Study on improving the operation performance of composite insulator by interpolation electrode structure

In power grid, higher is the voltage level, longer is the composite insulator string, uneven is the potential distribution, especially the sheds near the conductor, its withstand voltage is several times higher than other sheds. For the electric field strength of composite insulator at high end is high, it is easy to produce corona which resulted in insulator degradation, life shortening and acid corrosion intensified by electric corrosion. A new interpolation electrode structure equipped with optimized grading ring is designed and developed to effectively improve potential distribution of composite insulator. Based on fuzzy clustering analysis method, the test data of 330kV composite insulator with different structures is analyzed and modeled. Field strength distribution function of composite insulator with different structure has obtained. Through field strength analysis, it is proposed to introduce the potential into 1~2 sheds of composite insulator core rod for reducing field strength at high end. Based on above method, a new interpolation electrode structure is designed; optimal design is conducted to grading ring of interpolation electrode structure through finite element algorithm simulation. The product has passed all type tests. Field strength and potential distribution of insulator shed are measured by fiber optic field strength measuring instrument. It is shown that the potential distribution of composite insulator has been improved greatly. The product has been applied and operated on a 330kV transmission line in Shaanxi Province for 3 years, and is under good operation condition.