特高压半波长交流输电线路的行波保护

Travelling Wave Protection of UHV Half-wavelength AC Transmission Lines

中国的能源基地和负荷中心呈现逆向分布,负荷需求不断增加,能源输送问题成为关系国计民生的关键问题。特高压输电是解决中国能源输送问题的一种有效方案,因此研究特高压半波长交流输电具有重大意义。行波保护对于长线路、远距离输电具有其得天独厚的优势,根据半波长交流输电线路上的行波传播特征,提出适用于半波长交流输电线路的行波保护判据。针对半波长交流输电线路全线的保护,基于小波变换理论,选择3阶B样条函数构成小波函数的二进小波并作为主要小波方法,同时利用Mallat塔式分解算法构成保护的算法主体。在分析半波长交流输电线路模量频带空间特性以及小波函数系数序列幅频特性的基础上,确定保护的采样频率、小波变换尺度以及目标频带,并提出适用于半波长交流输电线路的纵联行波保护策略。利用PSCAD/EMTDC和MATLAB进行仿真和编程,由此得到的仿真结果验证了所提保护方案能够在各种故障类型以及故障条件下保护半波长交流输电线路全长和实现较为准确的故障测距,且具有良好的抗过渡电阻的能力。

The energy bases and the power load centers in China have reverse distribution,and the load demand is constantly increasing.Energy transmission becomes a key problem related to national economy and people’s livelihood.Ultra-high-voltage(UHV)transmission is an effective solution to the problem of energy transmission in China,so the research of UHV halfwavelength alternating current transmission(HWACT)is of great significance.Traveling wave protection has its unique advantages for long-line and long-distance transmission.According to the up-wave propagation characteristics of half-wavelength lines,the traveling wave protection criterion suitable for half-wavelength lines is proposed.Aiming at the protection of the whole line of HWACT lines,and based on the theory of wavelet transform,the third-order B-spline function is chosen as the wavelet function in dyadic wavelet transform which is the main wavelet method for this protection,and the main body of the protection is constructed by using Mallat algorithm.The sample frequency,the wavelet transform scale and the target frequency band are determined based on the analysis of the frequency space characteristics of the half-wavelength circuit modulus and the amplitude frequency characteristics of the wavelet function coefficient sequence.Then a traveling wave pilot protection strategy suitable for the HWACT line is proposed,and the PSCAD/EMTDC and the MATLAB are used to conduct simulation and programming.The simulation results prove that the protection strategy can protect the full length of the HWACT line under various fault types as well as fault conditions and has a good ability to resist the transition resistance.