The role of reactive power compensation and capacitor characteristics (2)

Reactive power compensation capacitors are capacitive reactive power supplies that operate for long periods at industrial frequency AC voltages. The reactive power loss of the reactive power compensation capacitor itself is small and generally accounts for about 0.3% to 0.5% of the reactive power. The power capacitor is easy to install, easy to use, and has a small amount of maintenance work. It requires less investment at a time. Due to the structural characteristics, excessive ambient temperature and operating voltage will affect its practical performance and life, and even cause accidents. The reactive output of a capacitor is proportional to the square of the voltage. When the system voltage is reduced and more reactive power compensation is required, the reactive power output of the power capacitor is reduced at this time, revealing its insufficient performance. The power capacitor is a means of reactive power compensation in the power system. The capacitive current of the shunt capacitor in operation cancels the inductive current and reduces the reactive power response in transmission elements such as transformers and lines. Therefore, it not only reduces the flow due to reactive power, but also reduces the reactive power. The active loss also reduces the voltage loss and increases the power factor.

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Therefore, the use of shunt capacitors for reactive power compensation at all levels of the grid is the most widely used method of power system. Reasonable selection and application of reactive power compensation Capacitors The selection of the capacitor's rated capacity should be matched with the transformer's capacity. It is difficult to obtain a reasonable supplement effect if the rated capacity of the capacitor is too large or too small. Prevent frequent switch of capacitor switch. The frequent switching of the capacitor switch will produce a very high peak current. The peak current is very harmful to the normal operation of the switch electrical, which often results in the shortened service life of the switch or sudden failure of the damage. Prevents capacitors from being affected by harmonic resonances. Connecting an inductive reactor in series with the capacitor's connection loop prevents both resonance and high-order harmonic currents. Determining reactive power compensation capacity The purpose of the reactive power compensation calculation is to rationally select the capacity of the shunt capacitor. The choice of capacitor mounting capacity can be determined by factors such as the purpose of use, increasing the operating factor by improving the power factor, and reducing the line loss.

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Determining the compensation capacity from the viewpoint of improving the power factor is the most common method. In addition to the formula calculation, in practice, you can also use the checklist to obtain the active power and power factor per 1kW to improve the required compensation capacity before and after. Multiply the monthly average active power of the maximum load to calculate the required reactive power compensation capacity. The compensation capacity is determined by increasing the line terminal voltage. According to the regulation of reactive voltage, the power factor of the power supply at the sending end is preferably 0.95~0.98. Generally, the purpose of the terminal voltage drop is not large. The compensation capacity is determined from the perspective of improving the power supply capacity of substations.