Stringing Machine Electrical machinery system
Capacitors in the electrical machinery system for reactive power compensation or phase-shifting use, a large number of installed in the substation at all levels, the normal operation of these electrical machinery capacitors to protect the electrical machinery system power supply quality and efficiency play an important role. The following electrical machinery electrical machinery capacitors in operation should pay attention to the problem and the corresponding treatment methods are described below.
1 ambient temperature electrical machinery capacitors around the ambient temperature can not be too high, nor too low. If the ambient temperature is too high, the heat generated by the capacitor will not be dissipated; and if the ambient temperature is too low, the oil in the electromechanical capacitor may freeze and easily wear. According to the technical conditions of electrical machinery capacitors, electrical machinery capacitors working temperature is generally 40 ℃ to the upper limit. Most of our country's temperature is below this temperature, so usually do not have to use a dedicated cooling facilities. If there is a heat source near the electromechanical capacitor, it is possible to raise the room temperature to above 40 ° C. Ventilation and cooling measures should be taken. Otherwise, the electromechanical capacitors should be removed immediately. The lower limit of the ambient temperature of the electrical machinery capacitor should be determined according to the type and nature of the medium in the electromechanical capacitor. YY-type electrical machinery capacitors in the medium is mineral oil, even below -45 ℃, it will not freeze, so the provisions of -40 ℃ for the lower limit of its ambient temperature. And YL-type capacitors in the medium is relatively easy to freeze, so the ambient temperature must be higher than -20 ℃, the northern region of China should not be used in the winter of this electrical mechanical capacitors. (Unless it is placed indoors and take heating measures)
2 working temperature electrical machinery capacitors work, the internal medium temperature should be lower than 65 ℃, the maximum shall not exceed 70 ℃, otherwise it will cause thermal breakdown, or cause drum phenomenon. Electrical machine The temperature of the capacitor shell is between the medium temperature and the ambient temperature, usually 50 ~ 60 ℃, shall not exceed 60 ℃. In order to monitor the temperature of electrical machinery capacitors, tung oil lime thermometer can be used to paste the probe in the electrical machinery capacitor shell in the middle of the two-thirds height, or the use of melting point of 50 ~ 60 ℃ test wax.
3 working voltage electrical machinery capacitors are very sensitive to the voltage, because the loss of electrical machinery capacitors and voltage square is proportional to the over-voltage electrical machinery capacitors will be serious heat, electrical machinery capacitor insulation will accelerate aging, life shortened, or even electric breakdown. The grid voltage should generally be lower than the rated voltage of the electromechanical capacitor itself, the maximum shall not exceed its rated voltage by 10%, but it should be noted that the maximum operating voltage and maximum operating temperature can not occur at the same time. Therefore, when the working voltage is 1. 1 times the rated voltage, you must take the cooling measures.
4 working current and harmonic problem When the electrical machinery capacitor installed in the magnetic saturation regulator, large rectifier and electric arc furnace and other "harmonic source" of the grid, the AC will appear in the high harmonics. For nth harmonics, the reactance of the electromechanical capacitor will be 1 / n at the fundamental, so the effect of harmonics on the current is very powerful. Harmonic current is very harmful to electrical machinery capacitors, very easy to make electrical machinery capacitor breakdown caused by phase short circuit. Considering the existence of harmonics, it is stipulated that the working current of the electromechanical capacitor should not exceed 1 3 times the rated current. If necessary, should be in the electrical machinery capacitors in series with the appropriate inductive reactance to limit the harmonic current.