Optimization and reconstruction of the main circui

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Optimization and transformation of main circuit of capacitor connection

Abstract: This paper introduces the method of small circuit breaker replacing traditional fuse as protective capacitor, which is simple and applicable

key words: capacitor connection circuit breaker capacitor contactor in recent years, the use of capacitor low-voltage centralized compensation in small substations has played an important role in power supply capacity, power quality and loss reduction. However, in the actual operation, some problems have also been exposed, especially the serious problem of reactive power compensation, which does not achieve the purpose of the lighting measurement method GB 5699 (85) for the reasonable compensation of electric reactive power. Combined with the actual situation of reactive power compensation in small substations, the existing problems with improving the independent innovation ability of the plastic processing industry as the core are analyzed. The original capacitor distribution cabinet adopts the wiring mode of fuse + contactor + thermal relay + capacitor, which often leads to fuse burnout, single-phase open circuit, three-phase open circuit, and even fire caused by heating. Many factories used this method. 1. The permanent deformation and temporary deformation of the leaf spring after strong pressure treatment should not be greater than 0.5mm, which once caused the capacitor fire accident. Fortunately, it was found in time and did not cause large losses. This kind of accident is mainly caused by the fact that when the fuse is switched on or off the capacitor, the passing current is times the rated current, the overload capacity of the fuse is poor, and it is easy to heat up. Long term operation causes one or three-phase open circuit, which brings potential safety hazards to the distribution system. On the other hand, when there are harmonics in the electricity, the terminal voltage increases after the capacitor is put into operation, and the current through the capacitor increases more, which increases the loss power of the capacitor. For film paper composite dielectric capacitors, although the allowable loss power with harmonics is 1.38 times that without harmonics; For the full film capacitor, the allowable loss power with harmonics is 1.43 times that without harmonics. However, if the harmonic content is high and exceeds the allowable conditions of the capacitor, the capacitor will be overcurrent and overloaded, and the loss power will exceed the above value, causing the capacitor to heat abnormally, and the insulation medium will accelerate aging under the action of electric field and temperature. Especially when the capacitor is put into the electricity whose voltage has been distorted, it may also aggravate the harmonic of the electricity, that is, produce the phenomenon of harmonic expansion. In addition, the existence of harmonics often makes the voltage present a spike waveform, and the spike voltage wave is easy to induce partial discharge in the medium. Due to the large rate of voltage change and the high intensity of partial discharge, it can accelerate the aging of the insulating medium, thereby shortening the service life of the capacitor. Generally speaking, for every 10% increase in voltage, the service life of the capacitor will be shortened by about 1/2. Moreover, in the case of serious harmonic, it will also make the capacitor bulge, breakdown or explosion. After many times of analysis, comparison and test, the small air circuit breaker (c65n Series) is used to replace the traditional alloy as a simple modified breaker, which improves the safe operation ability. It has strong making and breaking capacity. In case of overcurrent and short circuit, the three phases will trip at the same time, cutting out the fault point to ensure the safe operation of the capacitor. This method has been used in the plant for more than a year, and it runs well without abnormal problems

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