This paper mainly discusses the main factors affecting the insulation of the stator end joint of the hydro-generator set, and gives examples. The test weakening of the insulation of the stator winding end of the unit was carried out and the treatment method was proposed.
The civil-key word hydro-generator; stator end joint; insulation in the classification number 1312 than the identification code 8 i before the apricot in the hydro-generator stator insulation literature rarely mention the stator-end joint insulation, the main reason is the processing end The joint insulation is easier to break than the treatment bar, and the end joint insulation life is longer in the case where the manufacturing and maintenance processes are guaranteed. However, in the long-term operation of the generator set, due to the long-term effects of electro-mechanical and chemical factors, the electrical and mechanical strength of the stator-end joint insulation will gradually decrease, plus the manufacturer's manufacturing process or the stator winding field off-line process. The insulation of the stator winding end of the hydro-generator often becomes the weak point of the stator insulation of the generator. However, in the preventive test procedure of the helium equipment, there is no clear requirement to separately check the insulation of the stator winding end of the hydro-generator, so it is handed over. This is often overlooked in trials and preventive trials. This paper introduces the treatment of the accidents of the 3 units of Qingxi Hydropower Plant, and expounds the test and treatment methods of the main factors affecting the insulation of the stator winding end of the hydro-generator unit.
Type 2 end joint insulation type End joint insulation is divided into sleeve type insulation box type insulation and continuous insulation. The bushing type insulation is to insulate the inner portion of the winding of the winding first, and then to insulate the terminating portion. Continuous insulation is to fold the whole coil with a narrow mica tape. The advantage is that the effective part and the end part of the winding are really sturdy, and the tying is 4, and the squeegee is used to press the insulating varnish into the gap under constant pressure. This can increase the insulation level of the winding. Due to the large diameter of the hydro-generator unit, in order to facilitate transportation, the stator is often divided into 4 to 6 valves, which are assembled separately after the site. Some of the lower-line and end-joints are manufactured on site, due to the conditions on site. Restriction, usually the level and quality of the end joint connection is slightly worse than that produced in the factory. During operation, there are also small vibrations that are not synchronized between the lobes, which also affect the contact resistance of the end joints, which in turn affects the insulation level of the end joints.
3 The main factors affecting the insulation of the end joints as a whole, the small factors affecting the insulation of the end joints of the hydro-generator unit have the following aspects: 3.1 The contact resistance of the end joint is increased, and the contact current of the insulated water is lowered by the heat generated by the 弋 current. End connector. The connection method is related to the welding process. The welding methods currently used include lead-tin welding and silver-copper welding. The advantages of the lead-tin soldering method are lower soldering temperature and simple soldering process, but the lead-tin solder allows low current density and low tensile strength; while the silver-copper solder of the silver-copper soldering method allows high current density and resistance. The tensile strength is also high, but the silver-copper welding temperature is high and the welding process requirements are also high. Whether it is lead-tin soldering or silver-copper soldering, there may be a phenomenon that the soldering material is not tight inside. The degree of imperfection directly affects the magnitude of the contact resistance of the joint. If the head contact resistance increases by one, the degree increases. And then, the level of the edge is reduced, and the child of Yan Tong is caused by ginger. Therefore, improving the welding level of the production personnel and maintenance personnel is an important part of preventing joint insulation accidents.
In order to prevent the increase of the end joint resistance, we must measure the DC resistance of the winding every time the overhaul, and if necessary, measure the contact resistance of the end joint. According to the regulations, the DC resistance value of the winding is corrected for the error caused by the different lead lengths. After that, the difference between each other is compared with the measured value at the time of initial shipment or handover. If the difference is not greater than the minimum value, the cause should be ascertained. If the DC resistance of the winding increases, there is a possibility that the contact resistance of the terminal joint increases. Actually, the terminal joints in the case are changed under the action of electric heat and mechanical force, resulting in an increase in the contact resistance of the joint. 3 When the contact resistance of the joint increases and the current through the group is still rated current, the joint with increased contact resistance will locally heat up. Under long-term operation, the insulating material will gradually heat aging. Most of the signs of heat aging are that the insulating color gradually turns into burnt black, loses elasticity, becomes hard and brittle, cracks occur, and the mechanical strength is lowered. In severe cases, it is peeled off and dropped when subjected to vibration, thereby causing an accident.
