A power distribution terminal waveform acquisition time synchronization correction method

Abstract

The present application relates to a kind of power distribution terminal waveform acquisition time synchronization correction method.It includes: S1-proportional transformation, the waveform data of power distribution terminal acquisition is converted from electrical secondary value to electrical primary value, eliminate the influence caused by different mutual inductor ratio of power distribution terminal, make the waveform between different terminal more comparable;S2-eliminate noise, filter high-frequency noise in signal, obtain the signal after removing noise;S3-waveform interpolation, waveform data is interpolated, ensure that the signal sampling point number of each waveform is consistent in a cycle;S4-time correction, using the waveform after interpolation, waveform is translated on time axis and compared, obtain the waveform after synchronization correction.The present application method can realize waveform time synchronization correction, and can eliminate abnormal signal acquisition and realize the function of synchronous time checking.

Description

Technical Field

[0001] This invention relates to the field of power distribution automation technology, and in particular to a method for correcting the timing synchronization of waveform acquisition in power distribution terminals. Background Technology

[0002] Single-phase grounding faults are the most frequent type of fault in distribution networks, and also the most difficult to diagnose. Currently, distribution terminals collect electrical quantity information such as zero-sequence voltage and zero-sequence current on-site, and use algorithms such as the first half-wave method, zero-sequence power method, and phase current mutation method to diagnose single-phase grounding faults on-site. However, due to limitations such as high-resistance grounding, insufficient information sources from a single terminal, and small zero-sequence current after compensation by the arc suppression coil in the station, the accuracy of the diagnosis is low, and the problem of misdiagnosis and missed diagnosis of faults often occurs.

[0003] To improve the accuracy of single-phase grounding fault assessment, a technical approach has been adopted where transient waveform recording fault indicators acquire waveforms from the field at the terminal. The main station or substation-side aggregation unit collects electrical quantity information from all in-station and out-of-station distribution terminals under the same busbar at the same substation. This centralized assessment algorithm replaces the previous method of on-site assessment by distribution terminals, achieving some success. However, existing centralized assessment algorithms are based on synchronous acquisition technology. All transient waveform recording fault indicators participating in centralized assessment must have BeiDou or GPS time synchronization capabilities with high accuracy. This means that distribution terminals lacking BeiDou or GPS time synchronization capabilities, or with insufficient time synchronization accuracy, cannot participate in centralized assessment, especially the large number of existing distribution terminals in the field. If existing distribution terminals are to participate in centralized assessment, corresponding hardware modules must be installed and the software algorithm updated, resulting in extremely high modification costs. This limits the pilot application of synchronous acquisition-based centralized assessment technology for single-phase grounding faults to large-scale deployment. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by providing a method for correcting the time synchronization of waveform acquisition in power distribution terminals. Without modifying the power distribution terminals, this method is developed into a corresponding software algorithm module and deployed on the main station side or the substation side aggregation unit. This enables the electrical quantity waveforms acquired by all in-station and out-of-station power distribution terminals under the same substation and the same busbar to be aligned in time, thereby indirectly achieving synchronous acquisition.

[0005] After a single-phase ground fault occurs on the line, the collection unit on the main station side or the substation side begins to collect electrical waveforms from the line selection device inside the substation and the power distribution terminal outside the substation. At this time, the waveform is affected by the internal clock error of the device, and the sampling time may deviate from the actual time. If the waveform is aligned with the sampling time as a reference, there will be deviations, which will affect the accuracy of the single-phase ground fault centralized judgment algorithm. Therefore, waveform acquisition time synchronization correction is required.

[0006] To achieve the above objectives, the technical solution of the present invention is: a method for correcting the time synchronization of waveform acquisition in a power distribution terminal, comprising:

[0007] Step S1, Proportional Transformation: Convert the waveform data collected by the distribution terminal from electrical secondary values ​​to electrical primary values ​​to eliminate the influence of different transformer ratios in the distribution terminal and make the waveforms of different terminals more comparable.

[0008] Step S2: Noise Filtering: Filter high-frequency noise in the signal to obtain the noise-removed signal;

[0009] Step S3, Waveform Interpolation: Perform interpolation on the waveform data to ensure that the number of signal sampling points for each waveform is consistent within one cycle;

[0010] Step S4, Time Correction: Using the interpolated waveform, the waveform is shifted on the time axis and compared to obtain the waveform after synchronization correction.

[0011] In one embodiment of the present invention, in step S2, high-frequency noise in the signal is filtered using a low-pass filter or Fourier transform / wavelet transform techniques to obtain a noise-removed signal, thereby avoiding the impact of high-frequency noise signals on subsequent processing.

