Inspection Method and System for Low-Current Grounding Line Selection Device Based on Waveform Derivation

Abstract

This invention belongs to the field of device verification technology and provides a method and system for testing small current grounding fault location devices based on waveform propagation. The method includes: acquiring real fault voltage and current waveform data; propagating the acquired waveform data, selecting a portion of the waveform data based on a time scale for replication, adding the replicated portion of the waveform data to at least one preset position, and reducing or increasing the overall amplitude of the waveform data by a preset factor; and using the propagated waveform data to test the small current grounding fault location device. This invention uses real fault voltage and current waveform data from actual substations and propagates the waveform data to test the small current fault location device, thereby improving the testing accuracy of the small current fault location device while accurately reflecting the actual fault occurring on-site.

Description

Technical Field

[0001] This invention belongs to the field of device verification technology, and in particular relates to a method and system for testing a small current grounding line selection device based on waveform evolution. Background Technology

[0002] The power distribution network directly faces end users and is a crucial component of the power system. Distribution lines are characterized by numerous points of contact, long lengths, and wide coverage. Furthermore, the quality of connecting equipment varies, and the operating environment is highly variable, significantly affected by climate and geography. Due to urban and rural construction and development, power supply conditions are complex, making them highly susceptible to external interference and human sabotage. Consequently, the failure rate remains consistently high, constantly impacting the safe operation of distribution lines. Statistics show that over 85% of power outages are caused by distribution network faults, and single-phase grounding faults in the distribution network account for over 80% of all distribution network faults. Therefore, single-phase grounding fault detection in the distribution network is of paramount importance for the safe operation of the entire power system.

[0003] Currently, various low-current fault location devices and relay protection equipment are used in practical engineering applications to detect single-phase grounding faults in distribution networks. However, due to the uncertainty of single-phase grounding faults and the complexity of fault location issues, there are still significant differences between theoretical research and actual field conditions. Fault location devices or protection equipment that have passed laboratory testing still experience faulty fault location or failure to operate when a real single-phase grounding fault occurs in the field.

[0004] The inventors discovered that, currently, the most common field testing method for low-current grounding fault location devices is to directly apply parameters using a relay protection tester or a microcomputer protection tester. While this method is simple and easy to wire, it outputs a limited zero-sequence current, making it impossible to simultaneously compare and analyze multiple electrical quantities. Furthermore, applying parameters via a tester only tests the steady-state fault process of the device, resulting in incomplete testing and an inability to fully match the voltage and current changes during actual field faults. With the development and construction of hardware-in-the-loop (HIL) simulation platforms such as ADPSS, RTLAB, and RTDS, which allow for system modeling to control the output current and voltage of power amplifiers, this testing method is simple and convenient, enabling modeling and simulation of different systems. This method can simulate the transient process of a single-phase ground fault in a distribution network. However, it requires a large number of instruments, including multiple power amplifiers, servers, and UPS power supplies. In addition, since this test is still based on digital simulation, the voltage and current data obtained are theoretical values, which are quite different from the voltage and current generated by a fault in a real distribution network. Testing the small current ground fault location device in an outdoor full-scale test field is also one of the current verification methods. The advantage of this method is that it can accurately sample the voltage and current of a single-phase ground fault in the distribution network system. However, the system built by this test method is relatively simple. Due to the complexity of the power supply situation of the distribution network, it is difficult for an outdoor full-scale test field to simulate other complex distribution network conditions. At the same time, the construction cost of an outdoor full-scale test field is high. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a testing method and system for low-current grounding fault location devices based on waveform evolution. This invention utilizes a grounding fault database and an encryption device to realistically simulate the waveform of a single-phase grounding fault in a distribution network. Furthermore, it allows for the setting and modification of the fault waveform to a certain extent, greatly facilitating on-site testing of low-current grounding fault location devices.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for testing a small current grounding fault location device based on waveform evolution, comprising:

[0008] Obtain actual fault voltage and current waveform data;

[0009] The acquired waveform data is processed by selecting a portion of the waveform data based on the time scale, copying the copied portion of the waveform data, adding the copied portion of the waveform data to at least one preset position, and reducing or increasing the overall amplitude of the waveform data by a preset factor.

[0010] The low-current grounding fault location device is tested using the derived waveform data.

[0011] Furthermore, after acquiring the actual fault voltage and current waveform data, preliminary processing is performed to remove data within the first preset time period in the initial region of the waveform data, and data within the second preset time period in the end region of the waveform data.

[0012] Furthermore, waveform data propagation includes further expansion and propagation factor settings; further expansion involves adding waveform data of a preset length, selecting a portion of the waveform data from the initially processed waveform data for copying, setting the time scale of the copied waveform data to an integer multiple of the waveform period, adding the copied waveform data at the final moment of the original copied waveform, and adding multiple copied waveform data; the propagation factor setting involves reducing or increasing the overall amplitude of the waveform data by a preset factor.

[0013] Furthermore, multiple fault waveforms are derived.

[0014] Furthermore, transient and steady-state fault signals are generated based on the actual fault voltage and current waveform data to verify the low-current ground fault location device, and to determine whether the low-current ground fault location device will produce false alarms and / or no action after the fault line has been running for a preset time.

[0015] Furthermore, real fault voltage and current waveform data are obtained from a preset database, and the database startup, usage, and modification settings are each encrypted separately.

