Zheng Xiaojiang, Song Songsen, Wan Li 21. Hebei Electric Power Company, Shijiazhuang 050021, China; 2. Brief report on the accident of Hebei Electric Power Research Institute. Analyzed and studied how to improve the detection methods adopted during the current overhaul and the methods to ensure the timely detection of the stator end winding defects, and put forward some suggestions for the maintenance work. In recent years, large steam turbine generators often have no precursors. Accidents in the case reflect the limitations of the current routine test items and test cycles, and some of the accident precursor information cannot be captured in time. Therefore, research and payment of effective and timely testing methods are very necessary.
1In the case of an accident, a 100-turbine generator of a power plant was overhauled and connected to the grid for only 4 months. The short-circuit accident of the winding was delayed. The machine was rated for normal operation before the occurrence of the rated active load, reactive power 40 voltage 220, rotor The current is 1230 people. When the accident occurs, the generator longitudinal stator generator grounding, 4 generator negative sequence overcurrent protection and other protection actions, the generator and the system are unpacked. The generator side cover is collapsed. Insulting the fire from the hunger. The cold water in the interior is constantly elbowed, and the end of the stator side of the excitation side is wound around the end of the hungry sweat line. The phase-to-mountain leads are short-circuited to the ground. The two bars are blown, and the insulation of the adjacent slot bar is arc burned. The wire rod has a flashing mark on the end cover, and the insulation of the wire rod water and electricity joint is burned.
Hebei Shijiasheng more than 0,050,021 pounds. The analysis considers that the steam turbine generator is an early product. Due to the influence of the operating conditions of the insulating material used in the manufacturing process quality, there are insulation weak links such as the stator end winding joint hand bag insulated lead joint. In addition, the generator design has a load-carrying load, and the mountain frequently participates in peak shaving in the near future, causing the difference in expansion between the stator core and the winding to cause alternating stress in the stator end support system, thereby causing the end of the winding of the household. Structural vibration, due to insulation wear corrosion, stator winding end support structure stator groove wear and stator end, 3 parts harmful deformation, plus welding head welding quality is not good, the fatigue strength of the weld is lower than the fatigue strength of the copper wire, so Small cracks are generated at the welded joints, and small water leakage points appear. It is difficult to find after the insulation is covered. As the water leakage around the water leakage point is large, the stator windings are partially discharged due to moisture, and partial discharge quickly leads to insulation aging. And the damage, causing the wire rods adjacent to the upper and lower sides to be short-phased, under the action of water vapor and metal ions, causing the end cap of the water-electric joint at the end of the trough to discharge, and the cold air of the stator winding insulation of the stator The end-to-phase short-circuit accident at the stator end of the wheel generator, the North China Electric Power Research Institute and the Harbin Daji Institute of Research and Development have developed the stator winding end of the generator In order to determine the insulation condition of the stator end pack of the 100 Hejia double water internal cooling unit, the end winding surface potential measurement method is repeatedly tested, but the knot mining is not very satisfactory, and the end handcuff insulation is usually not good or bad. Influencing the safe operation of dual-water internal cooling generators In discussing the preventive tests for electric power installations, I have revised the old ones to remember whether the method is popularized and applied on the dual-water internal cooling generators. In the case of insulation, it is still judged by the traditional pinning method, that is, the outermost layer of the stator end winding insulation is pierced with a special probe, and then the insulation resistance of the test bar is grounded by 2500. Using the needle-punching method, it has been found that there are too many hidden dangers in the accident, which plays an active role in ensuring the safe operation of the unit. However, the needle-punching method damages the insulation of the stator end winding to varying degrees; the anatomical inspection of the burned lead shows that the rod is The insulation is severely stratified, and the insulating material used is already embrittled. The copper rod surface is copper and there is a large contingency when looking for micro water leakage defects.
