Rarely are far-infrared thermometers used for equipment inspection.
1 Limitations of traditional temperature measurement
After the electrical equipment is connected to the current, the temperature of the equipment will change, and its calorific value is proportional to the square of the current; the temperature change of the bearing of the rotating electrical equipment and mechanical equipment is closely related to the cooling medium, sliding friction and rolling friction... Equipment Any type of failure is mostly manifested in the form of temperature changes. By detecting the temperature change of the equipment, judging and discovering whether the equipment is abnormal or fault in time is of great significance to improve the reliability of the equipment operation, prolong the service life of the equipment, and avoid equipment damage and personal injury. As we all know, the traditional method of measuring equipment inspection temperature is to use mercury thermometer and alcohol (kerosene) thermometer. Therefore, a new equipment temperature measurement tool - far infrared thermometer has been widely used.
2 Application status of new technology of far infrared temperature measurement
Far-infrared temperature measurement technology is a new type of non-contact testing technology introduced from European and American countries in recent years, and it has been widely used 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, the fault overheating of the isolating switch and the breaker fracture and the metal connection part, and the overheating fault of the cable head. etc. However, it is rarely used to measure the bearing temperature of rotating equipment, whether the sealed container is leaking, detect the steam separator, find the insulation fault in the process pipeline or other insulation process, etc. In the author's work, I encountered several cases of equipment failures that were typical and representative by measuring the temperature of the non-flow part of the equipment.
3 Practical application examples
In May 2003, a large steam turbine generator unit in a certain factory was connected to the grid after the unit was overhauled. The vacuum of the steam turbine condenser was not adjusted to the specification data for a long time, the unit load was affected, and the thermal pipeline was oxidized and corroded, which would affect the life of the equipment. The personnel on duty did not find the fault after checking the thermal system for many times. They read the relevant information of the overhaul of the unit, and checked and measured all the operating equipment replaced during the overhaul with an infrared thermometer one by one. When the unit is in normal operation, it should be completely After the temperature of the front, back, up, down, left and right of the opened condenser air door valve, it was found that the condenser air door was not fully opened, resulting in low vacuum and high dissolved oxygen in the steam turbine for a long time! Open the air valve completely immediately valve, the dissolved oxygen of the unit was immediately reduced to 8~9 micrograms, and it was ≤10 micrograms at the rated load of the unit, which met the normal operation requirements of the unit. This measurement shows that the infrared thermometer is an important reference for checking the opening degree of the valve.
In June 2003, the patrol inspection of the operation duty personnel found that the temperature of the fastening bolts between the bell jar and the base on the side of the high voltage side of the SSPB-240000/220 main transformer in operation was as high as 325°C (the temperature of the four adjacent bolts also reached 120°C) ℃), and the temperature of the rest of the bolts is the same as the temperature of the transformer bell jar flange, about 60 ℃. The analysis shows that the induction current generated by the transformer magnetic flux leakage in the bell jar is unevenly discharged through the bolts, and the local bolt current is too large, the bolts are loose, and the bolts are in contact with the flange, which will also cause the bolts to overheat. Re-tighten the bolts, and bridge the short-circuit ring (or short-circuit flat iron) with the bolts with severe heat to increase the heat dissipation and shunt of the bolts and reduce the temperature to 60°C. Otherwise, the rubber gasket of the main transformer oil tank will deteriorate rapidly and cause oil leakage.
A 300,000-kilowatt water-hydrogen-hydrogen-cooled turbogenerator in a power plant has only undergone one overhaul after it was put into operation.
Shortly after a minor repair, the carbon brushes on the inner ring of the generator collector ring (near the generator side) were severely worn, and they were replaced in batches for multiple consecutive shifts. The infrared thermometer found that the temperature of the inner ring surface of the collector ring and the contact part of the carbon brush was as high as 230°C~360°C, the temperature of the outer ring of the collector ring on the side of the exciter was normally 60°C~70°C, and the unit load dropped to 20°C. After 10,000 kilowatts, there is still no sign that the temperature of the collector ring has dropped, and it is preliminarily judged that the reason is non-electromagnetic. No sparks can be seen between the carbon brush and the collector ring, and the operation is stable, and there is no vibration exceeding the standard, and the failure of the mechanical vibration has also been ruled out. Further inspection found that there is a broken oil pipe between the outer side of the collector ring cover and the generator, and the outflow The lubricating oil flows into the base gap of the collector ring cover and is sucked by the negative pressure and pollutes the inner ring of the collector ring, while the outer ring is not affected on one side. After shutting down and coating the surface of the collector ring with industrial lubricating vaseline and other measures, the unit starts to operate at a normal temperature of 60°C to 70°C.
4 Application fields of far infrared temperature measurement technology
Methods for measuring overheating at metallic conductor joints are generally known. However, the method of measuring the overheating of non-current-carrying conductors has not been taken seriously. The closed bus bar of large generators is locally overheated; the flange bolts of large-capacity transformer bell jars are overheated; whether the sealed container is leaking; detecting the steam-water separator; Insulation failures, etc. are all but forgotten. Far-infrared temperature measuring equipment has been widely used in various production positions. Engineers want to jump out of the strange circle of thinking where there may be heat where the current is connected. The iron core fault of the motor; the fault of the high voltage bushing of the transformer, the blockage fault of the oil pipeline; the fault of the arrester caused by moisture and heat; the fault of the insulation aging of the capacitor and the deterioration of the cable insulation, etc. In line with the principle of "nothing less", all equipment should be inspected with far-infrared measuring equipment, so as to ensure that hidden dangers of equipment are eliminated in the bud.
