Large Current Of Long-distance Power Supply Monitoring System Design

Due to the increasing of large buildings, rail transportation systems andmechanized mining face in coal mine, the low-voltage power supply system, thebottom and the largest of the grid, continued to expand its power supply distance.In the long-distance power supply system, because the supply line is long, andimpedance is large, so that the short-circuit current of the end of the power supply lineis small. The electric motor is the main load of the grid. When it starts, there will be alarge current surge large, and the value will be several times of the rated current, evenbe greater than the short-circuit current of the power supply end of the line, so thecurrent amplitude protection act will not distinguish. When switching on, traditionalprotection was through improving protective value or increasing protective actions toprevent mis-protection. But both methods reduced the sensitivity of protection. Theyhad been unable to meet the increasingly complex needs of current powersystem.There will be a serious accident, when the power system has a short-circuitfault and the protection trips. On the one hand, the short-circuit will produce heavyelectric current bringing the temperature of power lines very high, and the insulationwill damage or even burn causing a fire burning, but also having a huge electricpower leading the supply equipment destruction;on the other hand, short-circuit willmake the voltage of the other normal lines drop, influencing the use of power, andeven the most serious impact may cause the collapse and disintegration of the entirepower system.The aim of this paper is to design a high-current protection systems forlong-distance power supply. In addition to the basic functions, such as supply andpower control for the supply equipment, the system is able to automatically detect theelectrical parameters of the line in real time to distinguish overload, phase, shortcircuit, under voltage, and motor starting situation. When there is fault in the grid, thesystem could remove power lines, to ensure the safety of persons and equipment. Inaddition, for the difficulty of discovering points of failure in long-distance power, the system adds a function, fault location, to reduce troubleshooting time.At first, this paper analyzes the basic principle of the existing power grid faultdetection methods, and then details the implementation of these principles in thissystem. Then, the article introduces the hardware system design, including PLC, touchscreen and three-phase electrical parameter acquisition module. Software design is animportant aspect of system implementation, the article describes PLC and touchscreen programming, data acquisition, conversion processing, fault alarm and remotedata communication and storage in detail in the fifth chapter. Finally, the articlesummarizes the development process of the system, and discusses the future directionof research and development of high-current monitoring system.