A power distribution network distributed traveling wave distance measurement terminal and a fault current identification method

Abstract

The application belongs to the field of power distribution network fault detection, and provides a power distribution network distributed traveling wave distance measurement terminal and a fault current identification method, which comprises power network line traveling wave current data acquisition, first-order difference calculation, first average power calculation, second average power calculation, to-be-judged ratio calculation and operation state judgment. The application identifies the fault current through whether the ratio of the second average power to the first average power is suddenly changed, can effectively avoid the interference of noise, and improves the sensitivity of fault current identification.

Description

Technical Field

[0001] This invention relates to the field of distribution network fault detection, and in particular to a distributed traveling wave ranging terminal for distribution networks and a fault current identification method. Background Technology

[0002] Distributed traveling wave ranging terminals for distribution networks are installed on distribution lines to record traveling wave current data generated during distribution network faults. The ranging terminals upload the recorded traveling wave data to a data center station via a wireless network. The data center station uses a two-end positioning principle to calculate the fault location based on the uploaded, timestamped traveling wave data. Generally, the traveling wave sampling channels of monitoring terminal devices filter out the 50Hz power frequency component. The traveling wave uses a threshold triggering principle; when the high-frequency traveling wave amplitude exceeds a certain threshold, the system is triggered to record the line current for a certain period.

[0003] However, when there are harmonics or significant terminal noise in the distribution network, the interference noise and harmonics may enter the traveling wave channel, potentially causing the traveling wave amplitude to exceed the threshold value, resulting in false triggering. Increasing the threshold value to address false triggering might prevent some minor faults from triggering properly, increasing the probability of missed detections. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a distributed traveling wave ranging terminal for power distribution networks and a fault current identification method. The fault current is identified by whether the ratio of the second average power to the first average power changes abruptly, thereby avoiding noise interference and improving the sensitivity of fault current identification.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for fault current identification in a distributed traveling wave ranging terminal of a distribution network includes:

[0007] The traveling wave current data of the distribution network lines is collected using a pre-set distributed traveling wave ranging terminal for the distribution network.

[0008] First-order differential calculation is performed on the traveling wave current data of the distribution network line to obtain a differential dataset;

[0009] The average of the squares of the first P data points in the differential dataset is calculated to obtain the first average power; P is the number of data points before the traveling wave current data of the distribution network line is collected.

[0010] The average of the squares of the (P+1)th to (P+Q)th data points in the differential dataset is calculated to obtain the second average power; Q is the number of data points after the traveling wave current data of the distribution network line is collected.

[0011] Calculate the ratio of the second average power to the first average power to obtain the ratio to be judged;

[0012] When the ratio to be judged is less than the mutation threshold, the traveling wave current data of the distribution network line is non-line fault data;

[0013] When the ratio to be judged is greater than the mutation threshold, the traveling wave current data of the distribution network line is the traveling wave data of the line fault.

[0014] Preferably, the calculation formula for the differential dataset is: Δx(n) = x(n+1) - x(n); where Δx(n) is the nth data in the differential dataset; and x(n) is the nth data in the traveling wave current data of the distribution network line.

[0015] Preferably, the mutation threshold value is 1.5.

[0016] Preferably, the traveling wave current data of the distribution network line is collected using a pre-set ranging terminal, including:

[0017] The target line is coupled using the Rogowski coil inside the ranging terminal to obtain the original analog current data;

[0018] Integrating the original analog current data yields reconstructed analog current data;

[0019] The reconstructed analog current data is high-pass filtered to obtain filtered analog current data;

[0020] The analog current filtering data is converted from analog to digital to obtain the traveling wave current data of the distribution network line.

[0021] Preferably, a distributed traveling wave ranging terminal for a power distribution network includes: a Rogowski coil, an integrating current, a filter circuit, a high-speed ADC, a controller, and a 4G communication module connected in sequence.

[0022] The Rogowski coil is used to couple the target line to obtain raw analog current data; the integrating current is used to integrate the raw analog current data to obtain reconstructed analog current data; the filtering circuit is used to perform high-pass filtering on the reconstructed analog current data to obtain filtered analog current data; the high-speed ADC is used to perform analog-to-digital conversion on the filtered analog current data to obtain traveling wave current data of the distribution network line; the controller is used to determine the fault status of the target line based on the traveling wave current data of the distribution network line to obtain fault data; the 4G communication module is used to upload the fault data to a pre-set data center station.

