Whats composite insulators detection technology?

    Because of its light weight composite insulators, high strength, high tolerance flash performance, easy maintenance and many other advantages of manufacturing and widely applied in the power system, breaking the long-term dominance of porcelain and glass insulators. According to incomplete statistics, in 2001, the total number of grid operation has reached 1.6 million, about 2.9 million years, on the use of quantitative terms, China has become second only to the United States of composite insulators using the second power. But with the run-time and run the increasing number of composite insulators failure information is gradually increasing. According to incomplete statistics, as of 1998, 15 cases occurred Breakdown interface in the east, north China, Guangdong, east, north region flashover accident occurred 23 cases. Obviously, at the same time improving the formulation and manufacturing process, improve the quality of composite insulators, to carry out targeted studies run of composite insulators detection technology has great significance for the protection of the safe operation of the grid. Currently running composite insulators detection techniques are:

Direct observation method

    Currently composite insulators for external physical defects most commonly used method is direct observation method, which uses binoculars to observe at the tower to discover common surface defects such as jacket, sheds, fittings and other parts of presence of cracks, with or without electrical erosion, powder, trackings, etc., if the above phenomenon should immediately replace insulators. But the ground was observed unreliable, the need to detect and difficult to find a plethora of failures such as dendritic channels within the insulation and the like.

Ultraviolet imaging

    Small but stable surface partial discharges can cause composite insulators umbrella skirt and jacket forming carbonized channels or electrical erosion. When the insulator surface carbonation channel, its life will be greatly reduced, or even breakdown in the short term. Studies using electron ultraviolet detectors can detect carbonation live channel composite insulators and electrical erosion surface formed due to the partial discharge, the principle is: partial discharge process complex will emit ultraviolet rays charged particles, formed when the insulator surface conductive carbonized channel, Partial Discharge intensified. Inadequacies of this approach is to require at night, is at ambient operating temperature; additional requirements to detect partial discharge is occurring, which requires testing should be in a high humidity environment even be rain. However, the test results susceptible viewing angle, but also more expensive testing equipment.

Infrared imaging

    Infrared imaging can detect partial discharge, leakage current flow resistance loss dielectric loss or the like over the insulating material insulator when local temperature rise caused, can be used for online testing. SVA Group Foshan power supply branch of a large number of composite insulators run infrared thermal imaging temperature survey found that: Where there is significant local hot spots insulators, high voltage insulator which is too hot to end the silicone rubber surface were significantly black, powder, brittle, hydrophobic basic loss, and some have a lot of small cracks or even serious damage; hot spots to the high voltage side of the section can not withstand the power frequency voltage withstand test or steep wave impulse test, known hot spots for the location of partial discharge within insulating interfaces progress ʱ?? High cost and measurement instruments subject to sunlight, wind, humidity, ambient temperature, and some of the effects can cause dramatic changes in the insulator surface temperature factor is the inadequacy of infrared imaging method.

Ultrasonic method

    Tsinghua University studied by ultrasonic method to detect cracks composite insulators mandrel. The implementation is based on ultrasonic testing ultrasonic occur in one medium into another medium from a propagation process at the interface of two media of reflection, refraction and mode conversion principle, ultrasonic generator start pulse emitted into the insulator media, when the insulator When there is a crack, a crack appeared in the reflected wave on the time axis, the defect wave on the time axis to determine the size and location of defects in the insulator case. Simple, safe and reliable anti-interference ability and other advantages of composite insulators mechanical defects detected by ultrasound. But because of its presence coupling, attenuation and ultrasound transducer performance issues on the remote telemetry is not yet a major breakthrough, not suitable for field testing, and is mainly used for production line testing and laboratory identification.

Electric field distribution law

    There are a variety of composite insulator interface, now that, because composite insulator metal tip at the bad seal moisture into the interior, causing electrical interface with the sheath along the mandrel or mandrel internal defects caused by the development of carbon composite insulators mark is the most also the most prone to the risk of failure. Steep wave test can detect insulation defects within the composite insulators, but the method can not achieve on-site online testing. The electric field distribution method available online within the insulation defect detection of composite insulators, and this method is relatively simple instruments, weather and other external environmental requirements low. Curve running composite insulators under normal conditions along the electric field strength and potential of the axial insulator is smooth. When the insulator continuity defect exists, where the potential becomes a constant, so the electric field strength will suddenly reduce the electric field distribution curve is no longer smooth, but there is distortion in the appropriate position, intermediate sinking, rise ends. Therefore, measuring the axial composite insulator strings electric field distribution within the insulator can find the continuity of insulation failure.

Hydrophobic detection method

    Currently, water repellency measuring method is suitable for the scene is mainly the Swedish Transmission Research Institute proposed water classification method. This method of composite insulators hydrophobic surface is divided into seven and gives classification criterion and standard image, HC-1 level and the HC-7 the level, corresponding to the water repellency of the strongest and the worst (ie, fully hydrophilic) state. Experiments with ordinary watering can to spray mist test surface was observed in the distribution of the water surface of the sample, compared to the standard classification criterion and pictures, draw the insulator surface hydrophobic condition. Defective sprinkler staging of a bigger dependence on subjective judgment. In recent years, the development of digital imaging technology and computer image processing technology for people to be more objective and accurate evaluation of surface hydrophobicity of composite insulators provides a new path. Swedish researchers composite insulator samples of artificial aging by measuring the level of water repellency spray fractionation, while shooting digital gray image after the insulator surface water. The use of computer image processing technology to extract from a large number of digital grayscale image and a function value HC grade math functions were monotonic relationship (named hydrophobic indicator function), thereby to obtain a hydrophobic insulator rating by hydrophobic indicator function. However, the study only remain in the laboratory stage, the lack of analysis of complex surfaces in complex situations; although on-site online test to predict the feasibility of doing, but did not put into practice. Currently, the North China Electric Power University (Beijing) High Voltage and Electromagnetic Research Institute is engaged in research of composite insulators compatible surface hydrophobicity line detection method based on water classification method and digital image processing technology and has achieved initial results, the entire project is expected in the 2005 first quarter.

Leakage current measurement

    Leakage current measurement method is the use of the principle of current leakage along the surface is formed in the insulator by draining the ground side card or a current sensor, on-line real-time measurement of the leakage current, by the signal processing unit calculates various statistical values of the leakage current over a period of time (e.g., peak to average , peak maximum or high current pulses), wireless transmission and wired transmission through the combination of the transmission of data to the data terminal, use of expert knowledge and self-learning algorithm to conduct a comprehensive analysis of the three knowledge of insulators contamination situation assess and forecast, and provide a scientific basis for the realization of condition-based maintenance. For composite insulators, because of its unique water-repellent and water-repellent mobility, so when wet insulator, at any one moment only to participate in conducting all the filth that has been dissolved without the loss of part, called the effective contamination. Thus, along the surface of composite insulators leakage current and valid Contamination related, but also has a relationship with hydrophobic. In addition, the insulator leakage current and voltage levels, insulators model, insulators number of pieces, the ambient temperature, humidity and other factors are also related. Research and application of this method is currently surviving in the larger dispute.