Application—Infrared Thermal Imaging Detection of Substation Insulators

Infrared Thermal Imaging Detection of Substation Insulators

   Porcelain insulator strings have important applications in substations, power plants, and transmission lines. Not only are they required to have good mechanical properties, but also good electrical properties. Since the porcelain insulator string is subjected to long-term cold and heat changes, electromechanical load, mechanical stress, and atmospheric pollution during operation, defects such as insulation degradation, insulation breakdown, and flashover discharge will occur after long-term operation, which will bring major problems to the power grid. Safety hazards.

   In recent years, with the continuous progress of infrared thermal imaging technology and the improvement of infrared image processing methods, the detection of degraded insulators based on infrared thermal imaging technology has established a solid foundation. According to the voltage distribution of insulator strings under different environmental conditions, domestic and foreign scholars have conducted a lot of research on the identification of degraded insulators by infrared thermal imaging. The experimental results show that the detection humidity should be kept as close as possible to about 80%, which can improve the detection accuracy of zero-value insulators. Aiming at the problem of underreporting of degraded insulators in engineering practice, a calculation method of infrared detection blind zone based on Thevenin’s equivalent circuit method was proposed, and it was concluded that voltage distribution and temperature difference range are the two core factors that affect the size of the blind zone. Through the research on the heating mechanism of insulators and infrared thermal imaging technology, based on the low zero value in the project, the infrared spectra of the zero-value insulators at different positions in the insulator string are analyzed respectively. When the experimental insulator string contains severely contaminated insulators and in the case of a zero-value insulator, the thermal image spectrum is obviously different from the normal one. When the zero-value insulator in the insulator string is located at the high-voltage end, the infrared temperature measurement spectrum is characterized by the obvious temperature difference between adjacent normal insulators and the zero-value insulator.

Figure 1. Steel cap infrared thermal imaging temperature.

   This research analyzes the heating mechanism of porcelain insulators, effectively identifies zero-value insulators and contaminated insulators in the operating insulator string, demonstrates the effectiveness and practicability of infrared temperature measurement technology, and draws relevant conclusions to carry out infrared detection in actual engineering Identifying degraded insulators has guiding significance.

Figure 2. Infrared thermal imaging temperature of insulator.

   In this study, a voltage distribution model and an electrothermal conversion model were established. Through simulation calculations, field measurements, and high voltage tests, the following conclusions were drawn: 1) High voltage tests and infrared thermal imaging measurements showed that the voltage distribution and temperature distribution of the normal insulator string were not Symmetrical saddle shape and positive correlation. 2) The infrared thermal image of low-value porcelain insulators with high steel cap temperature is bright; the infrared thermal image of zero-value insulators with low steel cap temperature is dark; the infrared thermal image of contaminated insulators with higher disk temperature. The spectrum is bright tones.

Figure 3. Infrared thermal imaging temperature of insulator.

   3) The horizontal porcelain tensile insulator string bears strong mechanical stress for a long time, which will easily cause the first insulator on the high-voltage side to be easily degraded into low-value insulators; the vertical porcelain insulator string has a horizontal porcelain surface, which is easy to accumulate dirt, Degraded to dirty insulators. 4) The 220kV side of the main transformer adopts a single-strand tensile insulator string which is extremely easy to degrade, and it is recommended to replace all the double-strength tensile insulator strings. 5) For the degraded insulator string, regular live detection should be carried out to monitor the development of defects; if the number of degraded insulators in a single string of insulators exceeds 1/3, it should be repaired and replaced. 6) For substations in heavily polluted areas, live water flushing and infrared detection should be carried out regularly; the flashover situation should be observed and tracked during the initial rain and the rainy phase. If a large area flashover is found in the insulator string, accident handling and fault isolation should be taken.