Capacitance compensation is reactive power compensation or power factor compensation. Reactive power will be generated when the electrical equipment of power system is used, and it is usually inductance. It will reduce the efficiency of power supply capacity, and can be improved by adding capacitance properly in the system.

The rated voltage of the capacitor should not be lower than the maximum operating voltage of the capacitor connected to the power grid. When the capacitor is connected to the series reactor to reduce harmonics, the voltage on the capacitor terminal will be higher than the grid voltage. At this point, the capacitor with higher rated voltage should be selected. It is important to set aside an appropriate safety margin when selecting the rated voltage, as the voltage on the dielectric is inappropriately increased, and the characteristics and life of the capacitor will be adversely affected. Attention should be paid to the operating temperature and ambient temperature of the capacitor because it has a great influence on the service life of the capacitor. The electrochemical aging of the dielectric will be accelerated when the temperature exceeds the upper limit. Therefore, when the ambient temperature can not meet the requirements, effective cooling measures should be taken. If the cooling temperature can not be improved, special designed or higher rated voltage capacitors must be used.