KANG Meicun， CHEN Qijie， RONG Zhi， ZONG Zhangyang， GAO Xin(School of Chemistry and Food Engineering，ChangshaUniversityofScienceandTechnology，Changsha410114，China)Corresponding E-mail： chenqijie@csust．edu．cn

Key words: transformer insulating paper; celluose nanocrystals; breakdown strength; tensile strength

Transformer is one of the most important electrical equipment in power system and its performance directly affects the safe operation of power systems． Currently， most transformers are oil-immersed transformers， and the insulation system consists of insulating oil and insulating paper． The quality of insulating paper mainly includes the electrical and mechanical properties and the main purpose of insulating paper impregnated with insulating oil is to resist the flow of electric current between conductors． The main reason for the failure of power equipment is the deterioration of its insulation performance， of which the aging process of insulating paper is irreversible，which is the main reason for the failure of power transformer． Thus the quality of insulating paper is very important， which determines the service life of the transformer．

In this study， celluose nanocrystals (CNC) including T-CNC prepared by TEMPO-Oxidized method with dissolved pulp and S-CNC prepared by sulfuric acid hydrolysis method with bleached kraft softwood pulp were used to improve the mechanical and electrical properties of the transformer insulating paper． The insulating paper containing T-CNC and S-CNC were characterized by Fourier transform infrared spectroscopy(FTIR) and Xray diffraction(XRD)． The effects of different amounts of CNC on tensile strength， AC breakdown strength， oil absorption rate and conductivity of insulating paper were studied． The results showed that CNC can effectively improve the mechanical and electrical performances of insulating paper， and the effect of T-CNC is better than that of S-CNC．When the T-CNC dosage was 0．9%， the tensile strength， AC breakdown strength in oil， oil absorption rate of the insulating paper were 70．22 N·m/g， 59．78 kV/mm， 53．08% respectively， which was improved by 21．7%， 24．57%and 39．4% respectively than that of the reference insulating paper． Also the beating degree of pulp affect the mechanical and electrical properties of insulating paper containing CNC．