±1100 kV特高压直流杆塔间隙放电特性

Discharge Characteristics of ±1100 kV UHV DC Tower Air Gaps

±1100 kV直流是一个新的电压等级,杆塔间隙距离的选择是保证工程可靠和经济的关键技术之一,我国正在建设的±1100 kV输电线路超过3000 km,并且途经高海拔地区,为解决杆塔间隙放电电压的海拔校正问题,在国内两个不同海拔的试验基地,采用±1100 kV真型尺寸模拟杆塔,进行了空气间隙冲击放电试验,获得了相应的操作冲击、雷电冲击放电电压,并分析了不同海拔下操作冲击和雷电冲击放电电压的分散性;其次,利用典型的棒板间隙操作冲击放电公式,分析了间隙距离6~11 m范围的间隙系数;然后,结合IEC 60071-2规定的海拔校正方法,分析了±1100 kV杆塔操作冲击和雷电冲击的海拔校正系数,并计算得到了操作冲击的电压修正因数m。最后结合昌吉—古泉±1100 kV工程的过电压计算结果,推荐了海拔3000 m及以下地区±1100 kV输电线路直流电压和操作冲击电压所需的最小间隙距离。结果表明：未发现海拔的变化对间隙放电电压的相对标准偏差有明显影响,在1.57 pu操作过电压下,海拔1000 m时,±1100 kV输电线路杆塔操作冲击所需的最小间隙距离为8.9 m,海拔为3000 m时,最小间隙距离为9.8 m。直流电压要求的间隙距离较小,海拔3000 m时为4.2 m。

±1100 kV DC transmission line is of a new higher voltage level. In order to guarantee design reliability and rationality, air clearance choice is very important and need to be researched. The same configuration and real size simulation tower of ±1100 kV DC line was used to carry out impulse voltage test at SGCC UHVDC test base in Beijing and Tibet high altitude test base located at 4300 m above sea level. Test curves of flashover characteristics of switching impulse and lightning impulse were acquired, and dispersion of switching impulse and lightning impulse discharge voltage at different altitudes was analyzed. Gap factors in range of 6 m^11 m were analyzed using switching impulse of typical rod-plane gap. Then, according to altitude correction method stipulated in IEC60071-2, voltage correction factors of ± 1100 kV tower switching impulse and lightning impulse were analyzed, and voltage correction factor m of switching impulse was calculated. Finally, combined with the results of overvoltage calculation of a real ± 1100 kV transmission line project, minimum gap distance of switching impulse voltage and DC voltage for ± 1100 kV transmission line at altitude 3000 m and below was recommended. Results show that altitude has no obvious effect on dispersion of impulse discharge voltage. For switching overvoltage 1.57 pu, the minimum gap air distance on ±1100 kV DC transmission line tower is 8.3 meters at altitude 1000 m, the minimum air gap distance is 9.8 m at altitude 3000 m. DC voltage requires smaller gap distance, 4.2 m at altitude 3000 m.