Design of current protection and automatic reclosing system based on programmable logic controller

Current protection is the most typical relay protection mode for 35kV and below power lines. With the continuous expansion of medium-low voltage distribution network, line current protection has become an important guarantee for reliable operation of the power grid. In order to find a better current protection scheme, this paper proposed the use of programmable logic controller (PLC) to realize three-stage current protection and automatic reclosing of medium-low voltage lines. This design covered the overall design of system structure and function, the hardware design of PLC's peripheral modules and interface circuit, and the software design of the ladder diagram programming. In addition, remote communication technology was introduced, achieving upper computer's configuration monitoring of on-site data. It was verified by the simulation experiment that the system design realized the anticipated function successfully. It can satisfy basic requirements of distribution system's protection and has high reliability in power line's three-stage current protection. (paper)