Transformation Of Main Transformer Cooler System Based On PLC Control

To actively promote the "intensified management of three components and integrated systems of five processes" system construction advocated by SGCC,500kV substations are gradually moving to the direction of the less personified and unmanned. Reducing the operating personnel is bound to make higher request for the reliability of the equipments. Due to the traditional electromagnetic relay control used by the main transformer cooler of some500kV substation in Taizhou city, there has been many problems in operation, such as the high failure rate of components, simple realization of the functions and design flaws. In order to improve the operational reliability of the main transformer cooler and take this opportunity of the main transformer overhaul, the transformational program of main transformer cooler system has been proposed, which is based on PLC control. Choosing Siemens S7-200(CPU226) as a programmable logic controller (PLC),taking the upper oil temperature and load of the main transformer as control conditions and using software programming, the cooler control system can control the main transformer cooler fans and oil pump’s intelligent cutting.The paper analyzes the problems and design flaws of the original main transformation cooler system in AC power circuits, AC control circuits, cooler full stop circuits and box auxiliary circuits, and puts forward the transformational programs one by one. By use of dual redundant configuration of PLC and peripheral circuits based on solid-state relays, the transformed main transformation cooler system can achieve six flexible cooler operating modes. The author designs the peripheral circuit and gives a detailed analysis of those modes according to PLC control. At the same time, simple human-computer interaction can be realized by using Siemens S7-200and TD200communications and the remote monitoring of cooler operation status can also be achieved with the communications of the monitoring background. After it is put into operation, the transformed cooler control system runs well. Therefore, the purpose of that transformation is achieved.