Application fields of far infrared thermometer

 After the current is passed through the electrical equipment, the temperature of the equipment will change, and its heat generation is proportional to the square of the current passed through; the temperature change of the bearings of rotating electrical equipment and mechanical equipment is closely related to the cooling medium, sliding friction and rolling friction... Any type of equipment failure is mostly manifested in the form of temperature change. By detecting the change in equipment temperature, timely judging and discovering whether the equipment has abnormalities and failures, it is of great significance to improve the reliability of equipment operation and extend the service life of the equipment, as well as to avoid equipment damage and personal injury. As we all know, the traditional equipment patrol temperature measurement method is to use mercury thermometers and alcohol (kerosene) thermometers. Mercury thermometers are greatly interfered by electromagnetic fields, and alcohol (kerosene) thermometers have very large errors when measuring equipment with higher temperatures. Therefore, the new equipment temperature measurement tool-far-infrared thermometer has been widely used.

 2 Application status of new far-infrared temperature measurement technology

 Far infrared temperature measurement technology is a new type of non-contact testing technology introduced from Europe and the United States in recent years, and has been widely adopted in the power industry. Far infrared temperature measurement technology is mainly used in power plants and substations to measure the temperature of electrical equipment, that is, to measure the heating and overload conditions of electrical equipment when current is passed through, the overheating of disconnectors and circuit breakers and metal connection parts, and the overheating of cable heads. However, it is rarely used to measure the bearing temperature of rotating equipment, whether sealed containers are leaking, detect steam-water separators, and find insulation faults in process pipelines or other insulation processes. In my work, I have encountered several typical and representative equipment failures discovered by measuring the temperature of non-current-passing parts of the equipment.

 3 Practical application examples

 In May 2003, a large steam turbine generator set in a certain factory was connected to the grid after overhaul. The vacuum of the steam turbine condenser could not be adjusted to the standard data for a long time, which affected the load of the set, and the thermal pipeline was oxidized and corroded, which would affect the life of the equipment. After checking the thermal system many times, the on-duty personnel did not find the fault. They looked through the relevant data of the overhaul of the set, and checked and measured all the operating equipment replaced during the overhaul with an infrared thermometer one by one. After measuring the front, rear, top, bottom, left and right temperatures of the condenser air valve that should be fully opened during normal operation of the set, it was found that the condenser air valve was not fully opened, resulting in a long-term low vacuum and high dissolved oxygen in the steam turbine! Immediately fully open the valve, the dissolved oxygen of the set immediately dropped to 8~9 micrograms, and ≤10 micrograms at the rated load of the set, meeting the normal operation requirements of the set. This measurement shows that the infrared thermometer plays an important reference role in checking the opening degree of the valve.

　　In June 2003, the operating duty personnel found during the inspection that the temperature of the fastening bolts between the bell cover and the base of the SSPB-240000/220 main transformer on the high voltage side was as high as 325℃ (the temperature of the four adjacent bolts was also about 120℃), and the temperature of the remaining bolts was the same as the temperature of the transformer bell cover flange, about 60℃. At that time, the unit was rated at 200,000 kilowatts, and the load was reduced to 170,000 kilowatts. The temperature of the overheated bolts dropped from 325℃ to 260℃. Analysis shows that the induced current generated by the transformer leakage magnetic field in the bell cover was unevenly discharged through the bolts, resulting in excessive current in some bolts. Loose bolts and poor contact between bolts and flanges will also cause overheating of the bolts. Re-tighten the bolts and bridge the short-circuit ring (or short-circuit flat iron) on the bolts with more serious heating to increase the heat dissipation of the bolts and shunt the temperature to 60℃. Otherwise, the rubber seal of the main transformer oil tank will cause local rapid deterioration and oil leakage.

　　A 300,000-kilowatt water-hydrogen-cooled steam turbine generator in a power plant has only undergone one major overhaul since it was put into operation. Shortly after a minor overhaul, the carbon brushes on the inner ring of the generator collector ring (on the generator side) were severely worn and replaced in batches for several consecutive shifts. At the same time, it was found that the brush holder of the generator collector ring was seriously contaminated with oil. The infrared thermometer detected that the temperature of the contact part between the inner ring surface of the collector ring and the carbon brush was as high as 230℃~360℃, and the temperature of the outer ring of the collector ring on the exciter side was normally 60℃~70℃. After the unit load dropped to 200,000 kilowatts, there was still no sign of the collector ring temperature falling back. It was initially judged that it was not due to electromagnetic factors. No sparks were seen between the carbon brush and the collector ring, and the operation was stable without excessive vibration. Mechanical vibration failures were also ruled out. Further inspection found that there was an oil pipe rupture between the outer side of the collector ring cover and the generator. The lubricating oil that flowed out flowed into the gap of the base of the collector ring cover and was sucked in and contaminated the inner ring of the collector ring due to the negative pressure, while the outer ring on one side was not affected. After shutdown treatment and coating the collector ring surface with industrial lubricant vaseline, the unit started and ran normally at 60℃~70℃.

 4 Application fields of far infrared temperature measurement technology

 The method of measuring overheating at the joints of metal conductors has been generally mastered. However, the method of measuring overheating of non-current-carrying conductors has not been taken seriously. Local overheating of the enclosed busbar of a large generator; overheating of the flange bolts of the bell jar of a large-capacity transformer; whether the sealed container is leaking; detecting the steam-water separator; finding the insulation failure in the process pipeline or other insulation process, etc. are almost forgotten. Far-infrared temperature measurement equipment has been widely used in various production positions. Engineers should jump out of the thinking circle that wherever the current is passed, there may be heat, so they should check there. The iron core failure of the motor; the failure of the high-voltage bushing of the transformer, the blockage of the oil pipeline; the failure of the lightning arrester due to moisture and heating; the insulation aging failure of the capacitor and the degradation failure of the cable insulation, etc., can all be verified by far-infrared measurement. In accordance with the principle of "no one can be left behind", all equipment should be checked with far-infrared measurement equipment, so as to ensure that the hidden dangers of the equipment are eliminated in the bud.