Research Of Selectivity Leakage Protection For Under-ground Low Voltage Power Supply System

The leakage is one of the main failure forms of underground power supply system. Not only does it cause physical electrocution accident, it can also produce electric spark which can cause gas and dust explosion accidents and electric detonator explosion accidents. The mine environment on the low voltage power grid is bad, therefore the leakage protection is put forward the requirements of reliability, quick acting and selectivity. The leakage protector must select the real leak and tripping immediately. It must remove the function of the fault line accurately. This system adopted a scheme which based on three leakage protection principles of detection.In total controller, this system adopts the additional DC power supply. The branch feeder switch adopts zero sequence current amplitude protection and zero sequence power direction. The communication link of this system using optical fiber transmission of information to improve the data transmission ability of the system for realizes the rapid communication of leakage protection. This approach will transmit the branch processer data to the total controller rapidly, it also can prevent misjudgment or wrong judgment effectively. The main switch and branch switch of this system all chooses DSP (TMS320F28335) as the controller. The total controller and the branches processor use the master-slave mode based on CAN bus to communication with each other. The system can choose any processor as the general controller through the keyboard, so that we can effectively avoid the total controller problem caused by accidents. This method can avoid the failure of the leakage effectively. Through the design of hardware circuit and software programming method, this system can judge the leakage fault and choice the leakage branch correctly. The system’s anti-interference design from two aspects of hardware and software design by all aspects can improve the running practicality of the leakage in the underground environment. The system simulation confirmed that the system has three advantages, which are high reliability, high sensitivity and accurate ability to choose the leakage.