KWB(W) High-voltage reactive power automatic compensation device is widely used in power systems and industrial and mining enterprises distribution networks of 6-10kV, 50Hz . It is applicable to parallel capacitor devices and transformer load tap changer of all levels of 6-110kV substations both the new and extension. By dividing the capacitors into different groups, capacitors are switched automatically according to the demand of the reactive power. Composite control of reactive power and voltage are achieved through adjusting the taps of the transfoemer. The above methods make it reality to improve the power factor, decrease the line loss, improve and enhance the quality of system voltage.