[0012] In one embodiment of the present invention, in step S3, an interpolation algorithm is used to interpolate the waveform so that the number of sampling points and the sampling time interval are consistent in each period of all waveforms.

[0013] In one embodiment of the present invention, in step S4, since the amplitude and phase of electrical quantity signals at any position of all feeders under the same busbar in the same substation at the same time have a certain similarity, the waveform is translated on the time axis by waveform spectrum analysis or by defining an electrical quantity signal similarity function. The similarity function value of the waveform is calculated when the waveform is translated by different distances on the time axis. When the similarity function value reaches the maximum value, the waveform is considered to be aligned, that is, the waveform after synchronization correction is obtained.

[0014] In one embodiment of the present invention, a threshold is set for the similarity function. If the similarity function value of a certain group of signals is lower than the threshold with other signals, it is considered that the group of signals has an acquisition abnormality and will not be used in subsequent algorithms to avoid the acquisition abnormal signals affecting the overall judgment accuracy of the system.

[0015] In one embodiment of the present invention, the similarity function is defined as follows:

[0016]

[0017] In the formula, u 01 u 02 Let n be the zero-sequence voltage of the two waveforms that need to be aligned, and n be the number of sampling points involved in the calculation. The waveforms are translated on the time axis, and the similarity function values ​​at different translation times are calculated. When the similarity function value reaches its maximum value, the waveforms are considered to be aligned.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) Achieve waveform time synchronization correction. The waveform acquisition time synchronization correction method proposed in this invention for distribution terminals can be developed into a corresponding software algorithm module and deployed on the main station side or the substation side aggregation unit without modifying the distribution terminals. This enables the electrical quantity waveforms acquired by all in-station and out-of-station distribution terminals under the same substation and the same busbar to be aligned in time, thereby indirectly achieving synchronous acquisition. The modification cost is small and the method is highly scalable.

[0020] (2) Eliminating Abnormal Signals. The waveform signals acquired by the power distribution terminal may be abnormal due to factors such as component aging, wiring errors, and data packet loss. In designing the similarity function, this invention can set a corresponding threshold. If the similarity function value of a certain group of signals is lower than the threshold compared to a large number of other signals, then the acquisition of that group of signals is considered abnormal, and the group of signals will no longer be used in subsequent algorithms, thus avoiding the impact of abnormal signals on the overall accuracy of the system's judgment.

[0021] (3) Synchronization time synchronization function verification. For some distribution terminal equipment that is already equipped with a time synchronization module and has synchronous acquisition function, the waveform acquisition time synchronization correction method of the distribution terminal proposed in this invention can verify the synchronous time synchronization function of the distribution terminal at the main station or at the substation aggregation unit. When the synchronous time synchronization function of the distribution terminal fails, an early warning is issued. At the same time, the waveform data acquired by the distribution terminal with the synchronous acquisition function failure can still participate in the centralized analysis of single-phase grounding faults, thereby improving the reliability of system waveform alignment. Attached Figure Description

[0022] Figure 1 This is a system flowchart of an embodiment of the present invention.

[0023] Figure 2 This is a flowchart illustrating the specific algorithm for noise filtering in an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the waveform interpolation and alignment method according to an embodiment of the present invention. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] To make the features and advantages of this patent application more apparent and understandable, specific embodiments are provided below, along with accompanying drawings, for detailed explanation:

[0028] like Figure 1 As shown, this implementation proposes a method for correcting the time synchronization of waveform acquisition in power distribution terminals. Without modifying the power distribution terminals, this method is developed into a corresponding software algorithm module and deployed on the main station side or the substation side aggregation unit. This achieves time alignment of electrical quantity waveforms acquired by all in-station and out-of-station power distribution terminals under the same substation and busbar, indirectly realizing synchronous acquisition. The specific technical solution is as follows:

[0029] After a single-phase ground fault occurs on the line, the collection unit on the main station side or the substation side begins to collect electrical waveforms from the line selection device inside the substation and the power distribution terminal outside the substation. At this time, the waveform is affected by the internal clock error of the device, and the sampling point time may deviate from the actual time. If the waveform is aligned with the sampling point time as a reference, there will be deviation, which will affect the accuracy of the single-phase ground fault centralized judgment algorithm. Therefore, waveform acquisition time synchronization correction is required.

[0030] Furthermore, waveform acquisition time synchronization correction includes the following steps:

[0031] Step S1: Proportional Transformation. The waveform data collected by the distribution terminal is converted from electrical secondary values ​​to electrical primary values, eliminating the influence of different transformer ratios in the distribution terminal and making the waveforms between different terminals more comparable.

