First half-wave positioning method suitable for high-resistance grounding

Abstract

The invention discloses a method for positioning a first half wave under a high-resistance grounding condition. The method comprises the following steps of: preprocessing data; performing phase locking calculation; generating a difference value sequence; carrying out gradient analysis and interval identification; performing interval verification; and interval output. The invention belongs to the technical field of power system fault detection, particularly provides a first half wave positioning method suitable for high-resistance grounding, and solves the problems of noise interference, high sampling cost, poor nonlinear distortion adaptability, weak high-resistance grounding signals and the like in the prior art through an innovative signal processing means.

Description

Technical Field

[0001] This invention belongs to the field of power system fault detection technology, specifically referring to a first half-wave localization method applicable to high-resistance grounding. Background Technology

[0002] The first half-wave of the transient signal for a single-phase ground fault (i.e., the current / voltage waveform within the first half-wave cycle of the power frequency after the fault occurs) is the core basis for fault location. At the instant of grounding, the zero-sequence current undergoes a sudden change, and its waveform amplitude attenuation, polarity reversal, and time-frequency characteristics are directly related to the location of the fault point. Especially in systems where the neutral point is not effectively grounded, the transient energy of the first half-wave is significantly higher than that of the steady-state signal, which can overcome the sensitivity limitations of traditional steady-state location methods. In the case of high-resistance grounding, the fault current is limited, and its amplitude is significantly lower than that in the case of metallic grounding. Its rising edge gradient may be reduced due to the damping effect of the high resistance.

[0003] First-half-wave localization involves locating the start and end points of the first half-wave within a segment of zero-sequence current or voltage signal that includes the abrupt change in signal at the moment of grounding, thus obtaining the interval where the transient signal is relatively obvious. However, the application of first-half-wave localization technology in practical engineering faces multiple challenges:

[0004] 1. Noise interference problem: In the distribution network, power electronic equipment, distributed power lines and line stray capacitance cause high-frequency noise to be mixed with fault traveling waves, and traditional wavelet transform or correlation analysis methods are difficult to accurately extract the traveling wave front;

[0005] 2. Sampling cost limitation: Positioning based on traveling wave method requires synchronous sampling devices with high sampling rate, but the distribution network has long lines and many nodes, making the deployment cost of high-precision equipment unbearable;

[0006] 3. Nonlinear distortion effect: Faults such as arc grounding and intermittent grounding cause severe distortion of the first half-wave waveform, causing the positioning algorithm based on fixed threshold or template matching to fail.

[0007] While existing solutions (such as S-transform time-frequency analysis and deep learning waveform recognition) have partially alleviated the above problems, they still have certain limitations:

[0008] Time-frequency analysis algorithms have high computational complexity and are difficult to meet the real-time positioning requirements of power distribution networks; deep learning models rely on massive amounts of fault data for training and have poor generalization ability for unseen grounding scenarios.

[0009] To address the aforementioned pain points, there is an urgent need for a first-half-wave positioning technology that balances accuracy, real-time performance, and cost-effectiveness. This technology should overcome technical barriers such as noise interference, sampling rate limitations, and nonlinear adaptability through innovative signal processing methods and lightweight intelligent algorithms. Summary of the Invention

[0010] In view of the above situation and to overcome the shortcomings of the prior art, the present invention provides a first half-wave positioning method suitable for high-impedance grounding. Through innovative signal processing methods, it solves the problems of noise interference, high sampling cost, poor nonlinear distortion adaptation and weak high-impedance grounding signal in the prior art.

[0011] The technical solution adopted in this invention is as follows:

[0012] This invention discloses a first half-wave localization method suitable for high-impedance grounding, comprising the following steps:

[0013] Step S1: Determine the number of sampling points X for one power frequency cycle using a phase-locked loop algorithm;

[0014] Step S2: Take two consecutive sampling points R from the sampled data sequence {R} at an interval of X. n R n+X , denoted as A1 n A2 n That is, A1 n =R n A2 n =R n+X These two sampling points are in phase between two consecutive cycles, R n Let {R} be the nth sampling point in the sequence {R}; slide the values ​​of the recorded waveform data to obtain two sampling sequences {A1} and {A2};

[0015] Calculate the difference sequence {D} between {A1} and {A2}, where Dn = A2. n -A1 n =R n+X -R n ;

[0016] That is, take A11, A21, A12, A22, A13, A23...A1 from the sequence {A1}, {A2} in sequence. n A2 n By taking the difference, we obtain the sequence {D} = D1, D2, D3...D n ;

[0017] Step S3: Identify the continuous rising and falling intervals in the difference sequence {D};

[0018] If the maximum value of the interval exceeds the set threshold M, and its length is within the range of [3, X / 4], it is determined to be a valid transient mutation interval;

[0019] Step S4: Take the starting point of the rising interval as the starting point of the first half wave, and the ending point of the falling interval as the ending point of the first half wave.

[0020] Furthermore, the sampled data sequence {R} is the waveform data of zero-sequence current or zero-sequence voltage.

[0021] Furthermore, the phase-locked algorithm is a PLL (phase-locked loop) algorithm.

[0022] Furthermore, the calculation of the difference sequence {D} includes subtracting the sequence {A1} and {A2} point by point.

[0023] Furthermore, the identification of the rising and falling intervals is achieved through first-order difference operations.

[0024] Furthermore, the gradient threshold of the first-order difference operation is dynamically set based on the maximum value of the sampled data.

[0025] Furthermore, the set threshold M is 5 times the steady-state sample value.

[0026] Furthermore, the method also includes preprocessing the raw sampled data, the preprocessing including moving average filtering.

[0027] On the other hand, this application also discloses a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method described above.

