71 / 2018-08-23 10:39:32

Simulation on Electrical Field Distribution of Polluted HVDC Wall Bushing

Finite Element Method (FEM),BUSHING,Pollution,electrical field distribution

Recent years have witnessed the booming period of Ultra High Voltage Direct Current（UHVDC）because of its advantages in huge transmission capacities, far transmission distance and high voltage level. Hence significance of the security of the devices and equipment in UHVDC transmission, including HVDC wall bushing and other devices is more emphasized. These apparatus are pivotal components in the substation, which act as a role of supporting conductor and electrical insulation.
Valve hall is a vital part in UHVDC transmission and undertakes the task of commutation. Varieties of devices and instruments are placed in the valve hall in complex spatial location, making electric field distortion more serious, especially on the ends of wall bushing. Moreover, the complex electromagnetic environment and superimposed AC/DC voltage in the valve hall will worsen the circumstance. While undertaking the task of electrical insulation and mechanical support for other equipment, HVDC wall bushing is quite possible to be fouled when exposed to external environment which may worsen the performance of the HVDC wall bushing. Raindrop, dust and dirt on the surface of the bushing, especially their mixture may influence the electrical distribution, eventually leading to surface discharge and flashover as well as the deterioration of internal properties. Thus it is essential to conduct research on electrical field distribution of HVDC wall bushing and to obtain its characteristic.
In this paper, the calculation model of ±400kV wall bushing was established using the FEM (finite element method) software COMSOL. Effects of several different types of fifth which located on the surface of the wall bushing was separately studied to get the feature of diverse kinds, including that contamination was uniformly distributed on the surface of the wall bushing as well as it was only at the root of the bushing shed. Also, the non-uniformly distributed wetting condition was taken into account. The electrical field was obtained in all circumstances above and the distribution feature was concluded. In addition, the inner shielding structure was optimized to enhance the e-field distribution. In that case, the influence of different types of pollution on the surfaces of the HVDC wall bushings was obtained, with the structure of the HVDC wall bushing optimized.
This result based on numerical calculation could provide theoretical basis for effect of different types of contamination on the surface of HVDC wall bushing. The optimization for the inner shielding structure could help improve the design of HVDC wall bushings in the valve hall and reduce the probability of fault like flashover and surface discharge, further to improve the operational security level of the whole substation.