Hydropower station has become one of the most important power generation modes in China, which occupies an important position in China's power industry and is also the most important power generation mode in China. Ensuring the normal operation of hydropower stations is related to the long-term stability of our people's lives and the smooth development of our socialist construction. Therefore, the relevant staff must ensure the normal operation of the hydro-generator set, maintain it regularly, repair it as soon as possible when problems are found, and do a good job in daily equipment management.
1 Overview of Hydrogenerator
The main function of hydro-generator is to convert the rotating mechanical energy of hydraulic turbine into electric energy, and its structure and performance play a vital role in the safe, stable and efficient operation of power station. Its composition mainly includes stator, rotor, frame, thrust bearing, guide bearing, cooler, brake and other parts. Hydrogenerators can be divided into horizontal and vertical types according to their arrangement. Horizontal hydro-generators are suitable for small and medium-sized turbines, tubular turbines and impulse turbines, while vertical generators are generally used for large and medium-sized units with medium and low speed. At the same time, according to the position of thrust bearing, its vertical generator can be divided into suspended generator and umbrella generator. A generator with a thrust bearing above the rotor is called a suspended generator, which is suitable for speeds above 100r/min. Generators with thrust bearings under the rotor are called umbrella generators, those without guide are called full umbrella generators, and those with upper guide are called semi-umbrella generators, which are suitable for speeds below 150r/min. The main factors affecting the operation of hydro-generator are mechanical vibration, electromagnetic vibration and hydraulic vibration. The interference force of mechanical vibration mainly comes from the unbalanced force and friction force of mechanical parts; The interference force of electromagnetic vibration mainly comes from the electromagnetic force of the generator electrical part; The interference force of hydraulic vibration comes from the vibration of water diversion system and hydraulic part of hydraulic turbine. Therefore, attention should be paid to the important interference caused by its influencing factors during the operation of the hydro-generator set, and attention should also be paid to the detection and inspection of its influencing factors during the maintenance process.
2 Common problems in the operation of hydro-generator sets
1) Stator winding operating temperature monitoring. Usually, the operating temperature of the stator winding is monitored by a thermometer. The manufacturer installs a resistance thermometer in the tank and detects the temperature of the equipment through the thermometer. The monitoring process is to bury a thermocouple with a special wire and test the temperature through the heat conduction of the thermocouple. The temperature measurement environment is generally rated, and the highest thermoelectric temperature of the winding is 30℃~40℃ higher than the temperature between the wire and the bar in the slot.
2) Insulation aging of stator winding. The insulation function of stator winding is very important, which can slow down mechanical aging, electrical aging and thermal aging. The three functions are not good, which will accelerate the aging speed of equipment and damage the long-term use of equipment. For mechanical aging, when enterprises solve this problem, most of them use epoxy conformal materials at both ends, reinforce them with glass tapes, put felt strips in the grooves, and wedge them tightly at both sides. This method can solve the urgent need, but after years of operation, its stability is still challenged, especially the wedge-shaped part, which is obviously loose and needs to be fixed again. For electrical aging, the key point is the anti-corona structure on the outer surface of insulator. The perfection of this structure for the end and groove needs to be improved, and the air removal inside the insulator has not achieved the ideal goal. For thermal aging, the detection of its temperature is mainly considered, and it should be noted that the temperature cannot exceed the highest value borne by insulators.
3) stator winding insulation pollution. At present, many hydro-generator sets will have dust accumulation, and the oil pollution caused by perennial use is also serious. The accumulation of dust and oil pollution have a great influence on the operation of equipment, and will also affect the heat dissipation of iron core, and even lead to fire accidents in serious cases. Usually in the maintenance process, it is purged with compressed air, or cleaned with brush, white cloth and solvent. The second cleaning method is easy to clean the equipment in place, and can not achieve the more basic cleaning purpose.