[0032] Step S2: Noise Removal. High-frequency noise in the signal is filtered using a low-pass filter, or techniques such as Fourier transform or wavelet transform, to obtain a noise-removed signal, thus preventing high-frequency noise from affecting subsequent processing.

[0033] like Figure 2 As shown, in this embodiment, step S2 specifically includes the following steps:

[0034] Step S2-1: Signal decomposition. Wavelet transform is used to process the waveform, decomposing it into high-frequency and low-frequency signals.

[0035] Step S2-2: Signal processing. Reduce or zero out the coefficients of some high-frequency signals to reduce the impact of high-frequency noise on the signal.

[0036] Step S2-3: Signal Reconstruction. The signal is reconstructed using a signal reconstruction algorithm to obtain the noise-removed signal.

[0037] Step S3: Waveform interpolation. The number of sampling points within one period of the waveform requiring alignment is N1, N2, N3, N4, ..., N. i Calculate N1, N2, N3, N4, ..., N i The least common multiple N is used as the target number of sampling points within one period of each waveform. A linear interpolation algorithm is employed to expand the number of sampling points within one period of all waveforms to N, such as... Figure 3 As shown.

[0038] Step S4, Time Correction: Since the amplitude and phase of voltage waveforms at any location on all feeders under the same busbar in the same substation at the same time have a certain similarity, especially the zero-sequence voltage waveform, the similarity function is defined as:

[0039]

[0040] In the formula, u 01 u 02 Let be the zero-sequence voltages of the two waveforms that need to be aligned, and n be the number of sampling points involved in the calculation. The waveforms are translated along the time axis, and the similarity function values ​​are calculated at different translation times. The waveforms are considered aligned when the similarity function value reaches its maximum value.

[0041] Furthermore, a threshold can be set for the similarity function. If the similarity function value of a certain group of signals is lower than the threshold with a large number of other signals, it is considered that the acquisition of that group of signals is abnormal, and the group of signals will no longer be used in subsequent algorithms to avoid the acquisition of abnormal signals affecting the overall judgment accuracy of the system.

[0042] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0043] This patent is not limited to the above-described preferred embodiments. Anyone can derive other forms of methods for correcting the timing synchronization of waveform acquisition in power distribution terminals based on the inspiration of this patent. All equivalent changes and modifications made within the scope of this patent application shall fall within the scope of this patent.

Claims

1. A method for correcting the time synchronization of waveform acquisition in a power distribution terminal, characterized in that, include: Step S1, Proportional Transformation: Convert the waveform data collected by the distribution terminal from electrical secondary values ​​to electrical primary values ​​to eliminate the influence of different transformer ratios in the distribution terminal and make the waveforms between different terminals more comparable. Step S2: Noise Filtering: Filter high-frequency noise in the signal to obtain the noise-removed signal; Step S3, Waveform Interpolation: Perform interpolation on the waveform data to ensure that the number of signal sampling points for each waveform is consistent within one cycle; Step S4, Time Correction: Using the interpolated waveform, the waveform is shifted on the time axis and compared to obtain the waveform after synchronization correction; In step S3, an interpolation algorithm is used to interpolate the waveforms to ensure that the number of sampling points and the sampling time interval are consistent for all waveforms in each period. In step S4, by defining an electrical quantity signal similarity function, the waveform is translated on the time axis, and the similarity function value is calculated when the waveform is translated by different distances on the time axis. When the similarity function value reaches its maximum value, the waveform is considered to be aligned, that is, the waveform after synchronization correction is obtained. A threshold is set for the similarity function. If the similarity function value of a certain group of signals is lower than the threshold with other signals, the group of signals is considered to have an acquisition anomaly and will not be used in subsequent algorithms to avoid the acquisition anomaly affecting the overall judgment accuracy of the system. The similarity function is defined as follows: In the formula, , These are the zero-sequence voltages of the two sets of waveforms that need to be aligned. To determine the number of sampling points involved in the calculation, the waveform is translated along the time axis, and the similarity function value is calculated at different translation times. When the similarity function value reaches its maximum value, the waveform is considered to be aligned.

2. The method for correcting the time synchronization of waveform acquisition in a power distribution terminal according to claim 1, characterized in that, In step S2, high-frequency noise in the signal is filtered out using a low-pass filter, Fourier transform, or wavelet transform to obtain a noise-removed signal, thus avoiding the impact of high-frequency noise on subsequent processing.

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