Abstract : This paper introduces a PLC intelligent reactive power compensation device, details the system scheme using the device, and presents the hardware and software composition of the system. It also provides a detailed explanation of the data acquisition, processing, protection, and interlocking procedures. The feasibility of this scheme is further demonstrated in practical applications. Keywords : reactive power; intelligent reactive power compensation device; programmable controller 0. Introduction Some users in the Changpo substation under Kunming Power Company have long power supply radii, thin wire diameters, heavy loads, and large voltage drops. The voltage of users at the first end of the substation is below the lower limit, but the voltage of users at the end is also below the lower limit. In order to keep the voltage within the acceptable range and reduce grid losses, it is necessary to strengthen the construction of reactive power sources in the grid, that is, to optimize the configuration of reactive power compensation capacitors to achieve local reactive power balance [1-3]. However, in some substations, manual reactive power compensation devices are used, which are labor-intensive and difficult to accurately judge and switch on and off in a timely manner. The main problems are: (1) "Switching oscillation" is very likely to occur. Under a certain load condition, when a group of capacitors is switched on, the power factor exceeds the upper limit of the specified limit; when the group of capacitors is switched off, the power factor is lower than the lower limit, so repeated switching occurs. (2) "Switching method" is unreasonable. Most of them adopt the "sequential switching" method, which makes the capacitor bank in front often in the running state, while the switching switch of the later one often operates, shortening the service life of the capacitor bank. (3) The operation mode is uneconomical. The manual switching method is difficult to control the switching frequency, which easily leads to resource waste and is uneconomical. This paper adopts an intelligent reactive power compensation device composed of a microcomputer programmable controller (PLC) and a host computer to replace the manual compensation device. The operation effect after the transformation is significant and the above problems are solved. Download the full text of the planning of intelligent reactive power compensation device based on PLC .