Distribution network distributed traveling wave fault location terminal and fault current identification method

Abstract

The invention belongs to the field of power distribution network fault detection, and provides a power distribution network distributed traveling wave fault location terminal and a fault current identification method, and the method comprises the steps: power distribution network line traveling wave current data collection, first-order difference calculation, first average power calculation, second average power calculation, to-be-judged ratio calculation and operation state judgment. According to the invention, the fault current is identified according to whether the ratio of the second average power to the first average power changes suddenly, the interference of noise can be effectively avoided, and the sensitivity of fault current identification is improved.

Description

Technical Field

[0001] The present invention relates to the field of distribution network fault detection, and particularly to a distributed traveling wave ranging terminal for a distribution network and a fault current identification method. Background Art

[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 through a wireless network, and the data center station calculates the fault location using the double-end positioning principle for the uploaded traveling wave data with timestamps. Generally, the traveling wave sampling channels of monitoring terminal devices filter out the power frequency 50Hz component, and the traveling wave uses the threshold triggering principle. When the amplitude of the high-frequency traveling wave exceeds a certain threshold, the system is triggered to record the line current for a certain period of time.

[0003] However, when there are harmonics in the distribution network line or the terminal noise is large, the interfering noise and harmonics enter the traveling wave channel, which may cause the traveling wave amplitude to exceed the threshold, resulting in false triggering of the traveling wave. If the problem of false triggering is solved by increasing the threshold, some weak faults may not be triggered normally, increasing the probability of missed reports. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a distributed traveling wave ranging terminal for a distribution network and a fault current identification method, which identify the fault current by whether the ratio of the second average power to the first average power changes suddenly, avoiding the interference of noise and improving the sensitivity of fault current identification.

[0005] To achieve the above purpose, the present invention provides the following solutions:

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

[0007] Collecting traveling wave current data of a distribution network line by using a pre-set distributed traveling wave ranging terminal for a distribution network;

[0008] Performing a first-order difference calculation on the traveling wave current data of the distribution network line to obtain a difference data set;

[0009] Calculating the average value of the squares of the first P data in the difference data set to obtain a first average power; P is the number of data points before the collection of the traveling wave current data of the distribution network line;

[0010] Calculating the average value of the squares of the data from the (P + 1)-th to the (P + Q)-th in the difference data set to obtain a second average power; Q is the number of data points after the collection of the traveling wave current data of the distribution network line;

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

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

[0014] Preferably, the calculation formula of the differential data set is: Δx(n) = x(n + 1) - x(n); where, Δx(n) is the nth data in the differential data set; 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 by using a pre-set ranging terminal, including:

[0017] Coupling the target line by using the Rogowski coil in the ranging terminal to obtain original analog current data;

[0018] Integrating the original analog current data to obtain reconstructed analog current data;

[0019] Performing high-pass filtering on the reconstructed analog current data to obtain analog current filtered data;

[0020] Performing analog-to-digital conversion on the analog current filtered data to obtain the traveling wave current data of the distribution network line.

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

[0022] The Rogowski coil is used to couple the target line to obtain original analog current data; the integrating current is used to integrate the original analog current data to obtain reconstructed analog current data; the filter circuit is used to perform high-pass filtering on the reconstructed analog current data to obtain 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 judge the fault state of the target line according to 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] The present invention provides a distribution network distributed traveling wave ranging terminal and a fault current identification method, which identifies the fault current by whether the ratio of the second average power to the first average power changes suddenly, solves the defect that traditional fault current identification is prone to false triggering, and realizes reliable and sensitive identification of the fault current. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

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

[0027] Figure 2 It is a flowchart of the fault current identification provided by an embodiment of the present invention;

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

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

[0030] Figure 5 It is a schematic diagram of false triggering data caused by equipment noise provided by an embodiment of the present invention;

[0031] Figure 6 It is a schematic diagram of real fault data of metal grounding fault records provided by an embodiment of the present invention;

[0032] Figure 7 It is a schematic diagram of real fault data of tree fault records provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] The object of the present invention is to provide a distribution network distributed traveling wave ranging terminal and a fault current identification method, which identify the fault current by whether the ratio of the second average power to the first average power changes suddenly, avoid the interference of noise, and improve the sensitivity of fault current identification.

[0035] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0036] Figure 1 It is a schematic diagram of the fault current identification process provided by an embodiment of the present invention. Figure 2 It is a flow chart of the fault current identification provided by an embodiment of the present invention. As Figure 1 and Figure 2 shown, the present invention provides a method for identifying a fault current of a distribution network distributed traveling wave ranging terminal, including:

[0037] Step 100: Use a pre-set distribution network distributed traveling wave ranging terminal to collect traveling wave current data of a distribution network line;

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

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

[0040] Step 400: Calculate the average value of the squares of the data from the (P + 1)-th to the (P + Q)-th in the difference data set to obtain the second average power; Q is the number of data points after the collection of the traveling wave current data of the distribution network line;

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

[0042] Step 600: When the ratio to be judged is less than the mutation threshold value, 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 mutation threshold value, the traveling wave current data of the distribution network line is line fault traveling wave data.

