局部同塔双回直流线路故障行波传播特性及其对行波保护的影响研究

局部同塔双回直流线路分界点各侧的线路段具有不同的耦合特性,结合分界点各侧线路段的相模变换,得到了不同线路段入射分界点时各电压模量行波的交叉折射系数。在此基础上,对局部同塔双回线路不同线路区段发生单极接地故障时的故障行波传播特性及其行波保护动作量进行了定量分析,并比较了其与单回线路及完全同塔双回线路的差异。结果表明:同塔双回线路段的线模1分量与单回线路段的地模分量之间的交叉折射是造成局部同塔双回线路的故障行波传播特性与单回线路及完全同塔双回线路不同的主要原因;就基于模量的行波保护判据而言,局部同塔双回线路行波特性的影响主要体现在线模波变化率,其大小介于完全同塔双回线路和单回线路之间,且与单回线路段的总长度有关。

Propagation characteristics of fault travelling wave on double-circuit HVDC transmission lines partially on the same tower and its effect on travelling wave protection

Since there are different coupling characteristics of each side of the demarcation point for double-circuit HVDC transmission lines partially on the same tower, the approach to calculate the inter-refractive coefficient of every mode is obtained based on the phase-mode transformation in this paper. Then, propagation characteristics of fault travelling wave and criterion characteristics of travelling wave protection of single-pole-to-ground faults occurring in different line segments are investigated, and its differences from those on single-circuit HVDC lines and double-circuit HVDC lines are compared. It is shown that the travelling waves in the line-1 mode of double-circuit lines and earth mode of single-circuit lines can refract to passageways of each other, which is the important influencing factor for the propagation characteristics of double-circuit HVDC transmission lines partially on the same tower combining the extreme features of single-circuit HVDC lines and double-circuit HVDC lines. In terms of traveling wave protection based on modulus component, the influence of the traveling wave characteristics mainly embodies in the line-mode wave change rate. The size of line-mode wave change rate is between single-circuit HVDC lines and double-circuit HVDC lines and is related to the total length of single-circuit lines in double-circuit lines partially on the same tower. This work is supported by National Natural Science Foundation of China (No. 51577072).