Research On Single-Phase To Ground Fault Selection Technology In Distribution Networks Based On Transient Component

Neutral indirectly grounded way, including Neutral non-grounded way and Petersen-coil grounded way, are widely used in distribution power system in China. Due to the small fault current, unobvious fault features, the complex fault circumstances and the various system run mode, the problem of fault line detection hasn't been well settled.For the sake of obtaining stable and transient features of single-phase-to- ground fault in neutral in directly grounded system, single-phase-to-ground fault transitional quantity are deeply analyzed in this paper.To denoise the fault signal effectively is one of the key technologies of single-phase-to-ground fault selection for distribution network. Based on the deep study of the mathematics morphology elementary theory and primary algorithm, the paper studies that the open and shut combination filtering algorithm carry on denoise of zero sequence current signal. Structural elements is a very important part of mathematical morphology, separately effects on the filtering results for its shape, width, amplitude and so on, and simulation analysis is done for one-dimensional signal. Theoretical analysis and simulation results show that the proposed method can effectively eliminate the noise disturbance, particularly can reduce the influence of the stochastic disturbance.In order to get the sudden change characteristic and the transitional quantity of zero sequence current, and make the sudden change characteristic and the transitional quantity apply effectively in the route selection, this paper proposes one kind of method based on the S transformation of single-phase-to-ground fault transitional quantity route selection for distribution network. Through the S transformation, the paper Obtains multi-dimensional duplicate time-frequency matrix S including the strong message characteristic which includes real part time-frequency matrix and imaginary component time-frequency matrix, and only uses the real part time-frequency matrix extraction the transitional quantity to carry on the route selection. The S transformation combines continual wavelet transformation and the short-time Fourier transformation outstanding thought, overcomes the problem that the short-time Fourier transformation time-frequency window cannot be changed in the time-frequency plane, and does not need to satisfy the wavelet permissibility condition. The theoretical analysis, the single-phase-to-ground fault digital simulation and single-phase -to-ground fault physical analogue experimental result indicate that this method has the better time-frequency resolution and time-frequency localization ability. The algorithm is effectively and accurately can select the fault line.