The design of the integrated device for voltage and reactive power control is introduced. In the device

the nine-section control principle is used in combination with the application of the programmable logic controller. All of the technical requirements in the application for automatization of power substation have been achieved well. The operation function of the touch screen and graphic user interface are also implemented. The transformer tap changer and the capacitor switch can thus be controlled successfully with the cooperation of the PLC to enhance voltage quality and reduce network power loss.