强风区750kV复合绝缘子抗风性能研究

Study on Wind Resistance Performance of 750 kV Composite Insulators Utilized in Storm-wind Region

在我国西北部的特高压输电线路中,复合绝缘子被广泛应用,但途经＂三十里风区＂的750 kV输电线路,在运行不到一年时间内,就出现大量绝缘子伞裙根部断裂故障。强风条件下伞裙发生持续稳定的强烈摆动,最终导致硅橡胶材料疲劳断裂。该文首先利用有限元软件分析流体中复合绝缘子的受力情况,研究绝缘子各部位的风压分布和伞裙附近的流场特点;其次提出一套复合绝缘子风洞实验方法,研究两支典型750 kV复合绝缘子在25～60 m/s风速范围内的伞裙动态过程。风洞实验研究发现,在V型串的悬挂方式下,背风侧绝缘子串伞裙相对迎风侧绝缘子更易起振,且芯棒与来流夹角的变化对其起振风速影响显著,最不利来流迎风角在50°;绝缘子的停振风速相对于起振风速降低最高可达17.6%;通过不同风速下伞裙摆动频率和幅度研究,发现随风速的升高,摆动频率较稳定,但摆动幅度会明显提高,伞裙摆动幅度最大可达伞间距的79%。

Composite insulators are extensively applied on extra high voltage（EHV） transmission lines in northwestern China whereas large amount of them have shed fracture failure after only one year＇s operation on the 750 k V transmission lines across the ‘thirty miles storm-wind district＇. The sheds have the oscillation phenomenon under strong wind which at last leads to the fatigue failure of silicone rubber. This paper first utilized finite element software to simulate the fluid and mechanics problem of insulator. The streamlines of fluid and the wind stress distribution around insulator structure were analyzed. A set of wind tunnel test method was proposed to research the dynamic process of sheds under the wind velocity from 25 m/s to 60 m/s. The test results show that： Compared with left side of V string that towards incoming wind, the right side is more vulnerable to be vibrated. With the suspension type V string, various inclination angles were tested and the critical angle that leads to lowest inception wind velocity is 50°; The extinction wind velocity is normally lower than inception wind velocity and the gap can reach 17.6%. This paper also studied the frequency and extent of shed oscillation under different wind speeds, it＇s found that the frequency is relatively steady but the extent of oscillation increases significantly with the rise of applied wind velocity, the oscillation extent can reach 79% of the spacing of sheds.