改性聚酰亚胺沿面放电特性研究

Study on Surface Discharge Characteristics of Modified Polyimides

聚酰亚胺材料以其优越的介电性能广泛应用于电力系统的绝缘中,其表面发生沿面放电是影响其绝缘性能的关键因素之一。利用自行搭建的试验系统,以纯聚酰亚胺、玻璃纤维和钛酸钾改性的聚酰亚胺为研究对象,借助扫描电子显微镜,分析其表面碳化情况,并测量其在标准大气压、低气压和高真空三种状态下的电气强度。结果表明:含有钛酸钾的聚酰亚胺材料和直角倒角的纯聚酰亚胺材料碳化现象不太明显。扫描电镜显示,低气压下绝缘材料表面比标准大气压下的平滑,含有玻璃纤维和钛酸钾的聚酰亚胺材料表面均出现孔洞。标准大气压下,含有钛酸钾的聚酰亚胺材料电气强度最低,含有玻璃纤维的聚酰亚胺电气强度最高;低气压下,含有玻璃纤维的聚酰亚胺材料电气强度最低,厚度较小时,含有钛酸钾的聚酰亚胺材料电气强度略低于纯聚酰亚胺;高真空下,纯聚酰亚胺的绝缘性能最好。

Polyimide is widely used in power system as insulation because of its excellent dielectric property, but its insulating properties would be affected by surface discharge, which is one of the key infulence factors. Using pure polyimide, glass fiber and potassium titanate modified polyimide as research objects, we analyzed their surface carbonization condition, which tested on the self-built test system, by scanning electron microscopy （SEM）, and measured their electric strength under atmospheric pressure, low pressure, and high vacuum. The results show that the carbonization phenomena of the potassium titanate modified polyimide and pure polyimide with rectangle chamfer is not obvious. SEM results show that the surface of insulating materials is smoother under low pressure than normal atmospheric pressure, and the glass fiber and potassium titanate modified polyimides appear holes on their surface. Under normal atmospheric pressure, the potassium titanate modified polyimide has the lowest electric strength, while the fiber glass modified polyimide has the highest electric strength. Under low pressure, the fiber glass modi- fied polyimide has the lowest electric strength, and the electric strength of titanate modified polyimide is slightly lower than that of the pure polyimide when the thickness is small. Under high vacuum, the pure polyimide has the best insulating properties.