[0028] On the other hand, this application also discloses a first half-wave positioning system, including a processor and a memory, wherein the memory stores a computer program, and the processor executes the program to implement the above-described method.

[0029] The beneficial effects achieved by the present invention using the above solution are as follows:

[0030] 1. By using periodic differential to suppress power frequency periodic noise, highlight transient changes, improve the signal-to-noise ratio, and enhance wavefront recognition capabilities.

[0031] 2. Positioning can be achieved with only a standard sampling rate, which can reduce hardware requirements and save deployment costs.

[0032] 3. Based on gradient change, it identifies abrupt change intervals without a fixed threshold, and has strong robustness to waveform distortion.

[0033] 4. By amplifying weak transient changes through periodic differential amplification, the detection sensitivity under high-resistance grounding is enhanced.

[0034] 5. The algorithm has low complexity, requiring only addition, subtraction, and comparison operations, and can complete positioning in milliseconds, meeting real-time requirements. Attached Figure Description

[0035] Figure 1 This is a flowchart of a first half-wave positioning method applicable to high-resistance grounding according to the present invention.

[0036] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, this invention provides a first half-wave positioning method applicable to high-impedance grounding.

[0039] Taking zero-sequence current data as an example, the specific implementation process is as follows (zero-sequence current sampling rate Fs = 12800Hz, power frequency F0 = 50Hz):

[0040] S1 Data Preprocessing: The raw waveform recording data is denoised using a moving average filter.

[0041] S2 phase-locked calculation: The number of power frequency sampling points X = Fs / F0 = 256 is determined using the PLL phase-locked algorithm;

[0042] S3 difference sequence generation:

[0043] The zero-sequence current sampling sequence is {I}, and point A1 is taken. n =I n A2 n =I n+256 Calculate the difference D n =A2 n -A1 n =I n+25 -I n ;

[0044] S4 gradient analysis and interval identification:

[0045] Perform a first-order difference operation on {D}: ▽D n =D n+1 -D n ;

[0046] Set a gradient threshold to determine the rising edge (starting point) and falling edge (ending point):

[0047] Check the starting point of the rising edge: the first one that satisfies ▽D n >0.1×max(|I n |) five consecutive sampling points, starting from the Sth sampling point;

[0048] Check the falling edge end point: The first sampling point that meets ▽D n <0.01×max(|I n |), and the end point is the E-th sampling point;

[0049] Interval verification: For the interval (D S , D E ) identified in step S4, find the maximum value M and calculate the interval length L.

[0050] (D S , D E ) is the part between the S-th sampling point and the E-th sampling point in the sequence {D}.

[0051] Set the threshold T = 5 times the steady-state sampling value, and the length limit is 3 to 64 (X / 4).

[0052] When M>T and 3<L<64, the marked interval is considered valid.

[0053] S5 Interval output: Mark the waveform segment [S, E] between the start point (rising edge start point) and the end point (falling edge end point) of the valid interval verified in step S4 as the first half-wave interval, corresponding to the sampling data sequence (I S , I E ), that is, the part between the S-th and the E-th sampling points in the zero-sequence current sampling sequence {I}.

[0054] As can be seen from the above, the calculation of the present invention is relatively simple, the hardware cost is low, and only the zero-sequence voltage / current data captured by a conventional recording and broadcasting device can be used to find the first half-wave interval, providing a reliable basis for subsequent fault location.

[0055] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0056] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

[0057] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for locating the first half-wave of a high-impedance grounded circuit, characterized in that, Includes the following steps: Step S1: Determine the number of sampling points X for one power frequency cycle using a phase-locked loop algorithm; Step S2: Take two consecutive sampling points R from the sampled data sequence {R} at an interval of X. n R n+X , denoted as A1 n A2 n That is, A1 n =R n A2 n =R n+X These two sampling points are in phase between two consecutive cycles, R n Let {R} be the nth sampling point in the sequence {R}; slide the values ​​of the recorded waveform data to obtain two sampling sequences {A1} and {A2}; Calculate the difference sequence {D} between {A1} and {A2}, where D n =A2 n -A1 n =R n+X -R n ; Step S3: Identify the continuous rising and falling intervals in the difference sequence {D}; If the maximum value of the interval exceeds the set threshold M, and its length is within the range of [3, X / 4], it is determined to be a valid transient mutation interval; Step S4: Take the starting point of the rising interval as the starting point of the first half wave, and the ending point of the falling interval as the ending point of the first half wave.

2. The first half-wave localization method for high-impedance grounding according to claim 1, characterized in that: The sampled data sequence {R} is the waveform data of zero-sequence current or zero-sequence voltage.

3. The first half-wave localization method for high-impedance grounding according to claim 1, characterized in that: The phase-locked algorithm is a PLL (phase-locked loop) algorithm.

4. The first half-wave localization method for high-impedance grounding according to claim 1, characterized in that: The calculation of the difference sequence {D} involves subtracting the points from the sequences {A1} and {A2} one by one.

5. The first half-wave localization method for high-impedance grounding according to claim 1, characterized in that: The identification of the rising and falling intervals is achieved through first-order difference operations.

6. The first half-wave localization method for high-impedance grounding according to claim 5, characterized in that: The gradient threshold for the first-order difference operation is dynamically set based on the maximum value of the sampled data.

7. The first half-wave localization method for high-impedance grounding according to claim 1, characterized in that: The set threshold M is 5 times the steady-state sample value.

8. The first half-wave localization method for high-impedance grounding according to claim 1, characterized in that: The method further includes preprocessing the raw sampled data, the preprocessing including moving average filtering.

9. A computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method as described in any one of claims 1-8.

10. A first half-wave positioning system, comprising a processor and a memory, wherein the memory stores a computer program, and the processor executes the program to implement the method as described in any one of claims 1-8.

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