2.1 The contents of the stator end winding insulation test shall be in accordance with the requirements of the Ministry of Electrical Equipment Preventive Test Procedures, and the DC and AC withstand voltage tests shall be performed on the generator stator windings during overhaul. The AC power frequency withstand voltage test mainly focuses on the insulation defects at the slot and slot of the stator winding, while the DC withstand voltage test focuses on the defects of the end winding. In the DC withstand voltage test, since there is no capacitive current in the end insulation, the end windings at a fixed distance from the slot still retain a higher electric card, but the joint farther from the core, due to the end winding The effect of the surface insulation resistance, the effective application of the insulation to the end windings of the insulation is in urgent need of progress. The normal operation of the stator end is mainly due to the resistance of the surface winding of the mountain winding extension. The low-lying area is divided according to the value, and the mountain is connected to the grounding point of the insulation of the 1st package at the end of the winding of the household. Therefore, the voltage level at this place is very low. When the winding is relatively clean, the end bar is at a distance from the slot 3, and its running pressure has been reduced to about 2,1. Obviously, this electric taste is not enough to be defective in the insulated mountain, so the end of the hand bag is basically insulated. The insulation strength requirements of the author in the German Siemens 1 world. When the port factory inspected the generators of the Fengfeng Power Plant, it was learned that the 660 River Turbine Generators produced by the 660 River Turbine Generator did not contain insulation, and the gold flex joints were exposed to the air, that is, as long as the phase insulation is good, there will be no accident. The weak point of phase insulation is the insulated rope that binds the end. In normal operation, the surface resistance of the bar extension and the insulated rope at the end have sufficient insulation for the strong deer. However, when the temperature inside the generator is very high, even when the water leaks, those end insulations that are completely qualified under normal conditions are insulated. It will also be damaged by the damage of the bag that is less dense than the bar. The insulation of the handbag will be slowly wetted by the tiny water seepage, causing severe moisture, which will cause a short circuit accident at the end of the stator. Although the end-to-phase insulation tie ropes at the end of the cut can weaken the end insulation accident due to the poor insulation strength of the insulated tie rope after damp, it is impossible to prevent the accident from happening. Therefore, the test of the insulation condition of the generator end is mainly to check the micro-leakage of the water joint at the end of the stator, instead of checking the electrical strength of the insulation of the handbag, of course. The micro-leakage phenomenon can be initially determined by measuring the small amount of insulation electrical strength.
2.2 Main parts and causes of leakage of stator windings To prevent insulation breakdown accidents at the end of generators, it is necessary to avoid excessive humidity in the machine, especially to prevent dew condensation on the stator bars and to ensure dehumidification and high temperature in the stator. In addition, it is necessary to prevent the leakage of water at the ends of the joints. The water pipe of the ring is leaking to the water joint of the outlet; the plastic pipe of the stator is long, colliding with the end cover, or the plastic pipe is in contact with each other.
The cause of the water leakage failure is due to poor welding at the end of the wire rod, causing water leakage. Large leaks can be found in the water pressure test, and some small water leakage points such as welding sand holes are not increased from the water leakage test in the water pressure test. Wearing the reason; the type 1 圮 end vibration and other factors cause the water pipe fatigue crack and the leakage of wood is easy to occur at the end welding point or the insulating water pipe nut connection point, and the development speed is fast, easy to cause insulation breakdown ACCIDENT.
2.3 dense test to detect the leakage of water at the end of the micro-leakage stator is a multi-fault failure. Most of the faults have been found in the overhauled hydraulic test. However, the leak point found at this time has been more serious. The early micro-leakage point is due to the external insulation factory. 4, the leeches test booth found.
The DC voltage withstand test and the needle-punching method have their limitations in testing the insulation condition of the hand bag. In order to find the micro-leakage, the stator water circuit air-tight test can be performed. At present, most foreign countries have adopted the airtight test method for the inspection of the water-cooling windings of steam turbine generators, which can fully utilize the accuracy of gas leak detection to check the leak points. The mountain plant gas is more accurate.
First of all, it is necessary to ensure that there is no residual beam inside the generator winding. If there is residual water, it must be cleaned by filtered dry compressed air or nitrogen and dried for inspection. Allow 1 dry compression or nitrogen to 0.35 river, 3 leak detection pressure During the airtight test, no gas is allowed to be supplied to the inside of the generator winding when the pressure reaches 0.3. The 2 fluorocarbon gas with a pressure of 0.05 PCT at the side of the turbine is continuously filled with compressed air or nitrogen. When testing its sealing performance, first use a butane lamp for coarse inspection. That is, a small amount of gas is released at the excitation and the top exhaust valve, and a butane lamp is used to detect whether the air or nitrogen is filled with a sufficient amount of F12 and all of the diffused butane gas is burned in the air to appear blue, and The combustion in 12 is green, to ensure that the transition lead of the insulated water conduit confluence pipe at the joints of the leak detection winding ends and the outlet casing are slowly moved outside, and the leakage is detected one by one.
After the start of recording, every 1 record, after 12, calculate the leakage pressure drop of 24, if the air leakage rate of 24 is less than 0.2 initial test pressure, it proves that the winding has no leakage point.
At the same time, it should be noted that as far as possible, the temperature measurement point should be set at the time of leak detection, and the temperature difference between the end of the test and the beginning of the test should be as small as possible.
Maintenance is the simplest one.
