特高压直流接地极线路招弧角绝缘配合试验研究

Experimental Research on Insulation Coordination of Arcing Horns on UHVDC Earthing Lines

为了研究招弧角在电压等级为±800 kV、输送功率为5 000 MW的某特高压直流输电系统接地极线路上的绝缘配合情况,开展了燃弧试验,并采用U-I特性配合法进行了绝缘配合分析,研究了接地极线路参数和电弧拉伸效应对招弧角保护性能的影响。试验中,招弧角间隙距离为400 mm至1 500 mm,采用最大脉冲宽度为70 ms、最大电流幅值为2 500 A的脉冲电流源作为输出电源。研究结果表明:招弧角对长距离、大容量接地极线路的保护效果有限,间隙距离为1 500 mm的招弧角仅能保护31%长度的接地极线路;招弧角保护范围随着线路电阻的降低和杆塔接地电阻的增大而增加,但在线路电阻较大时,随杆塔接地电阻的变化趋势不明显,例如杆塔接地电阻由5?提高到15?,保护范围仅增加线路全长的9%;在电磁力和热浮力的作用下,电弧长度会大于间隙距离,应考虑电弧拉伸效应采用拉伸后的电弧长度作为等效间隙距离,如间隙距离为1 000 mm时最大电弧长度超过1 600 mm,若按拉伸后的电弧长度考虑,则其保护范围将由12%提高为33%。在实际情况中,因电源供能充足,电弧将会持续燃烧,拉伸更为充分,故招弧角的保护效果更为乐观。

We analyze the insulation coordination of arcing horns on the earthing lines of a ±800 kV, 5 000 MW UHVDC system. Moreover, we experimentally study the arc extinction characteristic of arcing horns, and introduce U-1 characteristic method to investigate the protection region of the arcing horns. The influences of line parameters and arc elongation are analyzed in detail as well. The discharge gap distance of the arcing horns is from 400 mm to 1 500 mm. A pulse-wave generator is chosen as the power supply. The maximum output pulse width is 70 ms, and the peak current is 2 500 A. The results indicate that the arcing horns have limited fault clearing efficiency, especially on long distance and high capacity UHVDC earthing lines. For example, the arcing horns of I 500 mm discharge gap distance can only protect 31% of the UHVDC earthing line. The fault cleating efficiency is significantly improved with the decrease of the line resistance, but slightly improved with the increase of the tower footing resistance especially at a higher line resistance. The protection region of the UHVDC earthing line increases by 9% even if the tower footing resistance rises from 5Ω to 15Ω On the other hand, due to the effect of magnetic and thermal buoyancy forces, the actual length of the arc is much longer than the discharge gap length （e.g. the maximum length of the arc for 1 000 rnm discharge gap distance is 1 600 mm）. Hence, the effect of arc elongation should be taken into consideration. Since the UHVDC earthing line will provide more power than experimental circuit, the arc will keep burning and elongating. That means the practical performance of the arcing horns is more optimistic.