3.2 The selection and preparation of the insulating material affects the insulation of the end joints, which is a serotonin. There are many kinds of insulating materials, which are divided into human hooks, organic and inorganic, and sometimes combined with different insulating materials, such as wire rod insulating mica tape insulating paint shrink band; end joint insulating and insulating box type insulating box ring Oxygen resin polyamide resin quartz powder. The insulation is made by the factory and is manufactured according to the size of the unit end joint. The insulation box and the joint should have a certain space. If the insulation box is too small, such as 4 units of Qingxi Hydropower Plant, when filling the insulating packing, many places of air bubbles Because the space is too small to come out, there is a large air gap or air bubble inside the insulation box, which seriously affects the insulation level of the unit. The insulating filler is mainly prepared by a ratio of epoxy resin polyamide resin quartz powder. The ratio is not determined according to the standard 4 of the polyamide resin. Too much quartz powder will cause the insulating filler to be too thick, and it is not easy to infuse, and after the infusion, many bubbles in the insulating box can not be produced, and the insulating filler is cured. Insufficient strength; too little polyamide resin will cause the insulating filler not to be easily cured; too much polyamide resin will cause the curing time of the insulating filler to be short, and the insulation becomes brittle and hard, and the elastic is not easily broken by vibration or impact. Of course, the preparation of the insulating filler is also closely related to the ambient temperature at that time. The above various ratios are imbalanced, which will cause poor insulation and directly affect the insulation quality of the end joint.
3.3 The manufacturing process of the end joint insulation Another factor that affects the insulation of the end joint is the process of making the end joint insulation. The lower end joint insulating and insulating box manufacturing process is to invert the insulating packing in the insulating box, and slowly put it on the joint, the process of inserting the joint can not be too fast, otherwise the insulating packing has not penetrated the insulating box. When the internal position is, the insulation box of the mountain will be left in the joint insulation, which will seriously affect the insulation performance.
The manufacture of the upper end joint insulation and insulation box is more complicated, firstly the bottom of the insulation box is sealed. There are two ways. The kind is made of epoxy mud, and the epoxy paste is solidified and then formed into an insulator. The part of the unit is insulated; the other is to use asbestos mud to lay the bottom of the joint, smash the insulation box, and inject insulation packing into the insulation box. After the insulation packing is solidified, the asbestos is removed. The advantage of the first method is that the epoxy mud sticks to the insulation of the wire rod and strengthens the insulation of the end joint; the joint insulation produced by the first method has a better appearance, and the insulation box mouth is relatively flat, and can be taken in the production of two methods. As for the filling of the insulating filler, there must be a step of notching. If it is not filled, it should be sweated 3 times in the case of incomplete curing, so as to prevent the bubbles in the insulating box from coming out completely and affecting the insulation level. In addition, after the Yuci Xiang injection, the bottom of the insulation box can also be made dense to prevent the leakage of the insulation filler from the bottom of the insulation box after being filled.
3.4 Mechanical vibration is known to the family. The stator end joints of the generator are all extended outside the core. The line is constantly affected by the external and its own mechanical and electromagnetic forces to generate vibration, especially for large generators, the electric level is higher than that of the joint extension core.
The impact is even greater. For example, the 2,3 units of Qingxi Hydropower Plant, in measuring the leakage current of the insulation box, found that the joint insulation box at the split lobe, especially across the two lobes, is more likely to break down or the leakage current is too large, which proves that there is not only The reason for the off-line process at the site is also the influence of the mechanical vibration of the insulation, the original of the fire. Therefore, the joint manufacturing process 1 at the splitting point should be particularly strict and careful, and should be checked as a key point during the test inspection.
Comprehensive 1 mentioned. Regardless of the factors, the insulation level of the end joint is an important part to prevent the insulation of the end joint.
4 Test method for detecting insulation and contact resistance of mustard end joints In the preventive test procedure for helium gas equipment, there is no clear requirement to separately check the insulation of the stator winding end joints of the hydroelectric generating set. In order to prevent accidents, according to the existing insulation of the unit. Weak points, such as the four units of Qingxi Hydropower Plant, draw on the test method of the insulation of the stator winding end of the turbine generator, and the following test method is more effective.
4.1 Leakage current measurement of the end joint insulation box The test method is to put the appropriate insulation filler on the bamboo before the windshield or rotor of the generator is lifted around the insulation box of the stator winding end. More will overflow, less 7 cobalt paper, in order to make tin afraid of paper close to the insulation box, tie the rubber box around the tin platinum paper to the micro-amp, short-circuit the stator winding winding with DC high-voltage generator The DC voltage is 13 掾, and the leakage current is read. If it is not added to 13.8, the discharge breakdown or the leakage current is relatively large, it is regarded as a defective insulation box and needs to be processed. The unqualified insulation box has a discharge voltage of 2, and the leakage current is between 3050, and the leakage current of the individual insulation box is very large; more than 1 due to the large number of stator winding insulation boxes, in order to speed up the test, the test can be first Insulating boxes are successively wrapped in tin-molybdenum paper for 2030, and then tried.
