IEEE ICHVE 2022 / 1-PAGE ABSTRACT
Compatibility Study of Silicone Rubber with Capacitor Impregnation Fluid
Yujia Ban, Ruan Li, Xiangyang Li, Jiakai Zeng, Lu Cheng, Wenfeng Liu*
State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University
banbanlearning@163.com, 2194214320@stu.xjtu.edu.cn, lxy2013zlywai@qq.com,  1195780248@qq.com, chenglu@xjtu.edu.cn, liuwenfeng@xjtu.edu.cn*

Purpose
Oil leakage of capacitor is one of the main reasons for the failure of oil-immersed power capacitor, and the deterioration of the sealing performance of capacitor bushing is the main cause of oil leakage. On the one hand, the performance of the sealing ring is aging with the extension of operating time; on the other hand, there may be a compatibility risk between the rubber material used for the sealing ring and the capacitor impregnation fluid, which means that serious physical or chemical changes may occur between the rubber and the capacitor impregnation fluid in the actual use process, resulting in the rapid deterioration of the capacitor sealing performance.
For more than half a century since the appearance of oil-immersed power capacitors, there is little research on the compatibility of oil-immersed capacitors, and there is no general standard for testing the compatibility of capacitor impregnation fluid and sealing materials. The existing research mainly focused on the interaction between biaxially oriented polypropylene (BOPP) and capacitor impregnation fluid in the process of replacing capacitor paper in the last century. The only compatibility research was mainly related to transformers. In addition, at present, the testing method of compatibility was relatively single, and the theoretical basis research was weak. Therefore, it is of great significance for practical production guidance and theoretical research to study the compatibility test method of oil-immersed capacitor sealing material and impregnant.
Experimental methods
In this paper, silicone rubber, which is commonly used in capacitor bushing sealing ring, was selected as the test object to study its compatibility with capacitor impregnation fluid, Jarylec C101. Under the condition of constant temperature of 105℃, the performance of rubber and capacitor insulating liquid was studied after the silicone rubber was placed in the capacitor insulating liquid Jarylec C101 at the ratio of 65cm2 to 800ml for 168 hours, 336 hours, 504 hours and 672 hours. The volume, mass and hardness of silicone rubber were analyzed, and its tensile strength and compression set were tested. The moisture content, dielectric loss, breakdown voltage and acid value of capacitor insulating liquid were tested.
Results
Through the analysis of experimental results, it was found that the mass and volume of silicone rubber increased compared with that in the dry state, and the mass increased continuously with time, while the volume hardly changed with time.  The hardness decreased significantly during 0-168h, and then rose to a stable level. The tensile strength and elongation at break of silicone rubber decreased continuously from 0 to 336 h, while the compression set increased continuously during the whole compatibility test. The dielectric spectrum and breakdown test results of the capacitor impregnation fluid showed that its insulation performance has declined.
Conclusions
Compared with the previous industry-related test methods, the test method of compatibility between impregnant and rubber seal of oil-immersed power capacitor studied in this paper prolonged the interaction time between insulating liquid and rubber, increased the test items of rubber seal, and obtained a comprehensive and scientific test standard of compatibility between impregnant and rubber seal of capacitor. Combining the compatibility evaluation test with the mechanism research experiment, the interaction mechanism between capacitor impregnation fluid and rubber sealing material was revealed, and the standard of capacitor compatibility test was improved from the mechanism point of view. It can provide experimental and theoretical basis for establishing international general test standards, and guarantee the safe and stable operation of oil-immersed power capacitors and the whole power system.

 

compatibility,capacitor,gasket,insulating liquid