热压温度对绝缘纸性能的影响

Effect of Hot-pressing Temperature on Insulation Performance of Insulation Presspaper

随着特高压输电工程的建设,换流变压器绝缘故障频发。高性能绝缘纸的匮乏已在一定程度上影响到设备安全和系统稳定。热压作为绝缘纸生产制备的关键环节,优化热压参数有助于提升绝缘纸的机械、电气性能。为此,选取热压温度为105、115、125、135℃制备绝缘纸试样。对所得试样,利用傅里叶红外光谱（FTIR）和X–射线衍射（XRD）分析了化学官能团和结晶度变化变化,并测试了抗张强度、体积电阻率和击穿特性。结果表明,热压温度为105℃时,纤维之间的结合强度相对较低。随着热压温度的上升,绝缘纸的结晶度先增加、后略微降低。热压温度对抗张强度和直流击穿场强有显著影响,对体积电阻率和交流击穿场强影响不大。125℃下绝缘纸可获得最高的抗张强度,为121.8 MPa,比105℃下的最低值高出25%。105℃下绝缘纸的直流击穿场强最高,为23.1 k V/mm,比最低值高出15%。考虑到将热压温度从125℃增加到135℃并不能显著提高绝缘纸的性能,对该研究所涉及的400μm厚绝缘纸,建议热压温度保持在125℃以下。

With the development of UHVDC power transmission, insulation failures in ultra-high voltage convert transformers become a severe problem. The lack of high-quality insulation presspaper has already affected the safety of power equipment and reliability of the power system. Since hot-pressing is a key process in the manufacture of the presspaper, optimizing hot-pressing parameters probably contributes to the improvements of mechanical and electrical properties. Thus, four different hot-pressing temperatures, namely 105, 115, 125, and 135 ℃, were used to prepare presspaper samples. Obtained samples were characterized by Fourier transform infrared spectroscopy（FTIR） and X-ray diffraction（XRD）. Mechanical properties, volume resistivity, and breakdown behaviors were also measured and analyzed. Results show that presspaper made at 105 ℃ has a lower inter fiber bond strength. Crystallinity index of presspaper first increases, and then deceases with the increasing of hot-pressing temperature. The effect of hot-pressing temperature on tensile strength and DC breakdown field is obvious, whereas hot-pressing temperature has a small influence on volume resistivity and AC breakdown strength. Presspaper prepared at 125 ℃ can get the highest tensile strength of 121.8 MPa, which is 25% higher than the specimen made at 105 ℃. Samples prepared at 105 ℃ can achieve the maximum DC breakdown strength of 21.1 kV/mm, which is 15% higher than the lowest one. Considering that no improved performances of presspaper are observed when increasing hot-press temperature from 125 ℃ to 135 ℃, we suggest that hot-press temperature should be lower than 125 ℃ for presspaper with a thickness of about 400 μm.