Method for line selection and positioning

Abstract

The invention discloses a method for line selection and positioning, which can eliminate interference and has high precision and wide application. The method utilizes the most prominent advantages of Prony algorithm as follows: modal damping factors in signals can be analyzed; sampling and Prony fitting can be performed on failure instantaneous current of a plurality of lines on failure to obtain precise failure data; failure line selection is performed by a Fourier decomposition-wavelet analysis method because the polarities of all zero-sequence current sudden changes of non-failure lines are the same and the polarities of zero-sequence current sudden changes of a failure line and non-failure lines are opposite, so that the failure line can be accurately identified; and after the failure line is identified, an injection method is utilized for failure positioning and failure positioning is realized by injection signals characteristics and detection and track of routes. The method has the characteristics of interference elimination, high precision and wide application, thereby being of high popularization value.

Description

technical field [0001] The invention relates to the technical field of grid operation fault diagnosis, in particular to a line selection and positioning method. Background technique [0002] There are many system grounding methods commonly used in power systems: neutral point grounding directly, neutral point not grounding, neutral point grounding through arc suppression coil, neutral point grounding through resistance. In the GB / T 4776-1984 standard of "Electrical Safety Terminology", the above four neutral point grounding methods are classified into two categories: the neutral point effective grounding system (system with effectively earthed neutral): the neutral point is directly grounded or Connect to ground via a low value resistor. This type of system can also be called a large grounding current system; neutral point non-effectively grounded system (system with non-effectively earthed neutral): the neutral point is not grounded or grounded through a high-value impedan...

AI Technical Summary

Problems solved by technology

[0004]The current main line selection method: the steady-state zero-sequence current amplitude and phase comparison method cannot exclude the influence of CT unbalanced current and transition resistance; steady-state harmonics Compared with the current direction method, the 5th harmonic content is much smaller than the fundamental wave, and the value is very small, which is easy to be mixed with interference components, and the measurement accuracy is not easy to guarantee; the 5th harmonic component method may have harmonic sources in the system itself. And when the load is asymmetrical, especially when there is a phase-to-phase short circuit or a three-phase short circuit in the system, a large number of 5th harmonics will be generated due to the saturation of the components of the measurement circuit, which will inevitably make the judgment line criterion based on the harmonic component comparison method fail. The effect of the device using the 5th harmonic component for fault line selection is not ideal; the wavelet packet fuzzy neural network model and algorithm have strict restrictions on the selection of samples, and the fault modes in various situations should be considered when selecting samples. The application is limited; the Prony fitting method, the Prony algorithm can extract the attenuation characteristics and phase characteristics of the signal, so if the fault instantaneous current of multiple lines can be sampled and Prony fitted, and then their phase and phase characteristics can be compared The attenuation characteristics can be used to find the faulty line. However, due to the relatively large amount of calculation of the Prony algorithm itself and the need for complex high-order matrix operations, this analysis method cannot be effectively promoted. At the same time, because the algorithm is very sensitive to the influence of noise, In the background of interference noise, the strict solution of this model is a highly nonlinear optimization problem, which also greatly limits the application of the Prony model; based on the method of wavelet analysis, the polarity of the zero-sequence current mutation of all non-fault lines is the same , the polarity of the zero-sequence current mutation of the fault line is opposite to that of the non-fault line zero-sequence current mutation polarity. Based on this, the fault line can be judged. The network used has fast convergence speed, excellent robustness, and is not subject to load harmonics. However, this method has strict restrictions on the selection of samples, and the failure modes in various situations should be considered when selecting samples, which is limited in practical applications; S injection method Since the single-phase ground fault is mostly intermittent arc grounding, the transition resistance varies in a large range. When the grounding arc resistance is large, it is in the interval When it is equal to the capacitive reactance generated by the distributed capacitance, it is very difficult to select the line, and it is easy to misjudgment and miss judgment.

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