Abstract
Since weak fault signals often lead to the misjudgment and other problems for faulty line selection in small current to ground system, this paper proposes a novel faulty line selection method based on variable scale bistable system (VSBS). Firstly, VSBS is adopted to analyze the transient zero-sequence current (TZSC) with different frequency variety scale ratio and noise intensity, and the results show that VSBS can effectively extract the variation trends of initial stage of TZSC. Secondly, TZSC is input to VSBS for calculation with Runge-Kutta equations, and the output signal is chosen as the characteristic currents. Lastly, correlation coefficients of every line characteristic current are used as the index to a novel faulty line selection criterion. A large number of simulation experiments prove that the proposed method can accurately select the faulty line and extract weak fault signals in the environment with strong noise.
Highlights
As an important part of the power system, distribution network is closely associated with its users and has direct impact on the users
Select the faulty line according to the proposed method, and the parameters of variable scale bistable system (VSBS) are as follows: a = b = 1 and compression-scale ratio (CR) = 1500
For waveform, the changing trend of initial stage waveform in Figure 8(a) is clearer than that in Figure 8(b), indicating that VSBS can better describe the changing trend of transient zero-sequence current (TZSC) compared to wavelet packet transform, because when the initial value is 0, the brown particles are in potential peak position of bistable system, and any small disturbance will make the brown particles of bistable system move drastically, so the bistable system can well track the signal changing trend
Summary
As an important part of the power system, distribution network is closely associated with its users and has direct impact on the users. Data show that 80% of fault occurring in distribution network is single phase-to-ground fault. When single phase-to-ground fault occurs, the line voltage value is still symmetrical, the fault current is weak, and it could run 1 to 2 hours after fault occurs, which significantly improves the reliability of power supply. During the single phase-to-ground fault period, nonfault phase voltage could rise, which will threaten the system insulation and result in interphase shortage, protection tripping, power supply outage, and other problems. Because of the weak fault signal and the harsh working condition, faulty line selection becomes difficult. It is necessary to carry out further research in this area [1, 2]
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