Application—Design of Defect Detection System For Infrared Thermal Imaging Inspection Robot

Design of Defect Detection System For Infrared Thermal Imaging Inspection Robot

   Defects of transmission lines mainly include broken strands, loose strands, rust, defects, missing, displacement, lightning strikes, pollution, wear, corrosion, etc. In particular, defects and faults such as oxidation and corrosion of fittings on transmission lines, loose joints, aging, cracking and breakdown of insulators, seriously threaten the safe operation of power transmission systems. Electrical testing is a commonly used fault diagnosis method, but it is mostly destructive testing, which is not only costly, but also cannot be tested one by one, let alone online testing.

   Defect detection systems can be divided into image analysis systems and sensor analysis systems. The image analysis system uses visible light cameras, infrared thermal imaging cameras, ultraviolet cameras and other equipment to capture fault points in the operating environment. Image analysis systems can be divided into visible light analysis systems, infrared analysis systems, and ultraviolet analysis systems. The sensor analysis system can use laser radar, eddy current detector and other equipment. The laser radar is mainly used to collect the safe distance between the line and the ground and prevent the tree branch from hitting the line. The eddy current detector is installed on the walking mechanism of the robot and can detect the internal damage of the line that the robot walks.

Figure 1. Insulator sheet taken by inspection robot.

   Infrared thermal imaging is an advanced technology for non-contact, instantaneous visualization of thermal information, and accurate temperature measurement. Infrared thermal imaging camera can instantly reveal thermal faults. It is non-contact and far away from the tested equipment to ensure the safety of personnel and ensure that the original operating state of the equipment is not affected; it can directly display the heat distribution of the equipment in the form of images; automatically capture the highest, low temperature, And display the specific location and temperature value; large area rapid scanning and detection, saving time; equipped with powerful back-end analysis software, site workload is very small; wide temperature measurement range, high accuracy.

Figure 2. Insulators taken by inspection robots.

   During electrical discharge of high-voltage equipment, corona, flashover or arc will occur depending on the strength of the electric field. The electrons in the air continuously gain and release energy, and when the electrons release energy (that is, discharge), they emit ultraviolet rays. Ultraviolet imaging technology uses this principle to receive the ultraviolet signal generated when the device is discharged, and after processing, it overlaps with the visible light image and displays it on the screen of the instrument to determine the position and intensity of the corona, so as to further evaluate the operation of the device. The situation provides a more reliable basis.

   Visible light cameras can use continuous photography to obtain high-definition pictures. Visible light cameras are mainly used to collect structural geometric information of power transmission lines and towers. Thermal imaging cameras are mainly used to collect temperature information on power transmission lines. The ultraviolet camera is mainly used to collect the ionization and corona information of the transmission line, and analyze the defect of the line by analyzing the discharge phenomenon of the charged line.

Figure 3. Wire connection points taken by the inspection robot.

   In summary, the inspection robot can be equipped with visible light, infrared light, ultraviolet light defect analysis systems and sensor analysis systems (eddy current sensors, lidar, etc.) when inspecting high-voltage transmission lines. The working mode can adopt two kinds of offline mode and online mode. The offline mode is to record the whole inspection process. After the robot completes the inspection, it comes to the ground station from the ground line, and then takes out the data for defect analysis. The online mode means that the robot performs real-time defect analysis while driving, and reports the analysis results in real time. Online, real-time, fast and accurate is the development direction of the robot inspection defect analysis system.