3.2 Simplified bypass If simple bypass is adopted, it is necessary to introduce desuperheating water and use the desuperheating and decompression valve to discharge the steam into the condenser. Therefore, the desuperheating and energy dissipating device should be installed on the condenser. It is necessary to condense the water enthalpy and the circulating water pump. If the vacuum is low, it cannot be discharged into the condenser and needs to be emptied. Especially in the ignition process of the second furnace, the steam turbine has a constant load, which easily affects the vacuum. If you want to simplify the bypass only, you are not going to use the desuperheater to pick up the parameters. The simplified bypass capacity should be set at 15 30 of the furnace evaporation, which can be used to initiate cold and warm start without opening the furnace superheater drain. If you want to meet the unit's extreme nine state 1!
The bypass capacity should reach 50% of the furnace evaporation. The open steam valve can be opened to increase the main steam temperature. The bypass valve should be set at the lowest point of the turbine side pipe and should be as close as possible to the main valve to facilitate the main The steam temperature in front of the valve. The relevant information is that the bypass capacity of the 200 River boundary unit of Qingshan Power Plant is 15. The running condition is that the bypass capacity is too small. When the cold start is started, the temperature difference between the boiler side and the turbine side is very large, and sometimes the superheater needs to be exhausted to the air. The door opens to increase the main steam temperature.
3.3 Condensation pipe plus temperature and pressure reducer machine 1 set of desuperheater and pressure reducer, and then increase the main steam temperature to the required value through the desuperheater and pressure reducer, this kind of tender reduction; minus 110, 1 scoop start relatively frequently. Since the main steam flow pressure and temperature are continuously increased during the ignition of the furnace, the opening degree of the temperature reduction and pressure reduction adjustment door needs to be constantly changed, which requires high quality and control of the valve. From the current situation of the use of power plants, frequent start-ups are easy to damage the temperature and pressure reducer, and the main steam flow is too small to adjust. If this scheme is adopted, it should be input when the main steam pressure and the main steam flow are relatively high, and a high-quality inlet valve should be selected.
4 scheme analysis 3.2 scheme If the system is simple to set the bypass on the main pipe in front of the main steam valve, only the first furnace can be started with simple bypass, and when the steam reaches a certain pressure and temperature, it can be invested. The funds are much less than the secondary investment, and the maintenance and repair volume increases = if the 3.1 and 3.3 programs are added. That is, the condensate pipe is used in the cold state of the machine, and the second furnace uses the temperature reducer to raise the parameters of the busy steam to reach the furnace condition. Each time it starts, it can save a lot of heat and working fluid, which is a relatively perfect solution.
5 settings of the desuperheater and pressure reducer. The stable combustion of the boiler should be satisfied. For the fluidized bed furnace load, the minimum cooling flow rate of the furnace superheater is not guaranteed, that is, the furnace load is 15.
The soil meets the requirements of the second furnace to raise the main steam parameters to reach the furnace condition, and the adjustable capacity is at least 12, of course, it will be better if it is smaller.
6. There must be an excellent pre-heating system, and it is always in a hot standby to avoid leakage or 1 motion, so that the device can not be put into standby. After actual investigation, the quality of Sulzer Gate is relatively good. Based on the above original flash desuperheater, it should meet at least 12024, é—± 5.2 control settings. When the steam turbine is under load in the steaming condition or less industrial steaming conditions, the temperature reducing and pressure reducing device will not start. At this time, the furnace safety door will exhaust the steam, and the furnace will open the empty door to open the relevant water. If possible, the unit will It will soon be connected to the grid with load, and if there is a fault, it will stop and shut down.
1. When the turbine is equipped with industrial steam extraction capacity of 12,0 and above, the unit will start the temperature reduction and pressure reducer after the load shedding. It is mainly controlled by a unit load of 0 and an industrial steam extraction amount of 1202.
6 Conclusion Comprehensive analysis considers the setting of 5 or more condensate branch 10 15 condensate mother tube and 2401! The desuperheater and pressure reducer is a suitable scheme for upgrading the main steam parameters of the 1401 double pumping unit; the date of receipt is 1999, which is connected to page 14 and 3 points. It is recommended to test the insulation condition of the generator end mainly to check the micro joint of the stator end. Leakage, therefore should be strengthened on the quality of welding of hydro-electric joints. It is recommended that all units including water-hydrogen-hydrogen-cooled generators actively apply airtight detection to check the tightness of mustard joints.
When designing and manufacturing a turbo generator, the manufacturer may consider that the stator hydroelectric joint does not include external insulation to expose the metal joint.
Due to the lower phase voltage, the stator windings are properly partitioned, and an insulating plate is added on both sides of the stator windings of the partition, and the insulating plate is discharged from the stator windings. + Less is caused by poor quality of the corpse, and the factors affecting the quality of the welding are the control of the cleanliness of the brazed metal surface and the control of the welding temperature, the operation skill of the mountain and the quality of the agent. Therefore, manufacturers should strengthen management to avoid similar defects.
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