基于工频量极性比较的高压输电线路超高速方向元件

Ultra High Speed Directional Elements Based on Polarity Comparison of Power Frequency Components for High Voltage Transmission Lines

为解决现有方向元件动作速度和可靠性之间矛盾,提出一种基于工频量极性比较的方向元件。该元件通过小波变换提取故障前电压和故障电流的工频成分,利用两者之间的夹角表征极性关系,进而确定故障方向。该方向元件选用故障前的电压量判断故障方向,有效避免了电容式电压互感器(capacitor volatge transformer,CVT)暂态特性和小故障初始角对方向元件的影响。基于PSCAD/EMTDC的仿真结果表明,该元件能够快速可靠地确定故障方向,其性能不受故障初始角、过渡电阻、故障位置、故障类型、噪声、CVT传变特性和负荷状态的影响。

To solve the contradiction of operation speed and reliability of the directional element of present protections, a novel directional element was proposed based on polarity comparison of power frequency components in this paper. The power frequency components of the pre-fault voltage and the fault current were extracted based on wavelet transform. Then the polarity relationship between power frequency components of the pre-fault voltage and the fault current was described by the angle between them. Thus, the fault direction can be determined. Since the proposed directional element utilizes the pre-fault voltage to determine the fault direction, it avoids the influences of the transient characteristic of capacitor voltage transformers （CVTs） and small fault inception angles on direction elements. The simulation results based on PSCAD/ EMTDC indicate that the proposed directional element is able to determine the fault direction rapidly and reliably and its performance is insensitive to fault inception angles, fault resistances, fault positions, fault types, noise, CVT transfer characteristic and load conditions.