In addition to understanding the structure of the car when disassembling a car, I personally think that special attention should be paid to the design philosophy of the original car designer. The poster should know what is the biggest difference between European cars and Japanese cars. I don't know what type of car the poster is dismantling. Note: 1. The overall structure, you can finally see its important cross sections. 2. The inner and outer panels are connected by bolts. Some German cars are connected with bolts, while Japanese cars are almost always hemmed. The author can pay attention to how they are structured and their advantages. 3. The arrangement of sheet metal elements, such as where there are many sheet metal elements, indicating that the strength is insufficient, etc., this information can be collected,
Method of testingt Generator Stator End Handbag Insulation < /p>
1? Foreword
200 and 300 MW hydrogen-cooled domestic turbogenerators have experienced multiple short-circuit accidents at the end of the stator phase since 1983, causing heavy losses. To this end, the Ministry of Electric Power Industry and the Ministry of Machinery Industry issued Anshengji (1994) No. 86, which stipulated the insulation measurement test of the end of the generator handbag as one of the important generator test items. In order to implement the spirit of Document No. 86, before Tangshan China Resources prepared to build a 300MW unit, the hand-wrapped insulation at the end of the stator coil was tested before that the generator does not enter the rotor. Some discussions were held and. some experience has been accumulated.
2? Basic situation
Generate parametersturbine engine
Model QFSN-300-20 Rated capacity 300 MW
Rated voltage 20KV Rated current 10190A
Rated frequency 50Hz Number of phases 3 phases
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Rated speed 3000r/min 2-Y wiring method
Insulation level F Stage cooling method water hydrogen hydrogen
Manufacturer Harbin Electric Machinery Factory?
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Generator stator core
A total of 60 slots, with two metal bars placed in each slot Each metal bar is made up of two rows of braided wires with a mix of hollow and solid wires . Hollow copper is passed through water to cool the windings at the end of the stator coil, two metal bars of the stator are soldered in different slots; together. The vinyl fluoride insulated water pipe is connected to the water collection pipe; six wires are drawn from the stator coil under the stator end cover and connected to the six rings ofoutput via transition wires. The coil insulation is wrapped with multiple layers of epoxy powder mica and epoxy fiberglass cloth. Among them, the handbag insulation of the steam end joint and the excitation end is carried out by the manufacturer before leaving the factory, and the handbag insulation of the lead joint of transition and transition is carried out at the installation site.
3? Test Method
Due to the installation progress, the generator stator cooling water system was not perfect during the test, so we tested the generator water pressure , after the wind pressure and other tests are completed, when the stator coil is not connected to the water, the surface potential positive wiring method is used to test, i.e. that a direct voltage is applied to the three-phase winding of the stator generator at the test voltage of 20KV, and a rodresistance of 100 megohms is used in series with a microammeter. Test the area where the aluminum foil is wrapped and record the microammeter reading.
4? Measuring parts and test standards
(1) Turbine side and exciter side end joints, 60 points each, and the requirement shall not exceed 1900V.
(2) There are 6 wire connectors in total and the voltage should not exceed 1300V.
(3) The transition wire parallel block has a total of 6 points and the voltage should not exceed 1300V. must not exceed 1900 V.
5? Test situation data
In June 2007, we tested the insulation of generator #1 handbag and found that the transition leads to the end of phase B was connected in parallel. The insulation surface potential of the handbag at the block reached 18,000 V, and the discharge was clearly visible when the test rod was close. After gradually reducing the plage of wrapping foil, we finally succeeded. found that the drain was at the insulated water pipe in the upper left corner of the insulation box. After repackaging it passed the test in 2007. In October we carried out a test on the #2 generator handbag insulation and found; that the handbag insulation potential value of the 24-point end connector at the excitation end reached 10,000V, which was qualified after processing by the manufacturer. There are no signs of the above two insulation defects from the appearance, and no obvious problems were found during processing. It can be seen that this testing method is relatively sensitive and effective in detecting defects. Judging by the defects found in both machines, this testing method is also necessary. The final test data is now recorded as follows:
Connector de insulated handbag cable
.Measuring location A 1300
Parallel block of transition cables
Measuring location A X B Y C Z
1# machine voltage (V) 1000 1300 1200 1300 1300 1000
2# machine voltage (V) 1300 1200 1000 1300 1200 1300
Steam and excitation end connector
< p>1 # the machine is between 500V and 1900V, most of them are between 1200V and 1800V; Because the manufacturer added an extra layer of insulating sleeve to the end joint of machine #2, the measured surface potential is significantly reduced, to between 1000 V and 1400 V.
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6. Some experiences and suggestions
In view of the state of insulation of the handbags at the ends of the stator coils of two "turbines" "Minutes of the meeting of "review of measurement methods and standards" Appendix 1 "Measurement methods and judgment criteria", I have some suggestions:
1 Insulated lead jointsand the parallel transition lead blocks are located underneath. The generator end shield. , the test rod is not easy to reach during testing in most places. You can run the wires of these parts before testing, which is more convenient during testing.
2. The generator is notTo perform the test with circulating water, it is necessary to first completely purge the cooling water from the stator. However, how to check whether the cooling water has been blown out can only be achieved by measuring the insulation resistance of the generator, i.e. using a megger to directly measure the insulation of the generator winding to ground, the protection end of the megger is not connected to the water pipe and remains floating. Generally, its insulation value is above 50 megohms.
3. The test equipment required to test when the generator is not connectedwater tee is relatively small. It only requires a high voltage DC generator with a rated output capacity of 2mA. Current measured only 0.5 mA.
4. For testing, simply use a 100 megohm resistance rod in series with a microammeter. There is no need to connect an electrostatic voltmeter to the resistance rod probe, as the microammeter reading is taken. the resistance of the resistance rod The surface potential can be calculated based on the value. Due to the high internal resistance of the electrostatic voltmeter, the parallel connection will not have any effect on the data, but it will cause inconvenience in the test and perform the test. complicated wiring.
5. Once the generator purse is insulated and wrapped, it can be dried for 4-5 days before the surface potential test can be performed. We measured the same piece after 4 to 5 days of drying. drying for 15 days and found that the surface potential was not obvious.
6. Regarding parts wrapped in aluminum foil, the “measuring methods and judgment criteria” are relatively vague and need to be further clarified. During the test, we found that the larger the area wrapped by the aluminum. foil, the greater the measured surface potential value. The smaller it is, it's actually not difficult to understand. The larger the area wrapped by the foil, the smaller the resistance value of the winding to the foil will be. This resistance will then divide the voltage in series with the resistance of the test rod, increasing the measured surface potential. For example, two insulated water pipes and a conductor wire come out of the parallel block of the transition wire if they are packaged as a whole for measurement, the surface potential value mesUrea will be relatively large and difficult to meet standard requirements. Therefore, we divide the joint into three parts for measurement; Similarly, let's divide the joints of the steam end and the exciter end into two parts, the root part and the cone part, for measurement.
In short, this testing method is relatively sensitive and effective in detecting defects, and is worth promoting and using. However, testing methods and standards need to be further clarified and improved.