4.2 Measurement of Contact Resistance of End Connector Contact Resistance There are several methods for measuring contact resistance of large-capacity voltage drop and eddy current detection method by bridge-type infrared thermal image thermometer.
Infrared thermography thermometer measurement is a new method, which is to pass a large current in the stator winding, so that the stator joint produces a temperature rise. After a certain time, the temperature rise of the stator joint is stable. At this time, each camera is measured by an infrared camera. The temperature of the stator joint is compared to judge, and its advantage is that it is convenient and does not need to pierce the insulation of the joint to be tested. The bridge method is measured by the double-arm bridge. The induced eddy current is small, and the increase is not much. The loss is not fire. At this time, the total current is only increased to the song, and the change of the phase angle 3 is not large. On the contrary, if the joint structure is firm, the contact is good, and the weld is filled, the resistance of the run-through through the road company will increase greatly, and the total current will increase accordingly, hehe, The phase angle 3 change is also better, from 3 to æµ¼. Therefore, the root and the size of 3 can judge the welding quality of the joint. This method is only suitable for the joint measurement with the integral joint structure. The biggest advantage of this method is that the square ten bridge method and the large current drop method need to be damaged. The joint is insulated, and the high current jade drop method is more accurate and sensitive than the bridge method. Therefore, in this case, the bridge method is not used, but the high current voltage drop method is used. The high current voltage drop method is a current that is passed through the windings without being dried, and the joint is measured. The resulting pressure drop is calculated according to =67. The method is to determine the contact resistance of the joint after the end joint has been welded. It also has a certain dispersion. The good end contact resistance is only a few micro ohms, and the contact resistance of most solder joints is small. The turbulence resistance of the length 1 conductor is small. Bad end connector values, and many times greater than the contact resistance of a good connector. The eddy current detection method is based on the fact that the stationary monolithic conductor induces the eddy current in the alternating magnetic field. If the joint structure is not strict, it does not need to pierce the insulation of the joint to be tested, but the probe is used for measurement. The radio test results are more dispersive. So, nowadays it is not measured by this method.
The above four measurement methods are measured by the large current voltage drop method when the joint is not insulated, and the joint package is insulated and then gradually measured by an infrared camera.
Court 21 eddy current detection method å’• 1. good joint 2. bad joint 3. probe no load 5 accident example 5.1 accident overview June 12, 1997, Qingxi hydropower plant 3 generator set stator winding suddenly short-circuit, protection action. After the inspection, the insulation resistance of the phase stator windings was found to be 岑. Demolition of the motor stator outlet direction cover and windshield, found that there are many stator winding end joint insulation box fragments on the dice along the rotor magnetic pole to climb into the apricot, and found that the 定å+, the stator winding upper end joint insulation box lamp Three pieces have been broken, and the upper end of the stator in this direction has been blackened to short-circuit the stator winding phase.
5.2 The reason is that the rated power is 423,531, the rated voltage is 13.8, the rated current is 1772, the amount of the frequency is 50, the rated power factor is 85, the stator winding is connected, the number of phases is 3, the insulation grade is grade After the insulation box, the 2,3 unit overhaul in the stator winding end joint insulation box group + parent, parent, +, direction of the field off-line split joint, indicating that the foot should be enough to dry the stator winding on-line Leisure, followed by the manufacturing process of the manufacturer, as well as the place where the mechanical vibration is running. The reason why the insulation box of the fixed joint is the weak point of the insulation is mainly caused by the insulation box being too small and the original flash of the insulation filling process, so that the insulation material in the insulation box is heavily filled and unfilled to form insulation. There is a gap in the light inside the box, there is only a little insulation filler in the insulation box, and most of the insulation box is the gap 3; the lamp of the upper end of the insulation box is wound around the beam, and the insulation is in the field line. After the box is erected, it can be nested. After the insertion, the insulating box that is cut open is replaced by the gap of the lamp. The upper end of the insulating box itself is not covered tightly, and there is no insulating material. 4 The gap between the upper covers is tight, especially at the four corners of the gap, and it is easy to become the four corners of the insulating weak point 3.
Based on the above situation, when there is a slight overcurrent between adjacent insulating boxes during operation, these weak points of insulation may directly break through the insulating box or creep along the gap to cause phase-to-phase short circuit. In the fire repair of these three units, the observation of the length inspection of the insulation box confirmed this.
