Bushing

with its‘plug-in’electrode structure

is different from general insulators in the electrode arrangement

and its electric field is very concentrated at the edge of bushing flange. In order to improve the external insulation strength of the bushing

according to the electric field distribution theory

gas discharge theory and surface discharge theory

in the existing structure of the HV bushing

namely

keeping electrode shape

electrode distance and dimension parameters of the insulator unchanged

and considering space charge factor

we placed the single or multiple accessories system mainly made of organic material on electrodes or insulator material

and converted the two-element structure（electrodes and insulator） of conventional insulator into a three-element structure. Namely

the insulator is made of three parts which are electrodes

insulator material

and organic material accessories system. Experimental results show that applied accessories system can raise the power frequency dry flashover voltage by 7.1% and raise pollution flashover voltage by 81.74% without changing the electrode shape

electrode distance and dimension parameters of the bushing. The findings have certain guiding significance as far as improving external insulation of HV wall bushing.