The composite insulator product consists of three parts: glass fiber epoxy resin pull rod, silicon rubber umbrella skirt and hardware. The silicone rubber umbrella skirt adopts an integral injection molding process, which solves the key problem that affects the reliability of composite insulators and interface electrical breakdown. Its defect detection technology is as follows:
At present, the most commonly used method for the external physical defects of composite insulator is the direct observation method, that is, using binoculars to observe under the tower to find common surface defects such as sheaths, umbrella skirts, fittings, whether there are cracks, and whether there are electrical corrosion damage, chalking, traces of leakage, etc., if the above phenomenon occurs, replace the insulator immediately. However, the ground observation is not reliable enough, and it is necessary to climb the tower for inspection and it is difficult to find internal insulation faults such as dendritic channels.
Small but stable surface partial discharges can cause the formation of carbonized channels or electrical corrosion damage to the umbrella skirt and sheath of the composite insulator. When a carbonized channel is formed on the surface of the insulator, its service life will be greatly reduced, and even breakdown in a short time. The electronic ultraviolet optical flaw detector can be used to detect the carbonized channels and electrical corrosion damage formed on the surface of the composite insulator due to partial discharge. In addition, it is required that the partial discharge is occurring during the detection, which requires the detection to be performed in an environment with high humidity or even rain.
The infrared imaging method can detect the local temperature rise of the insulator caused by the partial discharge, the dielectric loss or the resistance loss when the leakage current flows through the insulating material, and it can be used for online detection.
The realization of ultrasonic detection is based on the principle that reflection, refraction and mode conversion of ultrasonic waves will occur at the interface of two media during the propagation process of ultrasonic waves from one medium to another. The ultrasonic generator emits an initial pulse into the insulator medium. When there is a crack, the reflected wave of the crack appears on the time axis, and the defect in the insulator can be judged by the size and position of the defect wave on the time axis. Ultrasonic detection of mechanical defects of composite insulators has the advantages of simple operation, safety and reliability, and strong anti-interference ability.
The electric field distribution method can detect the internal insulation defects of composite insulators online, and the instrument used in this method is relatively simple, and the requirements for the external environment such as weather are very low. When there is a continuity defect in the insulator, the potential at that place becomes a constant, so the electric field intensity will suddenly decrease, and the electric field distribution curve will no longer be smooth, but there will be distortion at the corresponding position, the middle sinking, and the two ends rising. Therefore, measuring the axial electric field distribution of the composite insulator string can find the internal insulation continuity fault of the insulator.
At present, the hydrophobicity testing method applicable to the field is mainly the water spray classification method proposed by the Swedish Power Transmission Institute. This method divides the hydrophobicity of the composite insulator surface into 7 grades and gives the classification criteria and standard pictures. HC-1 and HC-7 respectively correspond to the strongest and worst (ie completely hydrophilic) state of hydrophobicity.