In the stable operation of low-voltage overhead lines, pressed polymer insulators play a key role in insulation support. Accurately determining their health status is related to the safety of the power grid. This is inseparable from a series of scientific and effective testing methods.
Appearance inspection is a basic and intuitive method. Operation and maintenance personnel need to conduct regular inspections to check whether the surface of the insulator is damaged or cracked. Fine cracks may expand during long-term operation and weaken the insulation performance; pay attention to whether there are traces of discharge. Black burnt marks indicate that local discharge has occurred and the insulation has been partially damaged; observe whether there is dirt, dust, and bird droppings accumulation. Severe dirt will form a conductive channel and reduce the insulation resistance. With the help of auxiliary tools such as telescopes and drone aerial photography, the appearance of high-altitude insulators can be checked more efficiently.
Insulation resistance test is the core detection method. Use a professional insulation resistance meter to regularly measure the insulation resistance between the two poles of the insulator and between the poles and the ground. The resistance value of a normally operating pressed polymer insulator should be far above the specified threshold. If the reading is low or even close to zero, it indicates that the insulation material is damp, aged or has been broken down. The test should be carried out in dry and sunny weather, avoiding foggy and rainy days, to ensure that the data truly reflects the insulation condition of the insulator. The resistance data of insulators installed in different line sections and batches should be recorded in detail for comparison and analysis.
Partial discharge detection has high sensitivity and can detect early hidden dangers. Use ultrasonic partial discharge detectors or ultra-high frequency detection equipment to capture partial discharge signals caused by insulation defects inside the insulator. Once abnormal discharge frequency and amplitude are detected, it means that there are defects such as air gaps and impurities inside, resulting in uneven electric field distribution, and discharge continuously erodes the insulation body. The online real-time monitoring system can track around the clock, and combined with intelligent algorithms, timely warnings allow the operation and maintenance team to quickly locate the problem insulator.
In addition, infrared thermal imaging detection is also indispensable. If the insulators in operation have faults such as poor contact or excessive local resistance, abnormal hot spots will be generated due to the thermal effect of current. Thermal imagers can accurately capture temperature difference changes and visually present potential faults, helping operation and maintenance personnel to cool down and eliminate faults in a timely manner, comprehensively ensuring the healthy service of pressed polymer insulators and maintaining reliable power supply for the low-voltage power grid.
