What are the limitations of using infrared thermography for detecting faults in electrical equipment?

Infrared thermography, while a valuable tool for detecting thermal anomalies in electrical equipment, has several limitations that must be considered for accurate diagnosis. First, thermography only detects surface temperatures. It cannot "see" inside enclosures or components unless there is a direct line of sight to the heat source. This means that faults located deep within equipment, such as winding shorts in a motor, may not be detectable until the heat propagates to the surface. Second, the accuracy of thermographic measurements can be affected by emissivity, which is a material's ability to emit infrared radiation. Different materials have different emissivities, and if the emissivity is not accurately accounted for, the temperature readings can be inaccurate. Shiny or polished surfaces, for example, have low emissivity and can reflect infrared radiation from surrounding objects, leading to false readings. Third, ambient conditions, such as air temperature, humidity, and sunlight, can influence the temperature readings. High ambient temperatures can make it difficult to detect subtle temperature differences. Direct sunlight can heat up equipment surfaces, masking internal hot spots. Fourth, thermography is a qualitative rather than a quantitative technique. While it can identify hot spots, it may not provide precise temperature measurements or accurately quantify the severity of the fault. Additional diagnostic techniques, such as voltage and current measurements, may be needed to fully assess the problem. Fifth, thermography requires skilled and trained personnel to interpret the thermal images and diagnose faults correctly. Misinterpretation of thermal images can lead to incorrect diagnoses and unnecessary maintenance. Finally, some faults, such as intermittent connections or loose terminations that only heat up under specific load conditions, may be missed during a thermographic survey if the equipment is not operating under those conditions at the time of inspection. For instance, a loose connection in a panel might only heat up significantly when the circuit is heavily loaded; if inspected during a period of low demand, the problem could be overlooked.