Algorithm Simulation And Hardware Realization Of Single Phase-to-earth Fault Location For Small Current Neutral Grounding System

Improve the location precision of single phase-to-earth fault is an important research topic for small current neutral grounding system, the accurate location of fault has important realistic value in eliminating faults rapidly. This paper takes wavelet analysis for the main tool, and proceeding from the angle of improving precision and reliability, it has carried on research to the fault location of the transmission line.This paper mainly includes several parts as follows:At first, it introduces principles of various fault location algorithms, analyzes the principle and application condition of existing various location methods, and points out the applicable scope and limitation of each kind of location method. Because of traveling wave method has a great deal of advantages that high measuring accuracy and do not influenced by transition impedance and grounding types, finally, this paper selects single-terminal traveling wave method to carry on fault location.Second, the theory of mathematical morphology is applied in noise suppression of fault generated traveling waves, the morphological wavelet de-noising algorithm is introduced. Through the MATLAB simulation environment, superiority of the morphological wavelet in terms of filtering noise interference was verifyied. By analyzing the relationship between transmission line structure and transient fault characteristic quantity(The more the bus outlet, the traveling waves are weaker, and traveling waves will be more strongly), extracting current signal to carry on fault location has been adopted. The paper analyzed factors of affecting traveling wave location accuracy's coupling between phases, line sag, wave velocity and other factors, and put forward new method on single-ended traveling waves fault location accuracy which cannot been affected by wave velocity and line sag.Again, in order to verify the accuracy and reliability of this method,simulink simulation model and the fault location computational procedure is established in MATLAB, simulation test for the new method proposed in this paper tests the fault location accuracy under various conditions. Simulation results show that the new method is greatly improved in accuracy ,compared with the original methods.Finally, a set of single-phase grounding fault location device based on current traveling wave is designed . This device uses DSP2407A as its high-speed sampling core unit to capture traveling wave signal of the transient fault current. Use morphological wavelet filter all kinds of noise, then identify the header information of transient current wave through wavelet transform theory,and realize single-ended traveling wave of high-precision positioning. Results of the laboratory simulation test show that the experimental program of this system is truly feasible.End of the paper summarizes the research work carried out, and the subsequent work is prospected.