Correctly use infrared thermometer to diagnose equipment faults
The core problem of infrared diagnosis of equipment faults recommended by infrared thermometers is to accurately obtain the temperature distribution of the equipment under test or the temperature values and temperature rise values of fault-related points. This temperature information is not only the basis for judging whether the equipment is faulty, but also the objective basis for judging the fault attribute, location, and severity. Therefore, the calculation and reasonable correction of the temperature of the fault-related parts of the equipment under test is a key link to improve the accuracy of the surface temperature of the detection equipment. However, when infrared detection of equipment is performed 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, corresponding countermeasures and measures must be taken during the on-site detection process or during the analysis and processing of the detection results, or good detection conditions must be selected, or reasonable corrections must be made to the on-site detection results.
Among them, the impact of the operating status of electrical equipment:
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). Proportional). Therefore, the operating voltage and load current of the equipment will directly affect the results of infrared detection and fault diagnosis. The increase in leakage current can cause uneven voltage in parts of high-voltage equipment. If there is no load operation or the load is very low, the heating of the equipment failure will not be obvious. Even if there is a serious failure, it will not be exposed in the form of characteristic thermal anomalies. Only when the equipment is operating at rated voltage and the load is greater, the heat generation and temperature rise will become more serious, and the characteristic thermal anomalies at the fault point will become more obvious.
In this way, when performing infrared detection, in order to obtain reliable detection results, we should try our best to ensure that the equipment operates at rated voltage and full load. Even if it cannot achieve continuous full load operation, an operation plan should be prepared to facilitate the detection during the detection. During the pre-operation and testing process, the equipment can be run at full load for a period of time, so that the faulty part of the equipment has enough time to heat up and ensure that its surface reaches a stable temperature rise. During infrared diagnosis of electrical equipment faults, the fault judgment standard is often based on the temperature rise of the equipment at rated current. Therefore, when the actual operating current during detection is less than the rated current, the temperature rise of the equipment fault point actually measured on site should be converted into the rated current. Temperature rise of 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 different surface emissivities of the target. In other words, for the same radiation power, the lower the emissivity, the higher the temperature will be displayed. Because the surface emissivity of an object is mainly determined by the material properties and surface state (such as surface oxidation, coating material, roughness and contamination state, etc.).
Therefore, in order to accurately measure the temperature of electrical equipment using an infrared measuring instrument, it is necessary to know the emissivity value of the target being inspected, and enter this value into the computer as an important parameter for calculating the temperature or adjust the ε correction value of the infrared measuring instrument so that the measured The temperature output value is corrected for emissivity. Two countermeasures to eliminate the impact of emissivity on the detection results: When using an infrared thermometer for measurement, the emission must be corrected, and the emissivity value of the surface of the component under test should be found and the emissivity corrected to obtain reliable temperature measurement. As a result, the reliability of detection is improved; for equipment components with frequent failures in infrared detection, in order to make the detection results have good comparability, the method of applying appropriate paint can be used to increase and stabilize the emissivity value, so as to obtain the measured The true temperature of the device surface.
Effects of Atmospheric Attenuation:
The infrared radiation energy on the surface of the electrical equipment under test is transmitted to the infrared detection instrument through the atmosphere, which will be affected by the absorption attenuation of gas molecules such as water vapor, carbon dioxide, and carbon monoxide in the atmospheric combination and the scattering attenuation of suspended particles in the air.
