基于Hilbert能量幅值信息和波形信息的特高压直流输电线路单端保护方法

Single-Ended Protection Method for UHVDC Transmission Line Based on Hilbert Energy Amplitude Information and Waveform Information

直流输电系统具有强非线性,采用叠加原理和小波变换算法的直流输电线路行波保护存在适应性问题;仅利用行波暂态量幅值信息的直流输电线路行波保护在线路末端故障时存在保护拒动的问题。针对此问题,提出一种特高压直流输电线路单端保护方法。通过研究特高压直流输电线路两端物理边界特性,推导出Hilbert能量波形信息与电压行波的关系式,得出物理边界对Hilbert能量波形具有平滑作用。分析物理边界元件和直流输电线路频率特性,发现物理边界元件和直流输电线路对暂态高频分量具有衰减作用,据此利用Hilbert能量表征高频分量衰减情况。直流输电线路区内、外故障时,暂态电压5~7kHz高频带Hilbert瞬时能量幅值和波形形状差异明显,利用标准差综合描述高频带Hilbert能量幅值信息和波形信息,构造直流输电线路故障识别判据。利用正、负极标准差之比构造故障选极判据,实现故障极全线速动保护。仿真结果表明,该保护方法能可靠区分直流线路区内、外故障,实现故障选极,保护特高压直流线路全长。

The DC transmission system has strong nonlinearity.The traveling wave protection of DC transmission line using the superposition principle and wavelet transform algorithm has the adaptability problems.The traveling wave protection of DC transmission lines only uses the amplitude information of traveling wave transient.There is a problem with protection refusal at the end of the fault.Aiming at this problem,a single-ended protection method for UHVDC transmission line is proposed.By studying the physical boundary characteristics at both ends of the UHVDC transmission line,the relationship between the Hilbert energy waveform information and the voltage traveling wave is derived,and the physical boundary is smoothed to the Hilbert energy waveform.The physical boundary element and the frequency characteristics of the DC transmission line are analyzed.It is found that the physical boundary element and the DC transmission line have attenuating the transient high-frequency component,and the Hilbert energy is used to characterize the attenuation of the high-frequency component.In the case of faults in the DC transmission line,the transient energy amplitude and waveform shape of the high-frequency transient band 5~7kHz are obviously different.The standard deviation is used to describe the high-band Hilbert instantaneous energy amplitude information and waveform information to construct DC.Transmission line fault identification criteria.The fault selection criterion is constructed by using the ratio of the standard deviation of the positive and negative poles to realize the full-line quick-action protection of the fault pole.The simulation results show that the protection method can reliably distinguish faults in the DC line and outside,realize fault selection,and protect the full length of UHVDC lines.