Correct use of infrared thermometer to diagnose equipment faults
The core issue of infrared diagnosis for equipment faults recommended by infrared thermometers is to accurately obtain the temperature distribution of the tested equipment or the temperature value and temperature rise of the fault related points. This temperature information is not only a basis for determining whether the equipment is faulty, but also an objective basis for determining the fault attribute, location, and severity. Therefore, the calculation and reasonable correction of the temperature of the relevant parts of the tested equipment fault is a key link to improve the accuracy of the surface temperature of the testing equipment. However, when conducting infrared detection of equipment on site, due to changes in detection conditions and environmental influences, the same equipment may obtain different results due to different detection conditions. Therefore, in order to improve the accuracy of infrared detection, it is necessary to take corresponding countermeasures and measures during the on-site detection process or the analysis and processing of detection results, choose good detection conditions, or make reasonable corrections to the on-site detection results.
The impact of electrical equipment operation status:
Electrical equipment faults are generally heating faults caused by current effects (conductive circuit faults - heating power is proportional to the square of the load current value), and heating faults caused by voltage effects (insulation medium faults - heating power is proportional to the square of the operating voltage). Therefore, the operating voltage and load current of the equipment will directly affect the effectiveness of infrared detection and fault diagnosis. The increase in leakage current can cause uneven voltage in some high-voltage equipment parts. If there is no load operation or the load is very low, it will make the equipment malfunction heating less obvious, and even if there is a more serious malfunction, it is impossible to be exposed in the form of characteristic thermal anomalies. Only when the equipment is operating at rated voltage and the load is higher, the heating and temperature rise become more severe, and the characteristic thermal anomalies at the fault point are also exposed more clearly.
In this way, when conducting infrared detection, in order to achieve reliable detection results, it is necessary to ensure that the equipment operates at rated voltage and full load as much as possible. Even if continuous full load operation cannot be achieved, an operation plan should be developed to allow the equipment to run at full load for a period of time before and during the detection process, allowing sufficient heating time for the faulty part of the equipment and ensuring stable temperature rise on its surface. When conducting infrared diagnosis of electrical equipment faults, the fault judgment standard is often based on the temperature rise of the equipment at the rated current. Therefore, when the actual operating current during detection is less than the rated current, the actual measured temperature rise at the equipment fault point on site should be converted into the temperature rise of the rated current.
Equipment surface infrared measuring instruments obtain equipment temperature information by measuring the infrared radiation power on the surface of electrical equipment. And when the infrared diagnostic instrument receives the same infrared radiation power from the target, different detection results will be obtained due to the different surface emissivity of the target. That is to say, with the same radiation power, the lower the emissivity, the higher the temperature will be displayed. The surface emissivity of an object mainly depends on the material properties and surface state (such as surface oxidation, coating material, roughness, and pollution state).
Therefore, in order to accurately measure the temperature of electrical equipment using infrared measuring instruments, it is necessary to know the emissivity value of the tested target and input this value as an important parameter for calculating temperature into the computer or adjust the infrared measuring instrument ε Correct the value to correct the emissivity of the measured temperature output value. Two strategies to eliminate the impact of emissivity on detection results: when using an infrared thermometer for measurement, the emissivity should be corrected by checking the emissivity value on the surface of the tested equipment components, in order to obtain reliable temperature measurement results and improve the reliability of detection; For equipment components with frequent faults in infrared detection, in order to ensure good comparability of detection results, the method of applying appropriate paint can be used to increase and stabilize their emissivity values, in order to obtain the true temperature of the surface of the tested equipment.
The impact of atmospheric attenuation:
The infrared radiation energy on the surface of the tested electrical equipment is transmitted to the infrared detection instrument through the atmosphere, which is affected by the absorption and attenuation of gas molecules such as water vapor, carbon dioxide, and carbon monoxide in the atmospheric combination, as well as the scattering and attenuation of suspended particles in the air.
