Affected by extreme freezing rain

snow and other severe weather

an ice-covered broken line accident occurred in the optical cable of a ± 800 kV UHV overhead transmission line. In this paper

the causes of wire breakage are analyzed from the perspectives of design verification

field investigation

metallographic and microscopic examination. It is concluded that the accident is mainly due to the lightning strike of the optical cable

the failure of the single wire ablation damage to eliminate the defect in time

and the superposition of freezing rain and icing

resulting in the super yield strength fracture of the mechanical properties of the optical cable. According to the reasons for the disconnection

it is proposed that the design stage should increase the identification of micro-topography and micrometeorology

and the differentiated design should enhance intrinsic safety. The operation and maintenance unit should increase the line conductor and ground wire inspections according to the lightning strike near the line.