Experience exchange accident treatment Electrician Technology No. 1 2000 Paper motor, point grounding, praying for this and pragmatic measures Jiangxi Xingan Refined Salt Factory 331302 Gong Binglin 5 AC withstand voltage for coil 3 core and shaft Pressure test, its test 1 Fault phenomenon The motor suddenly generates vibration during operation, and the vibration amplitude gradually becomes larger, and the operation cannot be maintained in less than 1 minute. After the emergency shutdown check, no obvious fault point was found and the operation was restarted. Careful observation, the speed gradually increased until the rated speed, straight and found no abnormal vibration, but when the electrical excitation, the generator set up voltage and boosted to 4 confession, it will produce a wide vibration. Then increase pressure, vibration is more intense. After cancelling the excitation, it returned to normal. Repeat the excitation operation twice.
15,0, the voltage is 6.3.
2 Analysis and treatment According to the above-mentioned fault phenomenon, it is preliminarily determined that the mechanical turbine-containing machine is not required. It is an electrical part. It is highly probable that there is a short-circuit between the rotor pole coils or a two-point grounding corresponding to a partial turn-to-turn short circuit. Due to the existence of a short circuit in the turns, the resistance values ​​of the four poles of the rotor are different, resulting in non-uniform asymmetry of the rotating magnetic field generated. Unbalanced rotation of the rotor causes abnormal vibrations. Then, the generator was disassembled and the rotor of the generator was taken out for inspection.
The insulation resistance of the rotor coil to ground was measured to be zero with 500 megohms, and the insulation resistance of the stator coil to ground and the phase was measured with 250, megohms to meet the specification.
Using force to measure the wide coil as the path, the resistance of the coil to ground is 5000, indicating that the rotor is not broken, but there is non-metallic grounding.
The four-pole DC resistance values ​​of the two double-arm bridges are basically the same, indicating that there is no direct inter-turn short circuit and no metallic grounding exists.
For the four extreme volt-ampere characteristic tests, the characteristic parameters are basically the same, which also indicates that four extremely direct-free wirings are intended to serve as 1.
We use the secondary voltage of the regulator to connect in series 22, and the signal lamp is added between the coil and the shaft, and the voltage is slowly raised to observe the response of the rotor after the voltage is applied. When the voltage rises to 12 hungers, there is a change in the situation, and it is found that there is a discharge arc at point 1 between the magnetic poles 24±; and 23, and at the same time, the series lights. While continuing to pressurize to 4 training sessions, it was found that 21 coils also placed arc light at 1 point of the bushing at the bushing ring. After slightly stabilizing and then boosting to 220, no other discharge points were found. Therefore, it is possible to clearly point and 13 points exist. The non-metallic grounding of the coil, that is, the rotor is grounded at two points.
Because the point is at the bottom of the pole coil close to the core of the core, the main cause of grounding is dirt, resulting in aging of the insulating paint off, and the formation of ground through the dirt. Therefore, for this part, after washing with a series of cleaning agents for electrical cleaning agents, add 23 coats of insulating paint to dry.
For 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 bushings, measure the insulation resistance by 101 and then insulate the entire rotor and stator's electrical parts. Wash and brush the insulation paint properly. After drying, make AC withstand voltage test. Normal . Then the steam supply started without vibration, after the fixed speed, plus excitation voltage, and gradually increased to the rated voltage of 6.3, straight and stable and no abnormal vibration.
In order to prevent the occurrence of the above-mentioned two-point earth fault, we first strengthened the maintenance of the generator, and provided 12-year inspection of the dismantling of the generator, thoroughly cleaned the dirt, ensured that each parameter complied with the specification, and then increased the number of generator rotors. Grounding protection device. Based on the insulation monitoring of the original generator rotor, the zero-line design and installation of the rotor two-point grounding protection device is designed. Its principle 2 is small.
Two-point earthing protection circuit The protective device's action principle is a bridge type, when the turn coil occurs point ground 2, the point can be detected by using the rotor's insulation monitoring device, close the switch and press the button millivolt to Zero, the bridge is in equilibrium.
Then close the switch when closing the switch. Aunt, that is, access to people's current relay coffee, at this time two points of grounding protection that is invested work. Since the bridge is balanced at this time, no current protection circuit in the private relay does not act. When the rotor coil re-occurs the point at the second point of the ground, the resistance is changed due to the fact that the heart is short-circuited, the balance of the bridge is destroyed, and there is current in the coil of relay 01, so that the relay starts its starting current value. According to needs, the relay can be set to act as a signal contact by the test to set the relay's action contact. However, for some special cases, it can also act on the trip and stop. With this protective measure, the turbine generator set can be ensured.
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