Power capacitor, used for power system and electrical equipment. Any two metal conductors separated by insulating medium form a capacitor. The capacitance of a capacitor is determined by its geometry and the characteristics of the insulating medium between the two plates. When a capacitor is used under AC voltage, its reactive power is often used to express the capacity of the capacitor, and the unit is var or kilovar.

Power capacitor can be divided into indoor type and outdoor type according to installation mode; low voltage type and high voltage type according to rated voltage of operation; single phase type and three-phase type according to phase number; except for low-voltage shunt capacitor, the rest are single-phase type; metal shell, porcelain insulation shell, bakelite shell, etc. according to shell material.

It can be divided into the following 8 types according to its use:

1) Shunt capacitor. Originally called phase-shifting capacitor. It is mainly used to compensate reactive power of inductive load in power system to improve power factor, voltage quality and line loss.

2) Series capacitor. Series connected in power frequency high voltage transmission and distribution lines, to compensate the distributed inductive reactance of the line, improve the static and dynamic stability of the system, improve the voltage quality of the line, lengthen the transmission distance and increase the transmission capacity.

3) Coupling capacitor. It is mainly used for high-frequency communication, measurement, control and protection of high-voltage power lines, as well as components in the device of extracting electric energy.

4) Circuit breaker capacitor. It was originally called equalizing capacitor. Parallel connection can equalize the voltage on the fracture of EHV circuit breaker, make the voltage between each fracture even during and during the breaking process, improve the arc extinguishing characteristics of circuit breaker, and improve the breaking capacity.

5) Electric heating capacitor. It is used in the electric heating equipment system with the frequency of 40 ~ 24000 Hz to improve the power factor and the voltage or frequency characteristics of the circuit.

6) Pulse capacitor. It is mainly used for energy storage, such as impulse voltage generator, impulse current generator, oscillation circuit for circuit breaker test, etc.

7) DC and filter capacitors. It is used in high voltage direct current device and high voltage rectifying filter device.

8) Standard capacitor. It is used as a standard capacitor or a capacitive voltage divider for measuring high voltage in the circuit of power frequency high voltage measuring dielectric loss.