[0023] The present invention discloses the following technical effects:

[0024] This invention provides a distributed traveling wave ranging terminal for power distribution networks and a fault current identification method. The fault current is identified by whether the ratio of the second average power to the first average power changes abruptly, which solves the defect of traditional fault current identification that is prone to false triggering and realizes reliable and sensitive identification of fault current. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the fault current identification process provided in an embodiment of the present invention;

[0027] Figure 2 A flowchart for fault current identification provided in an embodiment of the present invention;

[0028] Figure 3 This is a diagram of a distributed traveling wave ranging terminal module for a power distribution network provided in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of false triggering data caused by line harmonics provided in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of accidental touch data caused by device noise, provided in an embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram of actual fault data for recording metallic grounding faults provided in an embodiment of the present invention.

[0032] Figure 7 This is a schematic diagram of actual fault data for tree obstacle fault records provided in an embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The purpose of this invention is to provide a distributed traveling wave ranging terminal for power distribution networks and a fault current identification method. The fault current is identified by whether the ratio of the second average power to the first average power changes abruptly, thereby avoiding noise interference and improving the sensitivity of fault current identification.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 This is a schematic diagram of the fault current identification process provided in an embodiment of the present invention. Figure 2 A flowchart for fault current identification provided in an embodiment of the present invention is shown below. Figure 1 and Figure 2 As shown, this invention provides a method for fault current identification in a distributed traveling wave ranging terminal of a distribution network, comprising:

[0037] Step 100: Collect traveling wave current data of distribution network lines using a pre-set distributed traveling wave ranging terminal for the distribution network;

[0038] Step 200: Perform first-order differential calculation on the traveling wave current data of the distribution network line to obtain the differential dataset;

[0039] Step 300: Calculate the average of the squares of the first P data points in the differential dataset to obtain the first average power; P is the number of data points before the traveling wave current data of the distribution network line is collected;

[0040] Step 400: Calculate the average of the squares of the (P+1)th to (P+Q)th data points in the differential dataset to obtain the second average power; Q is the number of data points after the traveling wave current data of the distribution network line is collected;

[0041] Step 500: Calculate the ratio of the second average power to the first average power to obtain the ratio to be judged;

[0042] Step 600: When the ratio to be judged is less than the sudden change threshold, the traveling wave current data of the distribution network line is non-line fault data;

[0043] Step 700: When the ratio to be judged is greater than the sudden change threshold, the traveling wave current data of the distribution network line is the traveling wave data of the line fault.

[0044] Specifically, the calculation formula for the differential dataset is: Δx(n)=x(n+1)-x(n); where Δx(n) is the nth data in the differential dataset; and x(n) is the nth data in the traveling wave current data of the distribution network line.

[0045] Preferably, the mutation threshold value is 1.5.

[0046] Specifically, the traveling wave current data of the distribution network lines is collected using a pre-set ranging terminal, including:

[0047] The target line is coupled using the Rogowski coil inside the ranging terminal to obtain the raw analog current data;

[0048] Integrating the original analog current data yields the reconstructed analog current data;

[0049] High-pass filtering is applied to the reconstructed analog current data to obtain filtered analog current data;

[0050] Analog-to-digital conversion is performed on the filtered analog current data to obtain the traveling wave current data of the distribution network line.

[0051] refer to Figure 3 A distributed traveling wave ranging terminal for power distribution networks includes: a Rogowski coil, an integrating current, a filter circuit, a high-speed ADC, a controller, and a 4G communication module connected in sequence.

[0052] The Rogowski coil is used to couple the target line to obtain the original analog current data; the integrating current is used to integrate the original analog current data to obtain the reconstructed analog current data; the filtering circuit is used to perform high-pass filtering on the reconstructed analog current data to obtain the analog current filtered data; the high-speed ADC is used to perform analog-to-digital conversion on the analog current filtered data to obtain the distribution network line traveling wave current data; the controller is used to determine the fault status of the target line based on the distribution network line traveling wave current data to obtain fault data; and the 4G communication module is used to upload the fault data to the pre-set data center station.

[0053] Specifically, the distributed traveling wave ranging terminal of the distribution network collects the traveling wave current of the distribution network line in real time. The traveling wave current refers to the high-frequency transient current of the power frequency of 50Hz after filtering out the current. When the traveling wave current is detected to meet the triggering conditions, the traveling wave recording process will be triggered. Finally, the terminal sends the recorded data to the data center station for fault location calculation.

[0054] Furthermore, the specific identification process is as follows:

[0055] The ranging terminal mainly consists of components such as a Rogowski coil, integrating current, filtering circuit, high-speed ADC, controller, and 4G communication module.

