【作者】 刘江；

【导师】 冉慧娟； 王彦朋；

【作者基本信息】 华北电力大学 ， 能源动力硕士（专业学位）， 2024， 硕士

【摘要】 冬季输电线路覆冰荷载会影响输电线路的机械性能及绝缘性能,进而影响电网的稳定运行,对覆冰线路开展融冰是电力系统每年冬季的重点工作。在现有的线路融冰方法中,直流融冰具有更大的优势。为了提高融冰效率,通常需要一个融冰装置串接多条线路同时开展融冰工作,对于变电站来说,只能借助母线来实现线路的串接。然而,气体绝缘变电站内部的盆式绝缘子会在直流电压作用下发生表面电荷积聚,造成局部电场畸变,诱发沿面闪络,难以保证切换交流电压后的安全稳定运行。因此,本文通过实验探究环氧树脂复合材料在交直流电压下表面电荷积聚特性及电荷积聚对材料沿面闪络的影响,研究结果可为气体绝缘开关设备优化设计提供参考数据。首先,搭建环氧树脂复合材料样片制备平台,制备实验测试所需的环氧树脂复合样片;搭建材料电晕充电及截断相位记录平台、试样表面电荷性能测试平台和试样交直流闪络特性测试平台,对试样进行表面充电时记录交流切断瞬间的截断相位,为后续进行表面电荷测试及闪络测试提供不同的初始实验条件。然后,将充电后的试样置于试样表面电荷性能测试平台,在直流电压、交流电压、交直流切换电压下对环氧树脂复合材料的表面电荷分布进行测试及分析。在直流电压下,试样表面电荷积聚情况随施加电压幅值和作用时间的增加而增加,施加电压正负极性仅影响积聚在试样表面的电荷极性,而对试样表面电荷分布情况影响不大;在交流电压下,电荷积聚分布随截断相位发生周期性变化,而电压作用时间会导致试样表面的电荷积聚加深;在交流切直流电压下,试样表面电荷积聚情况与仅施加直流下的电荷积聚情况相似;在直流切交流电压下,试样表面电荷极性与直流电源极性保持一致,而电荷积聚分布变化情况与施加交流电压的影响因素有关。最后,将试样置于环氧树脂复合材料交直流闪络特性测试平台,通过在试样表面预置电荷的方式,对比未预置电荷和预置电荷后不同消散时长的材料沿面闪络电压数据,研究试样表面电荷积聚对沿面闪络的影响机制。发现电荷消散初期试样的沿面闪络电压会降低,消散一段时间后,试样的沿面闪络电压又有所回升且与未预置电荷时试样的沿面闪络电压相近,推断出试样表面浅陷阱脱陷的电荷为试样发生沿面闪络提供了种子电荷。更多还原

【Abstract】 The ice load of transmission lines in winter will affect the mechanical properties and insulation properties of transmission lines,and then affect the stable operation of the power grid.The ice melting of ice-covered lines is the key work of the power system every winter.Among the existing methods of line ice melting,DC ice melting has more advantages.In order to improve the efficiency of ice melting,it is usually necessary for an ice melting device to connect multiple lines at the same time to carry out ice melting work.For substations,the line can only be connected by bus.However,the basin insulator inside the gas-insulated substation will accumulate surface charge under the action of DC voltage,causing local electric field distortion and inducing flashover along the surface,which is difficult to ensure the safe and stable operation after switching AC voltage.Therefore,this paper explores the surface charge accumulation characteristics of epoxy resin composites under AC and DC voltage and the influence of charge accumulation on the material’s flashover along the surface through experiments,and the research results can provide reference data for the optimal design of gas-insulated switchgear.Firstly,the preparation platform of epoxy resin composite material sample was built to prepare epoxy resin composite sample required for experimental test.A recording platform for corona charging and truncation phase of materials,a testing platform for surface charge performance of samples and a testing platform for AC-DC flashover characteristics of samples were built to record the truncation phase at the moment of AC cut-off during surface charging of samples,providing different initial experimental conditions for subsequent surface charge testing and flashover testing.Then,the charged sample was placed on the surface charge performance test platform,and the surface charge distribution of the epoxy resin composite was tested and analyzed under DC voltage,AC voltage and AC/DC switching voltage.Under DC voltage,the charge accumulation on the surface of the sample increases with the increase of the applied voltage amplitude and time.The polarity of the applied voltage only affects the charge polarity on the surface of the sample,but has little effect on the charge distribution on the surface of the sample.Under AC voltage,the charge accumulation distribution changes periodically with the truncation phase,and the voltage action time will cause the charge accumulation on the sample surface to deepen.The charge accumulation on the surface of the sample is similar to that of DC only under AC cut DC voltage.The polarity of the surface charge of the sample is consistent with the polarity of the DC power supply,and the variation of the charge accumulation distribution is related to the influence factors of the applied AC voltage.Finally,the sample was placed on the test platform for the AC-DC flashover characteristics of epoxy resin composites.By presetting charge on the surface of the sample,the flashover voltage data of materials with different dissipation times after presetting charge and without presetting charge were compared to study the influence mechanism of sample surface charge accumulation on the flashover along the surface.It is found that the surface flashover voltage of the sample will decrease in the initial stage of charge dissipation,and after dissipating for a period of time,the surface flashover voltage of the sample will rise and be similar to that of the sample without preset charge.It is inferred that the charge of the shallow trap on the surface of the sample provides the seed charge for the sample’s surface flashover.更多还原