A fast identification method for short-circuit faults of adjacent lines with non-local voltage levels based on db4 wavelet decomposition
A voltage level, line short-circuit technology, applied in the fault location and other directions, can solve the problem of inability to reliably determine the short-circuit fault of adjacent lines of non-local voltage level
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Embodiment 1
[0053] Example 1: Establish as figure 1 In the simulation system model shown, the transformer is a three-phase transformer with △ / y connection, and its parameters are as follows: the rated capacity is 600MVA, and the rated transformation ratio is 220kV / 525kV.
[0054]Now assume that a phase A ground fault occurs on the 220kV side of the transformer in the line TLineM2, and the ground resistance is assumed to be 0. Under this model, the voltage data of each phase is as follows figure 2 shown. The db4 wavelet transform is performed on the data in the 2ms time window after the start-up of each phase device respectively, and the absolute value sequence of the high frequency component at the first scale of each phase under such a fault is calculated as follows: image 3 shown. Integrate the absolute value sequence obtained by each phase, and use the maximum value function to obtain the maximum value of the three-phase integral value, 0.0439. Its logarithm value is greater than ...
Embodiment 2
[0055] Example 2: Establish as figure 1 The parameters of the simulated system model shown are described in detail in Embodiment 1, and will not be repeated here. Now assume that a three-phase short-circuit fault occurs on the 220kV side of the transformer in the line TLineM2. Under this model, the voltage of each phase is as follows: Figure 4 shown.
[0056] Select the data in the time window within 2ms after the device starts to perform db4 wavelet transformation, and obtain the absolute value sequence of the high-frequency components at the first scale of each phase under such a fault, such as Figure 5 As shown, the absolute value series obtained for each phase were integrated respectively, and the maximum value was taken as 0.0593. It is known from Example 1 that the logarithm is obviously greater than or equal to -2. According to the criterion, it is determined that the 220kV side line has a short-circuit fault, which is consistent with the assumption and the judgment...
Embodiment 3
[0057] Example 3: Establish as figure 1 The parameters of the simulated system model shown are described in detail in Embodiment 1, and will not be repeated here. Now assume that the 220kV side of the transformer in the line TLineM2 operates normally. Under this model, the voltage of each phase is as follows: Image 6 shown.
[0058] Select the data in the time window within 2ms after the device starts to perform db4 wavelet transformation, and obtain the absolute value sequence of the high-frequency components at the first scale of each phase under such a fault, such as Figure 7 As shown, it is approximately zero. Integrate the absolute value sequence obtained for each phase, and take the maximum value of 3.1378e-07. Its logarithmic value must be less than -2. According to the criterion, it is judged that the 220kV side line is operating normally, which is consistent with the assumption and the judgment is correct.
[0059] The following table is the statistical data whe...
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