5.3 Treatment plan In the handling of accident handling and other three unit end joint insulation boxes, according to the test knot, the unqualified insulation box is knocked off with a woodworking chisel. This process requires a note 1 to use a rag pad before hitting the insulation box. The wire rod of the insulation box is good, so that the protection bar 2 should not damage the wire rod insulation; do not damage the wire rod joint. When the insulation box is knocked out and cleaned, the wire rod joints can be deformed. Therefore, the special tool is used to correct the wire rod joint and the contact resistance measurement is performed. For the individual joint cracking or the contact resistance is unqualified, it should be re-applied. Advance welding and correction. Then replace it with a new insulation box and adjust it to make up the seam with insulating material.
For the lower end of the winding insulation box does not open this order, you can directly use the insulation box to install the insulation filler into the lower end of the wire rod joint and adjust the fixing, and then the fixing plate can be removed after the insulation filler is slightly cured. However, for the upper end of the winding insulation box, after the insulation box is inserted into the wire rod joint, first use 2, thick epoxy resin board and epoxy resin mixed with polyamide resin as adhesive, seal the bottom of the insulation box and the big mouth Large gap between the bars. Some need to cut two and a half inches of insulation box that can be fed into the wire rod joint, and also use epoxy resin and polyamide resin to make the adhesive to stick the joint between the two halves, leaving no gap, etc. After the amide resin mixed adhesive is cured, the insulating box is adjusted, and then the gap between the large opening of the bottom of the insulating box and the wire rod is sealed with epoxy mud, and the insulating filler is poured after the epoxy mud is solidified. Generally, the filling is performed in three times. For the first time, each insulating box is filled with about 810 thick. It is not leaked and waits for it to be slightly solidified before filling the insulating box for the first time and the first time. The filling speed should not be too fast. . Wait for the bubbles in the box to drain slowly.
Every time before the overhaul of the insulation box, it should be tested several times to adjust the formula of the insulating filler to select the ideal formula.
Fill the full and slightly raised with epoxy mud to replace the insulating box cover, pay attention to the gap should not be left, the corner has a slight arc transition, for the lower end of the insulation box is filled with epoxy mud into a transitional arc to the root of the bar . Treatment is carried out for testing. According to the DC leakage test force method of the end joint insulation, try to insulate each insulated box. In order to check whether the whole set of windings is damaged during the processing of the insulating box, it may be regarded as the situation on the site. The stator windings of each phase are subjected to 2.0 times or 2.5 times of DC withstand voltage and 1.5 times of AC withstand voltage test. After all the tests are passed, the generator insulating paint is sprayed.
6 Conclusion Based on the above analysis and the accident situation of Qingxi Hydropower Plant, the insulation of the hydro-generator 纟1 end joint is an important part of the whole insulation of the generator set. There are many factors affecting the insulation of the end joint. The ambient temperature is about the time of the production or treatment end test. 2028, part of the upper end of the insulating material epoxy resin ring of the epoxy resin 3; 412 ring polyamide resin 3; 414 2; amide resin 341 fat polyamide resin 65121 added a little anhydrous alcohol stirring 1 The amount of water can be too much to be added to the insulation box.
After mixing evenly, it can be poured into the insulation box and then inserted into the lower end joint.
黯1 is suitable for the amount of quartz. When the insulating filler in the insulating box is filled and cured after about a few days, it can be repaired. For the epoxy joints for the upper end insulation box, it should be carried out in strict accordance with the specifications according to the end joint processing steps, and the quality of the treatment is a key factor affecting the insulation of the end joint. At the same time, it is necessary to strengthen the training of the skills of the end joints, and continuously raise the joints. The date of receipt is 200102. The introduction of Chen Wentian 1970. In July 1992, he graduated from Guangdong University of Technology, majoring in power system automation, and is now in the water power maintenance of Guangdong Electric Power Group Corporation. The center is engaged in electrical maintenance work, electrical assistant engineer.
Soil Connections Page 24 5.5 Laminations in the installation room or in the pit Due to long-distance transportation and hoisting, the core of the large hydro-generator is easily deformed. If it can be laminated in the pit of the hydropower station, it will not be hoisted or less hoisted after stacking, and the quality will be more guaranteed.
I motor 1 Cheng Yushu editorial board. Motor Process Manual, Section 9 Synchronous Motors 1. Beijing Machinery Industry Press, 1979.
Into the motor manufacturing technology. Beijing Machinery Industry Publishing Received 310321 Yesterday's Profile Zhou Hua Leng 1938, graduated from the Department of Electrical and Power Engineering of Tianjin University in 963. He is currently engaged in motor teaching and research, professor.
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