Hebei Province Electric Power Company, Shijiazhuang, Hebei 050021, China; 2. Hebei Electric Power Research Institute Group accident brief. Analyzed and studied how to improve the current detection methods used in major repairs and to ensure timely detection of stator winding winding defects. Several suggestions were made for maintenance work. In recent years, large-scale turbine generators are often without any precursors. The occurrence of accidents under the circumstances reflects the current limitations of conventional test items and test cycles. Some of the information on accidents cannot be captured in time. Therefore, it is absolutely necessary to research and pay for the effective and timely testing of the shirts.
1 Accident example A power plant with a 100 turbine generator overhauled and connected to the network for only 4 months had a short-circuit accident due to starting windings. Before the occurrence of this accident, the machine was rated for normal operation with a nominal active load, reactive power 40 voltage 220, and rotor. Current 1230 people. In the event of an accident, the stator of the generator's longitudinal differential generator is grounded, and the protection of the generator is negative sequence overcurrent, and the generator and system are disconnected. The generator side cover collapses. Hungry insulation and smoke. In the cold water, the spurs of the side of the excitor's side of the yoke gradually increased from the end of the hunger-sweating line to the end of the tie. A short circuit to the ground arc between the lead of the Yamaguchi mouth. Two wires were blown and the insulation of the adjacent wire rods was burned by the arc. There is a flashover mark on the end cover of the bar, and the bar and the water joint are insulated and burned.
Hebei Shijiasheng 0,50,021 more. The analysis considers that the turbine generator is an early product. Due to the influence of factors such as the operating conditions of the insulating material used in the manufacturing process quality, there are insulation weaknesses such as stator end winding joints and hand-bag insulated lead connectors. In addition, the generator is designed with a sturdily load, and the hill frequently participates in peak shaving in recent days, so that the differential expansion of the stator core and the winding causes an alternating stress in the stator end support system, resulting in the end of the stator winding. Structural vibration, not to mention wear and corrosion corrosion, the stator winding end support structure stator groove wear and stator end, 3 parts harmful deformation, coupled with welding head welding quality is not good The fatigue strength of the welding place is lower than the copper wire fatigue strength, so Tiny cracks occur at the solder joints. Smaller leakage points appear. It is difficult to find the insulation after the package is insulated. As the insulation around the leaking point is soaked, the stator windings are partially discharged due to moisture, and the partial discharges quickly lead to insulation aging. And damage, resulting in a short phase between adjacent bars above and below, under the action of the water vapor and metal ions, resulting in the end of the tank at the end of the hydroelectric joint discharge to the ground, 2 stator winding insulation detection of cold vapor Stator stator phase-to-phase short-circuit accident occurred on the generator wheel, North China Electric Power Research Institute and Harbin Daji Research Institute developed the stator winding end of the generator. Packet insulation state measurement method and corresponding standards, the measurement method is the winding end portion and the surface potential measurement end of the insulating leakage current method. In order to determine that the insulation condition of the stator end of the 100-Jin-Jia water double-cooled air-cooled inner cooling unit is good enough, the measuring method of the winding end-potential of the production end is tested repeatedly, but the mining is not very satisfied with the mountain, and the insulation of the end hand-rail is usually not good or bad. Affecting the safe operation of the double-water internal-cooled generator is discussed in the discussion of the electric power plant's preventive tests. The amendments to the existing regulations have not been recorded on the application of the method in the dual-water internal-cooled generator. Therefore, the method is used to detect 100 river-level generators. In the case of insulation, it is still judged by the traditional needle stick method, that is, using a special probe to penetrate through the outermost layer of the stator winding winding bag insulation, and then use the 2500 shake test bar to ground insulation resistance. There have been many hidden accidents discovered through the stitching method, which has played a positive role in ensuring the safe operation of the unit, but the stitching method has damaged the insulation of the stator end windings to varying degrees; anatomical examination of the blown leads revealed that the wire rods Insulation is severely stratified, and the insulation material used has been embrittled. The copper surface of the copper rod is relatively accidental when it is used to find micro-leakage defects.
