It is used in electrical equipment and power system . Any two metal conductors separated by a dielectric medium, that is to form a capacitor. The size of the capacitor capacitance, determined by the capacitor itself, the geometry size and the dielectric properties between the two plates. When the capacitor used in the AC voltage, usually expressed the capacity of the capacitor as its reactive power , unit is var or kvar.
In 1926, power capacitors began factory production, and formally used in power system . With the establishment of the large power plants and long-distance transmission system, the development of emerging science and technology, the variety and capacity of power capacitors have been developed rapidly. The early 1950s, the largest capacity of single shunt capacitor is 25 to 50 kvar , to 1978, the largest capacity of single shunt capacitor has reached 6667 kvar, to 1980s , it has reached thousands of kvar