Development of an endoscopic temperature field monitoring system based on infrared imaging fiber bundle under specific gas atmospheres

• Proposed a novel structure of endoscopic temperature field monitoring system for electrical equipment; • Acquired temperature-response mapping data under infrared high-absorption atmosphere and closed-background radiation conditions; • Even after the attenuation of target thermal radiation energy through optical fiber bundles, the system’s temperature measurement deviation remains consistent with that of traditional high-transmittance infrared thermal imagers. To evaluate the operational status of gas-insulated high-voltage power equipment, it is essential to acquire temperature distribution within its internal enclosure. From an engineering perspective, the monitoring system must preserve insulation performance while exhibiting strong resistance to electromagnetic interference and high environmental adaptability. This paper proposes an endoscopic temperature field monitoring system based on infrared imaging fiber bundle, specifically designed for high-pressure, infrared-absorbing gas environments. The system’s structural design, operating principles, and calibration procedures for establishing the mapping between target temperature and sensor response are systematically presented. Focusing on the monitoring performance under specific temperature fields, a comprehensive analysis is conducted from key aspects including thermal radiation from the target surface, infrared absorption by high-pressure gas, photoelectric signal transmission, and thermal image processing. Corresponding temperature retrieval methods and performance assurance measures are proposed. The results demonstrate that the developed monitoring system maintains stable performance under specific gas atmospheres, achieving a temperature measurement accuracy better than ± 2 °C and a normalized non-uniformity below 0.002 for the response values of signals corresponding to the fiber core. These findings provide guidance for optimizing insulation structures and monitoring internal temperature fields and hotspots in gas-insulated high-voltage power equipment, offering a potential breakthrough in addressing the long-standing challenge of three-dimensional temperature field monitoring.