计及波速变化的反行波直流输电线路故障测距方法

行波法、故障分析法、固有频率法是高压直流输电故障测距中常用的3种方法。行波法因其波头识别问题导致可靠性不高，波速的选择也影响了测距精度的大小；故障分析法受模型精度的影响测距精度不高；固有频率法在线路终点发生故障时存在死区。直流线路故障时第一个反行波一般不受反射系数频变的影响，基于反行波波头容易识别的特性，采用反行波进行故障测距，波头的识别采用奇异性检测效果优异的à trous算法，针对直流线路采用不同型号导线导致波速不一致的情况，对不同型号线路段采用不同的波速进行计算，进一步提高测距精度。相较于现有的故障测距算法，本算法波头识别的可靠性得到提高，且由于计及了波速的变化，在直流线路采用不同型号导线时测距精度进一步提高。

Fault Location of DC Transmission Lines Based on Backward Waves Considering Wave Speed Changes

The fault location methods of UHVDC transmission lines can be divided into traveling-wave-based algorithm, fault-analysis-based algorithm and natural-frequency-based algorithm according to the principle. The traveling-wave-based algorithm is not reliable due to its wave head identification problem, and the choice of wave speed also affects the accuracy of fault location; The fault location accuracy of the fault-analysis-based algorithm is not high because of model accuracy; The natural-frequency-based algorithm has dead zone when the fault occurs at the end of the line. This paper presents a novel fault location algorithm, when the DC line fault occurs, the first backward-wave has not been reflected, and it is not affected by the frequency variation of the reflection coefficient, the backward-wave head is easy to identify, so the backward-wave is used for fault location in this paper. The identification of wave head uses the à trous algorithm with excellent singularity detection capability. In the case of inconsistent wave speeds caused by the use of different types of conductors on the DC line, the calculation is performed with different wave speeds to improve the range accuracy further. Compared with the existing fault location algorithm, the reliability of the wave head identification of this algorithm is improved, and since the variation of the wave speed is taken into consideration, the ranging accuracy is improved further when different types of wires are used in the DC line.