To clarify the effects of field strength components on the insulators flashover voltage

48 kinds of epoxy resin post insulators with different surface field strength distribution were cast as samples

and their flashover voltages under the standard lightning impulse were tested. According to the insulator surface electric field distribution results

which was calculated by finite element method

the relationships between maximum synthetic electric field(E

max

)

tangential electric field strength(E

tmax

) and normal electric field strength(E

nmax

) with flashover voltage U

f

were obtained. The results show that the correlat

ion coefficient between E

max

E

tmax

and E

nmax

and U

f

are-0.90

-0.84

and-0.73

respectively. According to the theoretical analysis of gas discharge

it is concluded that E

max

is the most important factor affecting the initiation of flashover discharge along the insulator surface and the transition of discharge mode

while E

tmax

is the secondary factor affecting the development of flashover along the insulator surface. According to the analysis of the connection condition of the electrostatic field at the gas-solid interface

it can be seen that reducing the E

nmax

by changing the shape of the insulator and the electrode structure can effectively reduce the E

max

along the surface

and can effectively restrain the accumulation of the surface charge of the insulator. Therefore

it is suggested that the synthetic electric field strength along the surface

its tangential and normal field strength should all be included in the design specification of the insulator electric field.