2.1 Stator winding winding insulation test content According to the requirements of the Ministry of Electrical Equipment Prevention Test Procedures, the generator stator winding shall be subjected to DC and AC withstand voltage tests during overhaul. The AC power frequency voltage withstand test mainly focuses on finding the insulation defects at the stator winding slot and slot, while the DC withstand voltage test focuses on finding the defects of the end winding. In the DC voltage withstand test, there is no capacitance current in the end insulation, so the end windings at a certain distance from the notch still retain a higher electric card, but the joint farther from the iron core is due to the end winding. The role of surface insulation resistance, insulation applied to the insulation in the end of the insulation needs to effectively improve the progress of the seven people, the normal operation of the stator end of the main contributing Zhuanshan winding stretch resistance distribution of resistance by the high resistance area The low pressure in the zone is divided by the value, and the voltage at the insulation end of the winding at the end of the household winding is very low. When the winding is relatively clean and the end bar is at a distance of 3 from the notch, its operating pressure has decreased to about 2,1. Obviously, this odor is insufficient to have a defective insulating mountain, so the insulation of the end handbag is basically 7. The dielectric strength requirements of the author in Germany Siemens 1 sector. When the port factory inspected the power generators of Hanfeng Power Plant, it learned that the 660 River Turbine Generators manufactured by them did not cover insulation of the hydropower joints, and the Jinqu junction was bare in the air, ie, as long as the phase insulation was good, no accident would occur. The weak link between the phase insulation is the insulating rope at the end of the tie. In normal operation, the surface resistance of the bar stretch and the insulated wire at the end have sufficient insulation for the deer but when the temperature inside the generator is high, even when the water leaks, the insulation of those ends that are fully insulated under normal conditions It will also be damaged by the insulation of the package that destroys its compactness. The insulation of the hand bag will be slowly wetted by the micro-osmotic water, and it will be heavily damped, thus causing a short circuit at the end of the stator. Although cutting the end of the phase between the insulation of the rope due to the insulation strength of the insulation after the rope is very poor can slow down the end of the insulation accident, but it is impossible to prevent accidents. Therefore, the test of the insulation condition at the end of the generator is mainly to check the micro-leakage of water at the end of the stator instead of checking the electrical strength of the hand-bag insulation, of course. The microleakage phenomenon can be determined initially by measuring the electrical strength of the insulation.
2.2 The main parts of the stator winding leakage and reasons to prevent the insulation breakdown of the generator end of the accident, the aspects of the machine to avoid excessive humidity, in particular, to prevent dew condensation on the stator bar surface can be through dehumidification and to ensure that the stator temperature must be high At the two ends of the inlet temperature to prevent it; the other is to prevent leakage of water leakage at the end of the joint, which is now the leaking water at the sealing joint of the marking rod and the water joint; the upper and lower bar of the stator and the welding seam of the head cap welding; stator pressure The cooling water pipe of the ring leads to the leakage of the water joint at the outlet; the plastic pipe of the stator is long, colliding with the end cap or the plastic pipe, especially between the phases.
The cause of leaking faults is due to poor welding of the end of the bar, causing water leakage. Larger leak points can be found in the hydrostatic test, while smaller leaks such as welding blisters may not be created in the hydrostatic test. Wear it; Class 1 圮 end vibration and other factors caused by fatigue cracks in the water pipeline and leaking wood such accidents are likely to occur at the end of the welding point or insulated water pipe nut connection point, and the rapid development rate, easy to cause insulation breakdown ACCIDENT.
2.3 Dense test to detect leaking faults at the end of the microleakage stator. Multiple failures were found in hydrostatic tests of major overhauls. However, the leak points found at this time were more severe. The early microscopic water seepage point was due to the insulation of the bread plant. 4, water leech test stand found.
The use of DC voltage withstand test and needle stick method to test the insulation status of the hand bag has its limitations. In order to be able to find out the micro leakage, the stator water circuit airtight test can be performed. At present, most foreign countries have adopted the airtight test method for the sealing of the water-cooled windings of turbine generators. It can make full use of the accuracy of gas leak detection to check the leakage point. Mountain plant gas is more accurate.
First of all, to ensure that there is no residual beam inside the generator winding. If there is any remaining water, it must be filtered and dried with filtered dry compressed air or nitrogen. Allow to dry the compressed air or nitrogen to 0.35, 3 leak detection pressure. During the airtight test, it is not allowed to compensate the internal gas of the generator winding when the pressure reaches 0.3. The gas at the side of the turbine and the re-inflation pressure is 0.05%, and the 2 flon gas will continue to be charged with compressed air or nitrogen. When testing its sealing performance, the butane lamp first goes into the coarse inspection. That is, a small amount of gas is emitted from the excitation and the top-end exhaust valve, where the butane lamp detects whether air or nitrogen is filled with sufficient amount of F12 and has completely diffused the butane gas to burn in the air to appear blue. The combustion in 12 is green, so as to ensure that the joints at the ends of the leak detection windings are slowly moved outside the transition leads of the insulated water intake manifold, the outlet bushings, etc., and only the leaks are detected one by one.
After the start of recording, every 1 recording has been made. After 12 hours, the leakage pressure drop of 24 is calculated. If the leakage rate of 24 is less than 0.2 starting test pressure, it is proved that the winding has no leakage point.
At the same time, attention should be paid to setting as many temperature measurement points as possible during leak detection. The environmental temperature difference between the end of the test and the start of the test should be as small as possible.
Maintenance is the simplest.
