Introduction to the correct use of infrared thermometer to diagnose equipment faults
The core problem of infrared diagnosis of equipment fault recommended by infrared thermometer requires accurate temperature distribution of the tested equipment or temperature values and temperature appreciation 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 the key link to improve the accuracy of the surface temperature of the testing equipment. However, when infrared detection of equipment is carried out in the field, the same equipment may get different results due to different detection conditions because of the changes of detection conditions and environment. Therefore, in order to improve the accuracy of infrared detection, it is necessary to take corresponding countermeasures and measures or choose good detection conditions or make reasonable corrections to the detection results in the process of on-site detection or the analysis and processing of the detection results.
Among them, the influence of the operation state of electrical equipment:
Electrical equipment faults are generally caused by current effect (conductive loop fault-heating power is proportional to the square of load current value) and voltage effect (insulation medium fault-heating power is proportional to the square of operating voltage). Therefore, the working voltage and load current of the equipment will directly affect the effect of infrared detection and fault diagnosis. The increase of leakage current can cause partial voltage unevenness of high-voltage equipment. If there is no load operation or the load is very low, the equipment fault will not be obvious, and even if there is a serious fault, it is impossible to expose it in the form of characteristic thermal anomaly. Only when the equipment operates at rated voltage and the load is greater, the heating and temperature rise will be more serious, and the characteristic thermal anomalies at the fault point will be more obvious.
In this way, in infrared detection, in order to obtain a reliable detection effect, we should try our best to ensure that the equipment runs at rated voltage and full load. Even if it can't run at full load continuously, we should work out an operation plan so that the equipment can run at full load for a period of time before and during detection, so that the faulty parts of the equipment can have enough heating time and the surface can reach a stable temperature rise. In 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 is less than the rated current during detection, the temperature rise at the fault point of the equipment actually measured on site should be converted into the temperature rise of the rated current.
The equipment surface infrared measuring instrument obtains the equipment temperature information by measuring the infrared radiation power on the surface of electrical equipment. And under the condition that the infrared diagnostic instrument receives the same infrared radiation power from the target, different detection results will be obtained because of the different surface emissivity of the target. That is to say, the lower the emissivity, the higher the temperature will be displayed with the same radiation power. Because 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, etc.).
Therefore, in order to accurately measure the temperature of electrical equipment by infrared measuring instrument, it is necessary to know the emissivity value of the detected object, and input 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 as to correct the emissivity of the measured temperature output value. Two countermeasures to eliminate the influence of emissivity on the detection results: when using infrared thermometer to measure, it is necessary to correct the emissivity, find out the emissivity value on the surface of the tested equipment parts, and correct the emissivity, so as to obtain reliable temperature measurement results and improve the reliability of detection; For the frequently-occurring equipment parts in infrared detection, in order to make the detection results have good comparability, the emissivity value can be increased and stabilized by applying appropriate paint, so as to obtain the real temperature of the surface of the tested equipment.
Effects of atmospheric attenuation:
The infrared radiation energy on the surface of the electrical equipment to be tested 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 atmosphere combination and the scattering attenuation of suspended particles in the air.
