Analysis And Research Of Single-phase Grounding Fault Line Selection In Current Grounding System

With the increasing development of China’s power distribution system,its degree of intensification has deepened,which makes the probability of failure increase,especially single-phase ground fault.Neutral point ungrounded systems and neutral arc-suppression coil grounding systems are used in distribution networks.Due to their special grounding methods,fault signals are weak and residual currents are small when single-phase ground faults occur in the system.Causes frequent mis-selection of conditions during a fault,which seriously affects the reliability of the power supply.Aiming at the above problems,this paper proposes a new fault line selection method based on modulus maxima of wavelet domain.Through experimental verification,this method can not only overcome the situation of misjudgment,but also simplify the calculation process.It has important theoretical significance and application value.In this paper,before establishing the line selection scheme,the characteristics of the single-phase grounding faults in the small-current grounding system are firstly analyzed in depth,and the characteristics of the steady-state components and the transient components of the system and the relevant electrical characteristics are summarized.It shows that the transient component has more research value than the steady state component.The criterion is in the original wavelet.Improvements were made on the basis of line selection and transient component selection,and the squared difference of the modulus maximum value was selected to judge.This simplifies the calculation process and improves the line selection accuracy.Secondly,according to the line selection principle of this paper,we design the line selection process,select the appropriate wavelet function,and then use MATLAB/Simulink software to build fault models with different grounding modes.Through the simulation analysis of different types of failures,the results show that the line selection scheme is designed in this paper.It can solve the problem of insufficient accuracy,low sensitivity and slow response rate of ground faults in the original power supply system.It is an effective line selection scheme.Finally,in the design of the line selection device,the line selection device is designed for the small current grounding system by analyzing the functions and requirements of the line selection device.Then,the hardware structure and software structure of the line selection device are analyzed in general and for different modules.The detailed design of the function,through the experimental verification,proved the effectiveness of the line selection device in this paper.