高海拔地区500kV变电站设备相间操作冲击放电特性

Phase-to-phase Switching Impulse Discharge Characteristics of 500 kV Substation Equipment in High-altitude Area

相间操作冲击放电特性是决定变电站设计尺寸的一个重要方面。为获得我国高海拔地区500kV变电站的设计依据,结合云南电网公司500kV建塘输变电工程,分别在3个不同海拔高度地区武汉(23m)、西宁(2 254m)、大武(3 742m),开展了模拟真型500kV变电站典型电极—软母线和均压环的相间操作冲击试验研究。利用升降法获得5～8m间隙距离内的相间操作冲击放电特性曲线,分析电压分配系数对相间间隙空气绝缘的影响,并按不同的海拔校正方法对试验结果进行校正分析和比较。试验表明:受海拔高度的影响,高海拔变电站设备相间操作冲击平均击穿场强较低海拔有明显的下降,相间操作冲击放电电压U50随着电压分配系数增大而增大。通过对比国内外不同海拔校正方法,建议高海拔地区500kV变电站均压环相间操作冲击海拔校正采用IEC 60071-2—1996标准的方法进行海拔校正;软母线相间操作冲击海拔校正采用带m因子的修正方法进行海拔校正。

Phase-to-phase switching impulse discharge characteristics play an important role in the design of substation equipment. In order to get the design foundation of 500 kV substations at high altitudes in China, taking into account of 500 kV Jiantang transmission project in Yunnan Province, we practically simulated and tested phase- to-phase switching impulse discharges between flexible buses or grading rings and a typical electrode pair in 500 kV substations. The experiments were performed in 3 areas at different aItitude： Wuhan 23 m, Xining 2 254 m and Dawu 3 742 m, in which phase-to-phase switching impulse discharge curves for gaps of 3-8 m were obtained using the up-and-down method. The influences of voltage distribution coefficients on the gas insulation of phase-to phase gaps were analyzed, and the experimental results were corrected for the altitudes and then comparatively analyzed. It is concluded that the discharge voltage of air gap decreases sharply with increasing altitude, meanwhile, U50 the 50% switching impulse discharge voltage of phase-to-phase insulation, increases with the voltage distribution coefficient. According to a comparison among several altitude-correction methods, the method in IEC 60071-2-1996 and the m-factor involved altitude correction method are suggested for phase-to-phase switching impulse＇s altitude corrections of grading rings and flexible buses in 500 kV substations at high altitudes, respectively.