Research And Implementation Of Faulty Line Detection In Small Current Grounding System Based On STM32

In our country, small current grounding, including the neutral point ungrounding, the arc suppression coil grounding and the high resistance grounding,is widely used in medial voltage distribution system. In small current grounding system, the probability of single phase to ground fault, accounting for more than 80% of all power distribution fault, is very high. The short-circuit current of the fault line is very small, allowing the line to go on running for 1-2 hours according to the relevant regulations. However, if the the fault line continues operating for a long time, it is easy to make the fault worse and expand and affect the whole power distribution system. Therefore, when the system has a single phase to ground fault, the fault line must be timely and accurately found, and isolated or removed out of the system.In this paper, the characteristics of zero sequence current in small current grounding system with single phase to earth fault are analyzed, and the transient and steady state characteristics of zero sequence current are studied. The common method to fault line selection and the applicable range and advantages and disadvantages are summarized On the basis of all the above, a set of economic and practical line detection system based on STM32 is designed which can be used in small and medium sized enterprises. The system adopts the distributed design, data acquisition and data processing are two separately modules, respectively as data acquisition terminal and operation control unit. The CAN bus is adopted for communication of two modules. STM32 series embedded chip has high reliability, real-time performance rich on-chip resources, greatly saving the hardware investment. With the use of advanced embedded technology, data acquisition and processing capacity of the line selection system can be improved. With the field bus technology, the flexibility of system network and the security of data transmission are improved. The two aspects guarantee the efficient and accurate implementation of fault line selection function.