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The neutral point in medium voltage distribution system is mainly non-effectively earthed in China. The important characteristics of this system are the fault-phase voltage decreasing and the un-fault-phase voltage increasing when SLG (Single-Line-to-Ground) fault happened. Due to the existing of line capacitance, the transient progress of un-fault-phase voltage increasing can be regard as a charge...
Distance relays are subject to fail to detect some earth faults since the fault resistance is usually much more in the earth faults rather than the ph-ph faults. Typically a traditional zero-sequence-based method is used to detect a high-resistance earth fault. However, this method fails to detect some high-resistance earth faults. On the other hand, it may trip under normal conditions where there...
The characteristic of single-phase grounding fault and the signal of optimal high frequency region is analyzed in this paper. A new adaptive fault line selection method based on multi-scale wavelet packet decomposition is proposed. Wavelet packet decomposition has excellent focusing property in time-frequency space, besides the method uses multi-scale wavelet packet decomposition rather than fixed...
A method of single phase ground fault line selection in distribution networks with the application of wavelet transform technique is presented in this paper. The modulus maxima of the wavelet transform are extracted to determine the moment of the single phase ground fault. The magnitude and polarity of wavelet transforms, which belong to zero-sequence currents on all lines, are compared to each other...
Due to the reasons of operation and improper maintenance, as well as insulation and et al, the appearance of fault in coal mine is inevitable, while rapidly detect fault can enhance the speed of restoration and improve the stability and reliability of power system. The existing methods of fault location in transmission line are subjected to various conditions, which cause the location result inaccurate...
When single-phase ground fault occurring in distribution network, decomposition scale in which each feeder modulus maximum locate has much difference, because of the complexity of transient component and the effect of system parameter and fault mode. Matrix Mij of modulus maximum is constituted according to each scale maximum value after decomposing zero sequence current by Coiflet4 wavelet. If the...
A novel scheme of single-phase-to-ground fault feeder selection in distribution networks with the application of a wavelet transform technique is presented in this paper. The scheme uses single-phase current traveling wave to identify faulted feeder. The current traveling wave measured by single-phase current transformer of each feeder is decomposed using wavelet multi-resolution analysis. The local...
Coal mine distribution power system is a one-terminal power network which located at the end side of power network. When single phase to ground fault occurs, fault current is too weak to locate the fault position. In order to solve this problem, a new algorithm is presented, which uses the difference of wave velocity between ground mode component and aerial mode component of traveling wave that arrives...
Through a small current grounding system of single-phase grounding to steady state and transient analysis and the existing line selection methods are analyzed and compared, their advantages and shortcomings can be gotten. The line of the selection method in the future was pointed out. The wavelet analysis was introduced to selection methods of faults and the fault lines can be selected in the wavelet...
The faults due to leaning trees are common in Nordic Distribution networks. In [1], the detection of this fault type has been discussed and the faulty section has been estimated using a novel selectivity technique. This detection was based on an absolute sum of Discrete Wavelet Transform (DWT) detail coefficients of the residual voltages. The detection selectivity function depended on the transient...
In this paper, the initial transients in the electrical network due to arc reignitions associated with high impedance faults caused by leaning trees are extracted from phase voltages and currents. The discrete wavelet transform (DWT) is used for the fault feature extraction corresponding to band frequency 12.5- 6.25 kHz and therefore localizing this fault occurrence. The detection security is enhanced...
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