Study On Preventing Override Trip System For High-voltage Power Grid Of Coal Mine Underground Based On The Ethernet

The high-voltage grid of coal mine underground often use unilateral powermultilevel main type system, by many short cable (100~1500m) to form series radialtrunk-type network. Because the impedance of distribution circuit is small, make thebeginning and end of sections of line’s short-circuit current magnitude have smallerdifference, to distinguish the short-circuit protection by current amplitude can’t meetthe requirements of vertical selective, typically. when the lower line short-circuit,short-circuit current exceeds higher-level quick-break protection set value, thehigher-level quick-break protection startup ahead cause Override Trip, causeunderground a big electricity cut, the coal mine production system failures, threat tothe mine and personal safety.The thesis analyzes the reason of power grid of underground Override Tripincident and the existing solution, then analyzes the advantages and disadvantages ofeach solution, and identifies the key of the preventing override trip system is thecommunication network.Based on this situation, the thesis because of switched industrial Ethernet in datacommunication has prominent on the real-time、reliability、etc, puts forward a plan ofthe grid of coal mine underground preventing override trip system based on switchedEthernet. have to add the intelligent interlocking device on each synthetic protectivedevice, as the composition of the interlocking system. If a fault is detected, theintelligent interlocking device delays to activate the quick-break protection (except thelast stage), and send interlocking signals to all upper-level intelligent interlockingdevice over the network at the same time. Each intelligent interlocking device delays10ms to activate the quick-break protection when receive one interlocking signal, toorganize all levels of protection action time, prevent override trip fault, and have backupprotection, reliability well.The next, the thesis makes designs for software and hardware. In the hardware itadopts a89c52SCM as core processor, makes designs for intelligent interlockingdevice and The Ethernet interface circuit. In the software the traditional TCP/IP stackis simplified in the system, and makes designs for the main control program of intelligent interlocking device.In the end, have the calculation of maximum delay in switched industrial Ethernetbased on network calculus, and makes network real-time characteristic simulation byOPNET. The results show that the interlocking protection system can satisfy therequirement of quick-break protection quick-action and selectivity, prevent overridetrip fault.