General methods of detecting faulty insulators include the distribution voltage method

the corona pulse current method

the infrared thermal imaging temperature measurement method and the ultrasonic method

etc. They have

however

certain disadvantages. A brand-new ultra-violet (UV) pulse method proposed in this paper

through highly sensitive solar-blind UV detector

can continuously monitor the special wave band of UV pulses of discharge on the surface of insulators online. The UV pulse method to detect the faulty insulator is used because the faulty insulator will increase the number of the insulator string's discharge pulses. An on-line monitoring system adopting the UV pulse method doesn't need to have a touch with the insulator

and hence is very suitable for detecting faulty insulators online with the check distance beyond 4 m. The proposed method has been verified by experiments with a 110 kV line insulator.