Experience exchange accident handling electrician technology 2000 1st stage leather motor, point grounding, the current treatment and preventive measures Jiangxi Xinkan refined salt factory 331302 Gong Binglin 5 using AC withstand voltage to the coil 3 subway core and shaft for AC resistance Pressure test, test 1 failure phenomenon The motor suddenly generates vibration during operation, and the vibration amplitude gradually becomes larger, and it is impossible to maintain operation in less than 1 minute. After the emergency stop, no obvious fault points were found, so the operation was restarted. Careful observation, the speed gradually increased until the rated speed, no abnormal vibration was found, but when the electric excitation, the generator establishes the voltage and boosts it to 4, it will produce wide vibration. Increase the pressure again and the vibration is stronger. After the excitation is canceled, it is restored to normal. Repeat the excitation twice and the result is the same.
15,0, the voltage is 6.3.
2 Analysis and processing According to the above-mentioned fault phenomenon, it is preliminarily determined that there is no question about the mechanical turbine, and it is the electrical part. However, it is possible that the rotor pole coil has a turn-to-turn short circuit or two-point grounding corresponds to a partial turn-to-turn short circuit. Due to the inter-turn short circuit, the impedance values ​​of the four poles of the rotor are different, resulting in a non-uniform asymmetry of the generated rotating magnetic field. The rotor is unbalanced in rotation, that is, abnormal vibration is generated. Thus, the generator is disassembled and the generator rotor is taken out for inspection.
The insulation resistance of the rotor coil to ground is measured by 500 megaohms, and the stator coil ground and phase insulation resistance are measured in accordance with the specification with 250 megaohms.
Forcefully use the measured wide coil as the path, the coil to ground resistance is 5000, indicating that the rotor is not broken, but there is a non-metallic ground.
The DC resistance values ​​of the four poles are respectively detected by the double-arm bridge, which are basically the same, indicating that there is no direct inter-turn short circuit, and there is no metallic grounding.
The volt-ampere characteristic tests were carried out on the four poles respectively, and the characteristic parameters were basically the same, which also indicated that the four poles had no direct wiring meaning.
We use the secondary voltage of the regulator in series only 22, the signal light is added between the coil and the shaft, slowly increase the voltage, observe the reaction of the rotor after receiving the voltage. When the voltage rises to 12 hunger, there is a change in the condition, and it is found that there is arcing at the point 1 between the magnetic pole 24th; and 23, and at the same time, the light is connected in series. Continue to open the pressure to 4 training, found that the 21 coil at the collector ring at 1 point of the towel also put the arc light, after a little stable and then boosted to 220 did not find other discharge points, so you can clear the point and 13 points The non-metallic ground of the coil, that is, the rotor is grounded at two points.
Since the point is that the pole coil is close to the bottom layer of the core, the main cause of the grounding is that the dirt is large, causing the insulating paint to aging and fall off, and the grounding is formed by the dirt. Therefore, after cleaning the parts with an electric cleaning agent series cleaning agent, add 23 times of insulating paint to dry.
At 8 o'clock, we removed the insulation tube and found that the casing had turned black, resulting in carbonization and grounding. After cleaning and replacing the corresponding casing, shake the insulation resistance to 101 and then insulate and wash the electrical part of the entire rotor and stator. Appropriately brush the insulating varnish. After drying, perform AC withstand voltage test. Normal . Therefore, the steam supply starts to idling without vibration. After the constant speed, the excitation voltage is applied and gradually rises to the rated voltage of 6.3, which is stable and has no abnormal vibration.
In order to prevent the occurrence of the above two-point ground fault, we first strengthen the maintenance of the generator, and stipulate 12 years of disintegration of the generator, thoroughly clean the dirt, ensure that the parameters meet the specifications, and increase the generator rotor two. Point ground protection device. On the basis of the original generator rotor insulation monitoring, the rotor two-point grounding protection device was designed and installed in line 0. The principle 2 is small.
Two-point grounding protection circuit The operating principle of the protection device is the bridge type. When the circuit is turned to the coil, the point is grounded. The point is detected by the insulation monitoring device of the rotor. When the switch is pressed, the button is pressed. Zero, the bridge is in balance.
Then, release the button when you close the switch. Gu, that is, the current relay is connected to the current. At this time, the two-point grounding protection is to work. Since the bridge is balanced at this time, that is, the no current protection circuit in the private relay does not operate. When the rotor coil reoccurs at the point in the ground 2 of the first point, the resistance value changes due to the shorted portion of the core, the bridge balance state is destroyed, and the current in the coil of the relay 01 causes the relay to start its starting current value. It can be applied to the signal signal by the test to adjust the action contact of the 1 relay, but it can also act on the trip and stop for special cases. With this protection measure, the steam turbine generator set can be ensured.
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