Composite insulators for transmission lines are one of the critical components in power systems

Brittle fracture of the core rod is one of the most severe defects in composite insulators during operation. A power frequency withstand voltage test was conducted on short samples of 1000kV composite insulators with brittle degradation

and the heating characteristics after core rod degradation were analyzed by observing infrared thermography. By analyzing the physical and chemical properties of the abnormally heated areas of the composite insulators and conducting finite element simulation calculations under different brittle conditions

the causes of abnormal heating in degraded composite insulators were identified. Test and simulation results indicate that severely degraded composite insulators exhibit significant abnormal heating phenomena

characterized by a wide heating range

high peak temperature rise

and heating not limited to the high-voltage end. The insulation resistance of the core rod significantly decreases after brittle fracture

and the dielectric loss angle significantly increases

leading to an increase in leakage current. Core rods with varying degrees of brittleness exhibit different levels of heating

as the conductivity and dielectric loss angle increase

the heating phenomenon intensifies.