Research Of Insulator Degradation Detecting Technology Based On Optical Electric Field Sensor

If there were insulating strength degradation in insulator strings oftransmission lines，it will be prone to flashover，which poses a serious threat togrid security. Composite insulators have been widely used in recent years becauseof their good performances in volume, weight, mechanical strength, vibration andpollution resistance, production cycle, and stability. However, there were nomethods or instruments that can detect degradation of composite insulators intransmission lines precisely and easily around the world.A method of measuring insulator degradation using optical electric fieldsensor was presented. Sensor and detecting system were designed on the basis oflightning effect principle, and the principles of selecting combination laser lightsource, optical crystal and photoelectric detector were proposed as well.Dual wavelength method was presented, and formula of calculating fieldintensity was derived to the question of measuring DC electric field with opticalsensors. Influencing factors of measuring accuracy, such as productive technologyof optical crystal, difference of sensor packaging materials, field intensity andmounting position were analyzed through experiments.Instrument for measuring field intensity in high voltage condition wasdesigned with optical electric field sensor being the essential component. Live linemeasurement approach for composite and other types of insulators was presented.FEM simulation model for field distribution of trailer composite insulator in220kv high-voltage test hall was set up. Theoretical field distribution of insulatorstrings was calculated, the correctness and effectiveness of which was verified bycomparing online experimental results.The paper introduced the experimental scheme of on-line monitoring ofinsulator strings.Results showed that the degradation of insulators withinhigh-voltage end, low-voltage end and middle sector could all be detected throughelectric filed measurement, which indicated that the method above could be aneffective approach for on-line detecting insulator degradation.