[0044] Specifically, the calculation formula of the difference data set is: Δx(n) = x(n + 1) - x(n); where, Δx(n) is the n-th data in the difference data set; x(n) is the n-th data in the traveling wave current data of the distribution network line.

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

[0046] Specifically, a preset ranging terminal is used to collect traveling wave current data of the distribution network line, including:

[0047] The Rogowski coil in the ranging terminal is used to couple the target line to obtain the original analog current data;

[0048] The original analog current data is integrated to obtain the reconstructed analog current data;

[0049] The reconstructed analog current data is subjected to high-pass filtering to obtain the analog current filtered data;

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

[0051] Reference Figure 3 , a distributed traveling wave ranging terminal for a distribution network, including: a Rogowski coil, an integrating current, a filtering 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 traveling wave current data of the distribution network line; the controller is used to judge the fault state of the target line according to the traveling wave current data of the distribution network line to obtain the fault data; the 4G communication module is used to upload the fault data to a preset data center station.

[0053] Specifically, the distributed traveling wave ranging terminal for a distribution network collects the traveling wave current of the distribution network line in real time, where the traveling wave current refers to the high-frequency transient current filtered out of the power frequency of 50 Hz. When it is monitored that the traveling wave current meets the trigger condition, the traveling wave recording process will be triggered. Finally, the terminal will upload 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 is mainly composed of main components such as a Rogowski coil, an integrating current, a filtering circuit, a high-speed ADC, a controller, and a 4G communication module.

[0056] Among them, the Rogowski coil mainly realizes the coupling of the line current, and the basic principle is to integrate the line current and then convert it into a small current that can be collected and processed for the second time;

[0057] The integrating circuit realizes the integration of the secondary voltage of the Rogowski coil, thereby restoring the current characteristics of the line;

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

[0059] The high-speed ADC mainly realizes the analog-to-digital conversion of high-frequency traveling wave current;

[0060] The controller mainly judges whether a fault actually occurs in the line and drives the 4G communication module to perform data transmission;

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

[0062] The monitoring terminal controller calculates the first-order difference value of the data sampled by the ADC with a data length of N:

[0063] Δx(n) = x(n + 1) - x(n)

[0064] Calculate the average power from the 1st point to the Pth point in the difference value Δx(n) (the first average power P a ) :

[0065]

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

[0067]

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

[0069]

[0070] Fault current identification. If r < r_th, the current is non-fault data; otherwise, the current is fault data, where r_th is the threshold value of energy mutation.

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

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

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

[0074] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0075] In this article, specific examples are used to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A method for identifying fault current of a distributed traveling wave ranging terminal in a distribution network, characterized in that Including: Collecting traveling wave current data of the distribution network line by using a pre-set distributed traveling wave ranging terminal for the distribution network; Performing first-order difference calculation on the traveling wave current data of the distribution network line to obtain a difference data set; Calculating the average value of the squares of the first P data in the difference data set to obtain a first average power; P is the number of data points before the collection of the traveling wave current data of the distribution network line; Calculating the average value of the squares of the data from the (P + 1)-th to the (P + Q)-th in the difference data set to obtain a second average power; Q is the number of data points after the collection of the traveling wave current data of the distribution network line; Calculating the ratio of the second average power to the first average power to obtain a ratio to be judged; When the ratio to be judged is less than the mutation threshold value, 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 value, the traveling wave current data of the distribution network line is traveling wave data of line fault.

2. A fault current identification method for a distributed traveling wave ranging terminal in a distribution network according to claim 1, characterized in that The calculation formula of the difference data set is: Δx(n) = x(n + 1) - x(n); where, Δx(n) is the n-th data in the difference data set; x(n) is the n-th data in the traveling wave current data of the distribution network line.

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

5.

4. A fault current identification method for a distribution network distributed traveling wave ranging terminal according to claim 1, characterized in that Collecting traveling wave current data of the distribution network line by using a pre-set ranging terminal, including: Coupling the target line by using a Rogowski coil in the ranging terminal to obtain original analog current data; Integrating the original analog current data to obtain reconstructed analog current data; Performing high-pass filtering on the reconstructed analog current data to obtain analog current filtered data; Performing analog-to-digital conversion on the analog current filtered data to obtain the traveling wave current data of the distribution network line.

5. A distributed traveling wave ranging terminal for a distribution network, characterized in that, Including: A Rogowski coil, an integrating current, a filtering circuit, a high-speed ADC, a controller and a 4G communication module connected in sequence; The Rogowski coil is used to couple the target line to obtain original analog current data; the integrating current is used to integrate the original 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 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 judge the fault state of the target line according to 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.

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