Optimization of Potential and Electric Field Distribution for 750 kV Non-Gap Line Surge Arrester

The extra-high-voltage (UHV) non-gap line surge arrester (NGLA) is widely used in power system for lighting protections. Internal uneven potential distribution and electrical stress concentration may accelerate the aging of the metal-oxide resistor, shorten the service life of the arrester, posing great threat to the safe operation of the EHV system. This paper establishes a three-dimensional electric field simulation model of a canonical NGLA in 750 EHV system, studies its potential and electric field distribution, and analyzes the influence of arrester structure on its performance. It is found that due to the large stray capacitance of the high-voltage arrester to the ground, it is difficult for the grading ring to compensate the stray capacitance under the initial structure, resulting in the maximum voltage nonuniformity coefficient of the fourth resistor of the arrester reaching 1.41 and the maximum electric field strength reaching 2.19 kV/mm, which has a significant risk of aging and failure. On this basis, a variety of grading ring configuration schemes are designed to optimize the structure of the arrester. Compared with the initial structure, the non-uniform coefficient of potential distribution and local field strength are effectively reduced.