[0056] The Rogowski coil is mainly used to couple the line current. Its basic principle is to integrate the line current and convert it into a small current that can be collected and processed in the second step.

[0057] The integrating circuit integrates the secondary voltage of the Rogowski coil to reconstruct the current characteristics of the circuit.

[0058] The filter circuit is usually a high-pass filter circuit, which mainly filters out the 50Hz power frequency current of the line to avoid interference from the power frequency current.

[0059] High-speed ADCs primarily perform digital-to-analog conversion of high-frequency traveling wave currents;

[0060] The controller is mainly responsible for determining whether a fault has actually occurred in the line and driving the 4G communication module to transmit data.

[0061] The 4G communication module completes the remote transmission of fault data to the data center station.

[0062] The monitoring terminal controller samples data from the ADC, with a data length of N. Calculate the first-order difference value of this data.

[0063] Δx(n) = x(n+1) - x(n)

[0064] Calculate the average power from the first point to the Pth point in the difference value Δx(n) (the first average power P). a ):

[0065]

[0066] Calculate the average power (second average power P) from the (P+1)th point to the (P+Q)th point in the difference value Δx(n). b ):

[0067]

[0068] Calculate the average power ratio r at both ends:

[0069]

[0070] Fault current identification: if r < r_th, the current data is non-fault data; otherwise, the current data is fault data. Here, r_th is the threshold value for energy mutation.

[0071] Specifically, Figures 4 to 7 This diagram illustrates the analysis results of data under different conditions in this embodiment. The results are obtained by comparing the r value. Specifically: for fault current identification, if r < r_th, the current data is non-fault data; otherwise, the current data is fault data, where r_th = 1.5, the threshold value for energy mutation.

[0072] The beneficial effects of this invention are as follows:

[0073] This invention identifies fault current by whether the ratio of the second average power to the first average power changes abruptly, which can effectively avoid noise interference and improve the sensitivity of fault current identification.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0075] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for fault current identification in a distributed traveling wave ranging terminal of a distribution network, characterized in that, include: The traveling wave current data of the distribution network lines is collected using a pre-set distributed traveling wave ranging terminal for the distribution network. First-order differential calculation is performed on the traveling wave current data of the distribution network line to obtain a differential dataset; The average of the squares of the first P data points in the differential dataset is calculated to obtain the first average power; P is the number of data points before the traveling wave current data of the distribution network line is collected. The average of the squares of the (P+1)th to (P+Q)th data points in the differential dataset is calculated to obtain the second average power; Q is the number of data points after the traveling wave current data of the distribution network line is collected. Calculate the ratio of the second average power to the first average power to obtain the ratio to be judged; When the ratio to be judged is less than the mutation threshold, the traveling wave current data of the distribution network line is non-line fault data; When the ratio to be judged is greater than the mutation threshold, the traveling wave current data of the distribution network line is the traveling wave data of the line fault.

2. The method for fault current identification in a distributed traveling wave ranging terminal of a distribution network according to claim 1, characterized in that, The formula for calculating the difference dataset is: ;in, This refers to the nth data point in the differential dataset. This refers to the nth data point in the traveling wave current data of the distribution network line.

3. The method for fault current identification in a distributed traveling wave ranging terminal of a distribution network according to claim 1, characterized in that, The mutation threshold value is 1.

5.

4. The method for fault current identification in a distributed traveling wave ranging terminal of a distribution network according to claim 1, characterized in that, The traveling wave current data of the distribution network lines is collected using a pre-set ranging terminal, including: The target line is coupled using the Rogowski coil inside the ranging terminal to obtain the original analog current data; Integrating the original analog current data yields reconstructed analog current data; The reconstructed analog current data is high-pass filtered to obtain filtered analog current data; The analog current filtering data is converted from analog to digital to obtain the traveling wave current data of the distribution network line.

5. A distributed traveling wave ranging terminal for a distribution network applied to the fault current identification method according to any one of claims 1-4, characterized in that, include: The Rogowski coil, integrator circuit, filter circuit, high-speed ADC, controller, and 4G communication module are connected in sequence. The Rogowski coil is used to couple the target line to obtain the original analog current data; the integrator circuit is used to integrate the original analog current data to obtain the reconstructed analog current data; the filter circuit is used to perform high-pass filtering on the reconstructed analog current data to obtain the analog current filtered data; the high-speed ADC is used to perform analog-to-digital conversion on the analog current filtered data to obtain the traveling wave current data of the distribution network line. The controller is used to determine the fault status of the target line based on the traveling wave current data of the distribution network line, and obtain fault data; The 4G communication module is used to upload the fault data to a pre-set data center station.

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