Bird damage has become one of the most important factors endangering the safe operation of transmission lines

which degree of harm is second only to lighting and external forces

while streamer flashover is the most typical type

ranking the first of all bird damage. The paper presents a preventive measure against streamer flashover by wrapping insulation sheath to wire. Tests results show that the potential of equalizing ring decreases after wrapping insulation sheath

which effectively avoid the occurrence of discharge between streamer channel and equalizing ring

as a result

scope of risk area decreases. Besides

the paper also establishes threedimensional simulation model

calculating the effect of insulation sheath on composite insulator under different value of dielectric constant

thickness of insulation sheath and length of fittings. Results show that wrapping insulation sheath decreases the potential of equalizing ring and decrease the possibility of streamer flashover

besides

the electric field distribution along the surface of the composite insulator is improved

enabling its safe operation.