Problems should be paid attention to in the operation of power electronic capacitor
As the main power capacitor reactive power compensation or phase shift in power system, a variable is arranged at all levels (with) electric institute.
The normal operation of the capacitor to guarantee the power system of the power supply quality and efficiency play an important role. In the operation of the power capacitor should be paid attention to the problems and the corresponding processing methods are introduced as follows, for the peer reference.
1 ambient temperature
Ambient temperature can not be too high, it can not be too low. If the ambient temperature is too high, the heat generated by the capacitor can not go out; and if the ambient temperature is too low, the oil inside the capacitor may be frozen, easy to electrical breakdown. According to the technical requirements of the capacitor, the working environment temperature of the capacitor is generally the upper limit of 40. In most parts of our country, the temperature is below this temperature, so it is usually not necessary to use special cooling facilities. If there is a heat source near the capacitor, it is possible to make room temperature up to 40 degrees Celsius, this time should be taken to cool the measure, otherwise the capacitor should be removed immediately. The lower limit of the ambient temperature of the capacitor should be determined according to the type and nature of the medium in the capacitor. YY type capacitor in the medium is mineral oil, even in the -45 C below, also won't freeze, so the provisions of -40 C for the lower limit of its ambient temperature. And YL type capacitor in the medium is relatively easy to freeze, so the ambient temperature must be higher than -20.
2 working temperature
When the capacitor works, the temperature of the internal medium should be less than 65, the maximum shall not exceed 70 degrees Celsius, otherwise it will cause thermal breakdown, or cause the phenomenon of drum belly. The temperature of the capacitor shell is between the medium temperature and the ambient temperature, generally 50 to 60 degrees Celsius, not more than 60.
In order to monitor the temperature of the capacitor, available lime paste tung oil will probe the thermometer in the middle of the front 2/3 capacitor shell height, or the use of a melting point of 50 to 60 DEG C test temperature wax to temperature.
3 working voltage
Industrial capacitors are very sensitive to voltage, due to the loss of capacitor and voltage square is proportional to over voltage will cause serious capacitor heating, capacitor insulation will accelerate aging, shorten life expectancy, and even electrical breakdown. Power grid voltage is generally lower than the rated voltage of the capacitor itself, the maximum shall not exceed 10% of its rated voltage, but should pay attention to: the maximum operating voltage and maximum operating temperature can not occur at the same time. Therefore, when the operating voltage is 1.1 times the rated voltage, cooling measures must be taken.
4 working current and harmonic
When the power capacitor to contain magnetic saturation voltage regulator, large rectifier and arc furnace "harmonic" power, AC harmonic will appear. For the N sub harmonic, the capacitor reactance will be the fundamental wave of the 1/n, therefore, the impact of harmonics on the current is very powerful, equivalent to the degree of voltage impact of N2 times. For example, the 5 harmonic, reactive power if it is the 6% fundamental, so it caused voltage only for fundamental rated voltage (1/5) * 6%=1.2%, and it provides high current wave current of 5 * 6%=30% base. Harmonics of this kind of current is very harmful to the capacitor, extremely easy to cause the capacitor breakdown to cause the phase to phase short circuit. Taking into account the existence of harmonics, the provisions of the working current of the capacitor must not exceed 1.3 times the rated current. When necessary, the proper inductive impedance should be connected in series on the capacitor to limit the harmonic current.
5 of the closing arc
Some capacitors especially high voltage capacitor switching in network, because of the surge, on the circuit breaker or the converter will appear on arc. When this kind of situation is encountered, the capacitor value or the replacement of the converter should be adjusted, and the high-voltage capacitor can be eliminated by series reactor.
6 problems in the operation of acoustic
Capacitor at run time, generally is not sound, but sometimes the exception. There are several reasons for the sound:
(1) casing discharge. Casing capacitor assembly type, if the open place for too long, between the two layers of rainwater into the casing, and the voltage, it is possible to produce a lot of discharge sound. At this point, the capacitor and the outer tube outage after discharge discharge, dry reinstall it.
(2) lack of oil discharge. If the capacitor in severe lack of oil, so that the lower end of the casing above the oil level, then there may be issued on acoustic. To this end, the same specifications should be added to the capacitor oil.
(3) Uunsoldering discharge. If there is a capacitor internal weld or sealing, will be in the oil inside the flashover discharge. If you put more than open repair should be sound.
(4) ground discharge. The core and shell contact capacitor is poor, will appear to float voltage caused by acoustic. At this time, as long as the capacitor will be stopped and discharge after processing, the core and the shell has good contact, can make the acoustic disappear.
7 explosion problem
Multiple sets of capacitors in parallel operation, as long as one of them had a breakdown, and the rest of the units will be through this one discharge.
Discharge energy is very large, high pulse power, so that the capacitor oil quickly gasification, causing an explosion, or even fire, it is possible to make the building has also been damaged. In order to prevent such accidents, in each capacitor in series on the appropriate reactor or fuse, and parallel operation.
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