基于暂态能量的输电线路速动保护方案

利用母线杂散电容吸收高频分量的特点,构成了能准确区分区内、区外故障的速动保护方案。对输电线路保护安装处的电压、电流进行模量转换得到模量电压和模量电流,并将模量电压和电流进行Daubechies 4小波变换得到所需频段的低频信息和高频信息,利用这些信息计算得到相应频段的频谱能量,然后得到模量电压和模量电流的暂态特征,将电压和电流的暂态特征综合起来得到故障后的暂态能量,该暂态能量可用来识别故障位置。该保护方案的灵敏度不受过渡电阻、雷击、故障类型、负荷电流、系统运行方式等因素的影响。此外,由于保护的数据窗很短,电压互感器、电流互感器的传变特性对保护的性能没有影响。

A Transient Energy Based Fast Protection Scheme for Transmission Lines

Using the phenomenon that the stray capacitance in busbar can absorb high frequency components in fault signal, a fast protection scheme that can distinguish internal fault from external fault is constructed. In the proposed scheme, on the basis of the modulus conversion of current and voltage at the position of protection device, the low frequency information and high frequency information of the needed frequency band are gained by means of transformation by Db4 wavelet. The spectrum energy of corresponding frequency band can be calculated to obtain the transient characteristics of modulus current and modulus voltage, which can be combined to calculate the post-fault transient energy. The calculated transient energy can be used to recognize the faulty position of transmission line. The sensitivity of the proposed protection scheme is not impacted by the factors such as transition resistance, lightning stroke, fault type, load current and operating mode of power system. Besides, the data window of the proposed protection scheme is short, so its performance is not affected by the transferring and transforming characteristics of CT and PT.