4) Generator fire extinguishing device. At present, most of the fire extinguishing devices used in China are water extinguishers, and most of the fire extinguishing equipment is manually operated. When the control equipment of the generator set trips, managers should immediately put out the fire when they find that the equipment smokes or smells of burning. First, manually close the leakage drain valve of the fire extinguishing device, then open the water supply valve to ensure sufficient water supply, start the fire valve, and close the manhole cover and door of the generator at the same time until the lower cover plate of the generator leaks. However, at present, the maintenance of water supply valve, drainage valve and fire damper is not in place, and it is found that the valves can not be used in use, resulting in the spread of fire.
3 Analysis of maintenance points of hydro-generator set
3. 1 Do a good job of equipment inspection.
Regular inspection and patrol inspection of equipment can ensure that problems can be found and solved in time, and ensure the normal and efficient operation of hydro-generator sets. During inspection and patrol inspection, attention should be paid to the following issues. 1) Record the operation parameters of the hydro-generator set, which must be within the specified range. If the operating parameters are found out of range, they should be recorded and checked in time. 2) Check and record the joint of primary circuit and secondary circuit, and confirm that there is no fever or discoloration at the joint, whether the current and voltage are normal and stable, whether there is abnormal sound, whether there is oil leakage at the oil circuit breaker, and whether the oil color and oil level are normal. 3) Is there any abnormal sound in the generator and is the steam turbine sound normal? If any abnormal sound is found, it should be checked and repaired immediately. 4) Check whether the generator has peculiar smell. If there is a burning smell, it means that the generator is not normal and should be checked and maintained. At the same time, it is also necessary to check and detect the swing and vibration of the generator to see if there is any vibration in the swing range of the viewer. 5) Check the hydro-generator set itself to see if the bearing temperature of the monitor is overheated. If there is local overheating, it is also abnormal. Daily inspection can be carried out with the back of your hand, and it doesn't feel hot. If necessary, it can also be tested with professional tools to ensure its normal temperature. 6) Check the brushes in all parts. Only a small amount of sparks are allowed in the brush part. If the value is out of range, it is abnormal and needs to be cleared.
3.2 Do a good job of daily cleaning.
According to the operation of hydro-generator set, do a good job of daily cleaning. Under normal circumstances, the equipment should be cleaned and inspected every day to ensure the normal operation and cleanliness of the equipment. When cleaning the equipment, pay attention to the dust and oil pollution of the equipment, so as to avoid damaging the equipment and affecting the normal operation of the equipment due to the dust and oil pollution, and timely clean up the hidden dangers that affect the operation of the equipment.
3.3 Do a good job in oil management
The oil consumption problem of hydro-generator sets is quite prominent, and good oil management is also a necessary condition for the normal operation of equipment. 1) Record the oil consumption of the equipment, and observe the oil consumption of the equipment in time to avoid mixing moisture and impurities in the process of oil consumption, reducing the purity of oil consumption and causing equipment damage. 2) Record the oil consumption of the equipment, and manage the special oil for the equipment to prevent the equipment from being used with it, and some even mix mechanical oil with insulating oil, causing serious damage to the equipment. To put an end to this situation, it is necessary to set up special managers to manage oil, mechanical oil and insulating oil should be managed in different categories to ensure proper oil use for equipment.
4 conclusion
The normal operation of hydro-generator sets has a great influence on the whole power station, which is related to the economic benefits of hydropower stations in China. Therefore, it is very important to manage and maintain the equipment, which is not only related to the long-term development of hydropower stations, but also related to the realization of socialism in China. Power stations should attach great importance to this, manage and maintain the equipment in combination with the actual situation, so that the hydro-generator set can better serve the hydropower station and the social modernization of the motherland.
[References]
[1] Ice Fai and Guo honge. Discussion on operation and maintenance of hydro-generator set [J]. Yunnan Hydropower, 20 13
[2] Liang Haibin. Operation and maintenance analysis of hydro-generator set [J]. Scientific and technological innovation and application, 20 13.
[3] Sun Xin, Dewey. On the necessity of strengthening the operation and maintenance of hydro-generator set in hydropower station [J]. Private Science and Technology, 20 12.
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