3.2 Use of simplified bypass If simplified bypass is adopted, desuperheating water shall be introduced and a valve for desuperheating and pressure reduction shall be used to discharge the soda into the condenser. Therefore, a desuperheating energy dissipation device shall be installed on the condenser. 6 condensate enthalpy and circulating water pump must be activated. If the vacuum is low, it cannot be discharged into the condenser and it needs to be emptied. Especially during the temperature rise of the 2nd furnace, the turbine has a constant load, which easily affects the vacuum. If you want to simplify the bypass alone, you don't plan to use the desuperheater to set the parameters. The capacity of the simplified bypass should be set according to the 1530 of the furnace evaporation. This can satisfy the cold and warm state start without opening the furnace superheater emptying door. If you want to meet the unit nine state 1!
Dynamic and bypass capacity shall reach 50 °C of furnace evaporation, and air exhaust valves shall be opened to increase the main steam temperature. Bypass valves shall be installed at the lowest position on the side of the turbine and should be as close as possible to the main valves in order to facilitate the improvement of the master. Steam temperature in front of the valve. According to the relevant data, the bypass capacity of the 200-th river unit in Qingshan Power Plant is 15, and the bypass capacity is relatively small in the operating condition. When the cold state is started, the temperature difference between the boiler side and the turbine side is large, and the superheater is sometimes discharged to the air. The door opens to raise main steam temperature.
3.3 The temperature of defrosting pipe plus decompression and decompression machine is more than one desuperheater and pressure reducer, and then the temperature of the main steam is increased by the desuperheating pressure reducer to the required value. This kind of tender reduction; frequently. As the main steam flow pressure and temperature increase when the furnace is ignited, the opening of the temperature reducing and decompressing adjusting door needs to be constantly changed, which has a higher requirement on the quality and control of the valve. Judging from the current situation of each power plant, frequent start-up is easy to damage the temperature reducing regulator, and the main steam flow is too bad to adjust. If this scheme is adopted, it should be put in when main steam temperature and main steam flow are relatively high, and high-quality inlet valves should be selected.
4 Scheme Analysis 3.2 Scheme If the system is simple, the bypass will be set on the main pipe in front of the main valve, only the first furnace can be used for simple bypass when it starts, and because the steam can reach the pressure and temperature, it can save. The funds are far less than the sub-investments, and the maintenance and repairs increase = if the 3.1 plan and the 3.3 plan are added. That is, the condensing pipe is used to start the machine in the cold and warm state, while the second furnace uses the desuperheater and pressure reducer to increase the parameters of the rush steam to reach the smelting furnace condition. Each start can save a lot of heat and work, is a relatively complete program.
5 settings of temperature reducing regulator 5.1 capacity test set up to talk. The steady-state combustion of the boiler shall be sufficient to ensure that the load on the fluidized bed furnace does not guarantee that the furnace superheater does not dry and the minimum cooling flow is 15.
The soil satisfies the second furnace to increase the main steam parameters to reach the furnace conditions, and the adjustable capacity is at least 12, of course, smaller.
6. There must be an excellent pre-heating system that is in hot standby at any time to avoid leaks or motions that prevent the device from being put back into use. The Sulzer doors are of relatively good quality after actual investigation. Based on the above original flash desuperheater and reducer, at least 12024 should be satisfied, and the Fanbei 5.2 control settings. When the turbine is dumped under condensing conditions or under less industrial extraction conditions, the desuperheater and pressure reducer will not start. At this time, the furnace safety door exhausts, the furnace opens and drains the door, and the related hydrophobicity is opened. The grid will soon be loaded, and if there is a fault, shutdown will stop.
1. When the steam turbine is equipped with an industrial extraction volume of 12,0 and above, the load dumper starts the desuperheater and pressure reducer. It is mainly controlled by unit load of 0 and industrial extraction volume of 1202.
6 concludes the comprehensive analysis thinks to set 5 above the debridement branch 10 15 of the defrosting mother tube and 2401! The desuperheater and pressure reducer is a more suitable solution to enhance the main steam parameters of the 1401 double pumping unit; it was received on 1999 and continued on page 14. 3 Suggestions The test of the insulation condition of the generator end is mainly to check the micro connections of the stator end water joints. Leakage, therefore should strengthen the welding quality of hydropower joints suggest that all units including water hydrogen hydrogen cooling generators actively apply airtight detection to check the tightness of the water joints.
When designing and manufacturing a turbine generator, a manufacturer may consider that its stator hydropower connector does not cover external insulation to expose its metal connections.
Because the phase voltage is relatively low, the stator windings are properly partitioned, and insulation plates are added on both sides of the stator windings of the subarea to make the insulation plate leak out of the stator windings of the hydroelectricity. + Less is caused by poor quality of corpse manufacture. The factors affecting the quality of welding are the cleanliness of brazing metal surfaces and the control of welding temperature, the operation skills of shank welding and the quality of traitors. Therefore, manufacturers should strengthen management and avoid similar defects.
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