The Research Of Single-phase Earth Fault Detection In Distribution Network

In electric system, single-phase earth fault occupy whole defective 60% upwards.In an given situation, the security of electric system is only decided by the work mode of neutral point.In our country, power distribution system of 6～35kv extensively useing isolated neutral system or by extinction coil grounded undercurrent earthed system mode of connection,This thesis analysis the characteristic of each mode of connection, and taking the study of neutral point earthed by parallel connection of small resistance and extinction coil which is widely used.As for undercurrent earthed system, when single-phase earth fault occurs, the short-circuit current is not high enough to endanger the safety of equipments and system, line voltage of the system is still symmetry, and keep on transporting power to users,But the major defect is:When single-phase earthing occurs, other phase voltage rises, intermittence malfunction can bring transient high voltage, it is tend to stimulate a dangerous phasetophase fault, So in this system, when single-phase earthing occurs, we should find out the grounded circuit in time, and excise the fault line as soon as possible,There are some study towards single-phase fault, but they all based on malfunction route selection in busbar end,The orient to defect point is also based on busbar end, like traveling wave ranging.This thesis analysis different kinds of test method of undercurrent earthed system when single-phase fault occurs, and bring forward different kinds of method to estimate the fault occurs before or behind the test station,In this thesis pay attention to the system which neutral point is grounded by parallel of resistence and extinction .This system can open the fault line rapaidly and can give failure message clearly . Also introduces two filter methods: fir and fft. Then based on the active component theory, design a device which can collect sampling by wireless communication and proceed data processing by TMS320VC5402,The hardware part of this thesis introduces periphery sample circuit,conditioning circuit and other circuits with TMS320VC5402, Introduces algorithm based on phase comparison, as well as algorithmic flow chart to implement hardware,This thesis introduces the emulation by matlab, By using SimpowerSystem emulation component library, I have constructed an undercurrent earthed system to demonstrate some kinds of measuring method,NN kit and customed filter module can help to proceed confirm the parameter in algorithm, these aided design slickly demonstrate the feasibility of algorithm and be large action to optimize the program,...