The heat source for the abnormal heating of composite insulators is generally located at the mandrel-sheath interface or on the sheath surface. Fiber Bragg gratings are used to measure the transient temperature rise on the mandrel-sheath interface and the sheath surface of the composite insulator under interface and surface heat source. The measurements are performed on a 10 kV composite insulator. The experimental results show that the time constants of interface temperature rise and surface temperature rise under the interface heat source are about 40 s and 115 s, respectively. In comparison, they are 100 s and 7 s respectively under the surface heat source. When the heat source is applied to the mandrel-sheath interface, it takes 15-50 min and 15-35 min respectively, for the interface temperature and surface temperature to stabilize; while it takes 9-18 min and 8-16 min respectively for the interface temperature and the surface temperature to reach stability under surface heating. The rise amplitude of the interface temperature and the surface temperature both show a linear relationship with the applied heat. The difference between the interface and surface temperature increases with increasing applied heat.

composite insulator,,abnormal heating,,transient temperature rise