Single-phase-to-ground Fault Line Detection In Non-effectively Earthed Neutral System Based On Agent

Non-effectively earthed neutral system is widely used in power distribution system below 66kV in China.The non-effectively earthed neutral system has many merits.First of all,as its fault current is small,the system would not incur short circuit despite single-phase-to-ground fault.Further,it brings no harm to people or electric equipments,nor has any effect on the capability of the electricity network as the line voltage remains stable.However,the non-effectively earthed neutral system easily gives rise to wrong detection of the fault line due to the small fault current and unobvious fault features in case of single phase-to-ground fault.Especially for the arc-suppression coil grounded system,as the residual current of the grounded point on fault line is small and the phase varies,the detection of the fault line in arc-suppression coil grounded system is more difficult to achieve.Regarding the difficult problems stated above,the thesis thoroughly researched and analyzed the stable and transient features of single-phase-to-ground fault in neutral non-effectively earthed system in theory.The thesis analyzed the inadequacy of the existing fault line selection and clarified the criteria of fault line detection which are mainly based on wavelet.In addition,a fault line detection device established on the basis of multi-agent system is set forth,which can divide agents of the system by their levels and functions.MAS arbitration is proposed in comprehensive utilization of various fault line detection methods.Finally,the thesis introduced the hardware design of the MAS-based fault line detection and discussed how to achieve MAS system usingμC/OS.