Before removing the fuse, first turn a microcomputer reactive power compensation controller switch on the capacitor cabinet to the off state (the contactor loses power and disconnect the capacitor) and then turn the knife switch on the capacitor cabinet to the off state (cut off the capacitor cabinet power supply) Then start disassembling the job. First check the contactor and each of the Zhuangtou conditions for abnormalities, and then remove the capacitor for observation and testing.
The main reason that can cause the fuse to blow:
1. High harmonics in the power grid
2. Capacitor resonance
3. Other factors that can cause the fuse to blow due to overcurrent of the capacitor:
Defective fuse
2. Poor contactor
3. Controller abnormality After analyzing the above several factors and then combining the actual use environment, the pre-operation analysis is started. The capacitor cabinet on the main transformer side of the power distribution room has a certain usage time. The microcomputer is not working. The controller is also very old. Compared with another capacitor on the main transformer side of No. 2, the difference is quite large. The other is the digital tube display program and the other is the intelligent program displayed on the LCD meter. The No. 1 main transformer side capacitor cabinet has no reactor, and the capacitor cabinet on the main transformer side of No. 2 is equipped with a reactor mainly for filtering high harmonics for the power grid.
For the removed capacitor (to be removed corresponding to the group of blown fuses), it is necessary to visually check whether there is obvious bulging phenomenon, oil leakage and sealing failure, and internal corona breakdown discharge. The fuse should be replaced with a new fuse of the same specification, and the test of the contactor and each of the tops is checked and the test is started. (http:// copyright)
In the power-on and closing sequence, first turn the knife switch on the capacitor cabinet to the combined state (for the capacitor cabinet power supply) and then turn the microcomputer reactive power compensation controller switch to the manual gear state to the set of capacitors to be tested (contactor Power action) This will start measuring the capacitor current.
From the measured working current situation of this group, it is within the rated range, and there is basically no abnormality on the circuit. Analysis of the capacitor removed from the appearance of the appearance of the obvious bulging oil leakage phenomenon, but from the side, the shell is a little S-shaped button (a few cases of heat deformation??) and then test with a shake table (Requires measurement of 500 volts and above) Because the shaking table at hand has been broken for a long time (although the multimeter can also be roughly measured but not shaken), the following is the theoretical test method for shaking table test:
500 volt insulation shake test method:
1. Remove all connections to be tested and discharge before being tested.
2. The object to be measured should be in good insulation when shaking.
3. Pass the test leads to the capacitor electrode reliably.
4. Measure the resistance of the three terminals of the capacitor to the case.
5. After the generator is charged for a certain period of time and the data is read, the test line should be quickly removed from the test object to cut off the circuit, so as to avoid the residual charge of the charged capacitor from discharging through the circuit inside the shaker. Drop and break the indicator pin and burn internal components such as the diode inside the shaker.
After the test, the results are judged:
1. When the table is shaken, the needle gradually increases from zero to a certain value and tends to be stable. When the capacitor is short-circuited after shaking, there is a clear sound and spark of the discharge, indicating that the capacitor has good charge and discharge performance, as long as the insulation is not lower than the regulation. The value can be judged that the capacitor is qualified and can be put into operation with confidence.
2. If the shaker has some readings, but there is no discharge spark when shorted, it means that the connecting wire between the electrode plate and the terminal has broken, and it must be taken out of operation or replaced with a new capacitor.
3. If the shaker is stopped at the zero position, it indicates that the inside of the capacitor has broken down and must be taken out of operation or replaced with a new capacitor.
Test with a multimeter:
1. Measure the insulation resistance. First discharge the capacitor's residual power to the three terminals of the capacitor. After the multimeter is electrically blocked, hit the M-European gear and then measure the resistance of the terminal to the casing with the test leads. The resistance is not less than M. In principle, the higher the resistance value, the better. Note that after each terminal is measured, the three terminals are discharged separately.
2. Insulation resistance measurement between phase and phase, the terminal should be discharged before the measurement, and the universal meter is electrically blocked to the M-European range, and then the resistance value between the terminals is measured by the meter and the time is measured. After a little time of observation, the resistance value is read out until the needle is no longer changed. Generally, the resistance value is in the M-class, and the performance is worse than the M-class or the insulation is poor. The terminals are discharged after each measurement, and the resistance measurement between the phases and phases cannot be measured with a remote meter and only a multimeter can be used.
3. Discharge the terminals before the measurement of the phase-to-phase charge time. After the universal meter is blocked by K, the meter is separately measured between the two terminals, and the change of the resistance reading is observed. The required value from 0 to the maximum resistance (the maximum resistance when the reading does not change) is recorded. Time, in theory, the longer the time, the better. If the resistance does not change from 0, then this capacitor must be very poor performance. It is also important to note that the terminals are discharged after each measurement.
According to the above and some tests of the comprehensive research, the main cause of the fuse blown this time is the poor overcurrent of the capacitor harmonic high capacitor.
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Shenyang Zhicheng Heavy Machinery Manufacturing Co., Ltd. , https://www.zhichengmachinery.com