The principle of infrared temperature measurement technology is based on the fact that all objects whose temperature is higher than absolute zero in the natural world radiate infrared rays every moment. This type of infrared radiation carries characteristic information of objects. This is to use infrared technology to distinguish various measured The target's temperature level and heat distribution field provide an objective basis, and the object represents the change of thermodynamic temperature, resulting in a corresponding change in the heating power of the object. The heat generated by the object emits infrared radiation and forms a certain surface temperature distribution field around the object. This temperature distribution field depends on the thermal physics of the physical material, that is, the thermal diffusion inside the object and the surface temperature of the object and the outside world. Temperature heat exchange. At present, most electric power users use low-voltage, high-current electric equipment. Once the electric equipment fails, it can easily cause high temperatures. At the same time, poor contact of electrical equipment can cause high temperatures, ignition, arcing, and can easily become a fire ignition source. Similar to this dangerous temperature and hidden dangers, it is often difficult to find u infrared temperature measurement diagnostic methods are mainly surface temperature judgment method, relative Temperature difference judgment method, similar comparison method, thermogram analysis method, file analysis method. The surface temperature judgment method is a method commonly used by current production test personnel. This method is based on the measured surface temperature value of the equipment and compares the relevant regulations. Where the temperature (or temperature rise) exceeds the standard, the temperature of the equipment may exceed the standard. The importance of equipment, equipment and mechanical stress to determine the nature of equipment defects, and most production personnel are often simply based on whether the device is heating and the absolute temperature of the heating to subjectively judge whether the equipment is in the degree of defects and defects, so this type of The method is too subjective and decisive, and the lack of reliability of the criteria often leads to misjudgments. The author personally believes that relative temperature difference judgment method and similar comparison method are more objective and correct in on-site judgment.
The relative temperature difference method, as the name suggests, is based on the relative temperature difference method u. The relative temperature difference is the percentage of the ratio of the temperature difference between two corresponding measurement points to the temperature increase of the hot spot.
Temperature rise The difference between the surface temperature of the measured object and the surface temperature of the reference surface measured with the same tester.
Temperature difference The temperature difference between different measured objects or different parts of the same measured object that are measured in succession by the same tester.
The ambient temperature reference body The object used to collect the ambient temperature is called the ambient temperature reference body. It may not have the real ambient temperature at the time, but it has similar physical properties to the measured object and is in a similar environment to the measured object. For example, for LWE6-110 oil-immersed current transformers, if the top metal sheet is measured to generate heat, then the reference body for the ambient temperature can select similar metal parts or metal parts with the same material, but not ceramics or other choices. Materials such as metal.
For the current-heating type equipment, if it is found that the thermal conductivity of the diversion part of the equipment is abnormal, calculate the relative temperature difference according to formula (1) after accurate temperature measurement, and determine the nature of the equipment defect according to the provisions in the above table. When the temperature rise of the hot spot is less than 10K, it is not appropriate to determine the nature of the equipment defect as described above. For equipment with small load rate and small temperature rise but large relative temperature difference, if there is a condition to change the load rate, the load current may be increased and then retested to determine the nature of the equipment defect. When such retesting cannot be carried out, it can be tentatively determined to be a general defect, and attention should be paid to monitoring the comparison between the same type and the equipment of the same type. Similar comparison methods can be divided into current-heating devices and voltage-heating devices. Comparison u In the same electrical circuit, when the three-phase current is symmetrical and the three-phase (or two-phase) devices are the same, compare three phases (or two phases). The temperature rise value of the corresponding parts of the current heating type (such as current transformers) can determine whether the equipment is normal. If three-phase equipment is abnormal at the same time, it can be compared with the same equipment in the same circuit.
When the three-phase load current is asymmetric, the influence of the load current should be considered. For the same type of voltage-heat-type devices (such as arresters) can be based on the difference in the corresponding point temperature rise to determine whether the device is normal u voltage-heat-type equipment, the defect should be used to allow temperature rise or determine the basis of the same allowable temperature difference u In the general case, when the temperature difference of the same type exceeds 30% of the allowable temperature rise value, it shall be determined as a major defect. When the three-phase voltage is asymmetric, the influence of the working voltage shall be considered.
The thermogram analysis method judges whether the equipment is normal or not based on the difference in the thermograms of the same equipment in the normal state and the abnormal state. The archival analysis rule is to analyze the detection data (such as temperature rise, relative temperature difference and thermogram) of the same device in different periods to find out the change trend and rate of change of the heating parameters of the equipment to judge whether the equipment is normal or not.
In the actual operation of the job site, we must first ensure the accuracy of the device temperature test in order to carry out subsequent data judgments, and to do accurate temperature measurement should pay attention to the following matters: Select different ambient temperature reference body for different detection targets; When the heating point of the equipment, the corresponding point of the normal phase and the ambient temperature refer to the temperature value of the body, the same instrument should be used for successive measurement; the emissivity of the measured object should be correctly selected; 4 when comparing for the same type, it is necessary to keep the instrument and each corresponding measuring point The distance is the same and the orientation is the same. 5 Correctly input the compensation parameters such as atmospheric temperature, relative humidity, and measurement distance, and select the appropriate temperature measurement range; detect from different bearings, find the temperature value of the hottest point, and record the actual load of the abnormal equipment. Current and heating phases, normal phase and ambient temperature refer to the temperature of the body.
After obtaining the accurate temperature value of the equipment, if the temperature of the equipment is abnormal, a preliminary judgment shall be made on the basis of the surface temperature judgment method in combination with the relative temperature difference judgment method and the similar comparison method. The preliminary conclusions shall be obtained on the spot. The graph analysis method and the archive analysis method were compared on multiple sides and the final conclusions were drawn on site. The three properties of the defects are listed in the above table: General defects, which are defects that have little effect on recent safe operations. Can be included in the annual and quarterly maintenance plan to eliminate; major defects, refers to the defects are relatively large, but the equipment can still continue to operate in short-term security defects. Should be eliminated in the short-term elimination should be strengthened before the monitoring; emergency defects, refers to the severity of the equipment has been unable to run safely, may lead to accidents at any time or endanger personal safety defects u must be eliminated as soon as possible or take the necessary safety measures to deal with. We must be cautious when we make conclusions on the defects. The misjudgment of the conclusions may lead to unnecessary power outages to the equipment, affect the reliability of the power supply or lead to the missed inspection of the equipment, which may lead to personnel liability equipment accidents or even power grid accidents or personal injury or death.
Conclusion: We must make conclusions through repeated analysis, file analysis, and other methods in combination with the comparison and analysis of equipment abnormalities reflected by infrared diagnostic thermometry. This is consistent with the normal development of our state maintenance work and the advancement of quality services. The requirements can realize the maintenance goal of "requiring compulsory repairs and repairs to be repaired" in the true sense, so as to ensure the gradual increase of equipment maintenance effects with limited manpower and material resources, ensure the safe and reliable operation of the equipment, and ensure the safe and stable operation of the power grid to create a true The "strong, strong, excellent assets, excellent service, and outstanding performance" are the "one strong and three excellent" power grid enterprises.
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