, improve the reliability of the high impedance ground fault detection. Finally, a summary of the research, the problems of research and directions for further research.
|