Failure Diagnosis of Infrared Thermometers Correct Use
Recommended by the infrared thermometer equipment failure infrared diagnosis of the most core issues, the requirement to accurately obtain the temperature distribution of the device under test or fault-related point temperature values and temperature rise. This temperature information is not only the basis for determining the presence or absence of faults in the equipment, but also the objective basis for determining the fault attributes, location and severity. Therefore, the measured equipment failure-related parts of the temperature calculation and reasonable correction, is to improve the accuracy of the surface temperature of the detection equipment is a key link. However, in the field of infrared detection of equipment, due to changes in detection conditions and environmental impact, may lead to the same equipment due to different detection conditions, and get different results. Therefore, in order to improve the accuracy of infrared detection, it is necessary to take appropriate countermeasures and measures or select good detection conditions or reasonable corrections to the detection of the results of the field detection process or the analysis and processing of the results.
Which the impact of the operating state of electrical equipment:
Electrical equipment failures are generally current effect caused by the heating failure (conductive circuit failure - heating power is proportional to the square of the value of the load current), and voltage effect caused by the heating failure (insulation medium failure - heating power is proportional to the square of the operating voltage). Therefore, the magnitude of 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 parts of the high-voltage equipment. If there is no loaded operation or the load is very low, it will make the equipment fault heating is not obvious, even if there is a more serious fault, it is unlikely to be exposed by the characteristic thermal anomalies in the form of. Only when the equipment is operated at the rated voltage, and the higher the load, the more serious the heating and temperature rise, and the more obvious the characteristic thermal anomalies at the point of failure are exposed.
In this way, in the infrared detection, in order to be able to achieve reliable detection results, should try to ensure that the equipment in the rated voltage and full load operation, even if it can not be done continuously under full load operation, but also should be prepared for a running programme, so that in the detection of the pre-testing and the detection process, can let the equipment run under full load for a period of time, so that the equipment fault parts have enough time to heat up and ensure that the surface of the surface to achieve a stable temperature rise. Electrical equipment fault infrared diagnosis, fault judgement criteria is often based on the temperature rise of the equipment at rated current, so when the detection of the actual operating current is less than the rated current, it should be the site of the actual measurement of the equipment fault point temperature rise converted to the temperature rise of the rated current.
Equipment surface infrared measuring instrument are through the measurement of electrical equipment surface infrared radiation power, to obtain equipment temperature information. And in the case of infrared diagnostic instruments to receive the same infrared radiation power from the target, due to the different surface emissivity of the target, will get different detection results. That is to say, for the same radiant power, the lower the emissivity, the higher the temperature will be displayed. The surface emissivity of an object is mainly determined by the nature of the material and the surface condition (e.g. surface oxidisation, coating material, roughness and dirtiness, etc.).
Therefore, in order to apply infrared measuring instruments to accurately measure the temperature of electrical equipment, it is necessary to know the value of the emissivity of the inspected target, and enter the value into the computer as an important parameter for calculating the temperature or adjust the ε-correction value of the infrared measuring instrument in order to correct the emissivity of the measured temperature output value. Eliminate the impact of emissivity on the detection results of the two countermeasures: when using infrared thermometer for measurement, the emission to be corrected, find out the emissivity value of the surface of the measured equipment components emissivity correction, so as to obtain reliable temperature measurement results, improve the reliability of the detection; for infrared detection of fault-frequent equipment components, in order to make the detection results have a good comparability, you can use the method of laying the appropriate paint to Increase and stabilise the emissivity value, in order to obtain the real temperature of the surface of the equipment being tested.
The effect of atmospheric attenuation:
The measured surface of the electrical equipment infrared radiation energy, transmitted to the infrared detection instruments through the atmosphere, which will be subject to atmospheric combination of water vapour, carbon dioxide, carbon monoxide and other gases such as molecular absorption attenuation and airborne particles in the air scattered attenuation of the impact of the attenuation.
