Study On The Selective Electrical Leakage Protection System Based On Timing Sequence Authenticated In Coal Mine Low Voltage Supply Grid

At present, the low voltage levels power grid of many coal mine has been increased to 1140V,3300V from 380V.With voltage increasing power supply failure appears more frequently, and single-phase grounded leakage fault takes up nearly 80%, this paper is mainly concerned with single-phase grounded leakage fault. As the power supply system's reliability, economy and other requirements are higher, protection devices demand more and more selectivity, so this paper mainly focuses on the selective leakage of underground low voltage power supply protection system.This paper firstly makes the theoretical analysis about single-phase grounded leakage fault in underground low voltage supply network and make some necessary simulation, provide the necessary theoretical support to the system design. Also analyze several current popular line selection, such as additional DC detection principle, the principle contrasting zero sequence current phase, zero-sequence power direction principle, the direction of zero sequence current active component principle, timing sequence authenticated principle, make the theory analysis and carried out contrast, choose the appropriate line selection for the system.According to the current situation of the low-voltage supply network of mine, the paper used a two-stage communication style of selective leakage protection system that can simultaneously proceed longitudinal and latitudinal protection, use the RS485 communication of superior protection and lower protection to complete the bus and branch protection, the security is guaranteed. Superior protection of the system used AT89C51 as a controller for monitoring the insulation level of the grid; Lower protection selects Actel's ProASIC3 A3P250 chip as the controller, complete the selective protection principle, select the fault branch. In addition, some external aid hardware was designed, including analog quantity acquisition module,signal processing module,fault indication and alarm module,on-off output module,power supply module and RS485 communications module.Finally, because the coal mine has many interference sources, interfere is very serious, so, this paper adopts the Anti-interfere measures of hardware and software aspects, the measures designed can meet the system's Anti-interfere requirements. The paper last gives the simple analysis of two main error sources in the system, and provides the appropriate solution.