[0016] Secondly, the present invention also provides a small current grounding fault location device inspection system based on waveform evolution, including a control storage module, and a voltage power amplifier, a current power amplifier, and a database connected to the control storage module by the user; a software lock is provided between the control storage module and the database;

[0017] A voltage power amplifier is configured to provide voltage for a low-current grounding selector.

[0018] A current power amplifier is configured to provide current to a low-current grounding selector.

[0019] The database is configured to: store real fault voltage and current waveform data; reproduce the waveform data, select a portion of the waveform data based on the time scale for copying, add the copied portion of the waveform data to at least one preset position, and reduce or increase the overall amplitude of the waveform data by a preset factor.

[0020] Thirdly, the present invention also provides a small current grounding fault location testing system based on waveform evolution, comprising:

[0021] The data acquisition module is configured to acquire real fault voltage and current waveform data.

[0022] The data propagation module is configured to: propagate the acquired waveform data, select a portion of the waveform data based on the time scale for copying, add the copied portion of the waveform data to at least one preset position, and reduce or increase the overall amplitude of the waveform data by a preset factor.

[0023] The testing module is configured to test the low-current grounding fault location device using the derived waveform data.

[0024] Fourthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the waveform-derived small current grounding fault location test method described in the first aspect.

[0025] Fifthly, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the waveform-derived small current grounding line selection device inspection method described in the first aspect.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. In this invention, the actual fault voltage and current waveform data of the actual substation are used to test the low current fault location device after the waveform data is derived. Based on the actual fault that occurs on site, the test accuracy of the low current fault location device is improved.

[0028] 2. The database proposed in this invention requires separate encryption devices for its startup, use and modification, which can prevent the original waveform data from being tampered with, ensure the security and stability of the data, and at the same time solve the problem of data file sharing, providing convenient conditions for the work of selecting grounding lines with low current.

[0029] 3. This invention proposes a low-current ground fault location device inspection system based on waveform evolution. It can generate transient and steady-state fault signals through an internal programmable power supply based on the actual fault voltage and current waveform data of the actual substation, which are used to verify the low-current ground fault location device. It can output voltage and current quantities that can vary according to a certain multiple. This function can check the voltage and current judgment threshold of the low-current ground fault location device, and at the same time, it can spread the stable fault state of the original voltage and current to observe whether the low-current ground fault location device will have false alarms or no action after the fault line has been running for a period of time.

[0030] 4. The fault waveform propagation single-phase grounding signal generator proposed in this invention can verify the accuracy of the low-current grounding line selection device; by setting a certain operating state, operating time and fault mode, as well as parameters such as the number of grounding verifications and fault verification intervals, the fault waveform propagation single-phase grounding signal generator can directly statistically analyze the line selection of the low-current connection line selection device, including relevant information on the accuracy of multiple tests of the line selection device.

[0031] 5. The small current grounding fault location device testing system proposed in this invention has the characteristics of integration, simple structure, easy portability and simple operation, which is convenient for field practice. Attached Figure Description

[0032] The accompanying drawings, which form part of this embodiment, are used to provide a further understanding of this embodiment. The illustrative embodiments and their descriptions are used to explain this embodiment and do not constitute an improper limitation of this embodiment.

[0033] Figure 1 This is a flowchart of Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the preliminary waveform data processing in Embodiment 1 of the present invention;

[0035] Figure 3 This is a schematic diagram of waveform data propagation in Embodiment 1 of the present invention;

[0036] Figure 4 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0037] Figure 5 This is a schematic diagram of the interface in Embodiment 2 of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] 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.

[0040] The low-current fault location device, also known as a low-current ground fault location device or simply low-current, is a protective device used in the power industry. This device is suitable for single-phase ground fault location in 3kV-66kV systems with ungrounded neutral points or neutral points grounded via resistors and arc suppression coils. It is used in power systems of substations, power plants, hydropower stations, and large-scale factories and mines in industries such as chemical, oil, metallurgy, coal, and railways. It can indicate the line where a single-phase ground fault has occurred. Low-current ground fault location, also called low-current ground fault protection, selects the line with the ground fault and provides an indication signal.

[0041] Example 1:

[0042] like Figure 1 As shown, this embodiment provides a testing method for a small current grounding fault location device based on waveform evolution, including:

[0043] Obtain actual fault voltage and current waveform data;

[0044] The acquired waveform data is processed by selecting a portion of the waveform data based on the time scale, copying the copied portion of the waveform data, adding the copied portion of the waveform data to at least one preset position, and reducing or increasing the overall amplitude of the waveform data by a preset factor.

[0045] The low-current grounding fault location device is tested using the derived waveform data.

[0046] In this embodiment, the process of implementing the small current grounding fault location device inspection method based on waveform propagation is mainly achieved through six functional modules, including fault waveform selection and preliminary processing, waveform propagation setting, simultaneous setting of multiple fault waveform verification, setting of test interval sequence and number of tests, setting of communication connection between the device and the device under test, and detection start-up and result output.

[0047] Fault waveform selection and preliminary handling, such as Figure 2 As shown, this module is used for selecting the original fault waveform to be output and for preliminary waveform processing. After acquiring the actual fault voltage and current waveform data, it performs preliminary processing, removing data within a first preset time period in the initial region of the waveform data, and removing data within a second preset time period in the end region of the waveform data. The first preset time period can be understood as... Figure 2 In the time interval 0 to t1, the second preset time can be understood as... Figure 2The time period t2 to t3 is used. The selection of original fault waveform data can be achieved by accessing the ground fault waveform database via software connection, inputting other fault waveforms via USB interface, or using waveforms stored internally by the single-phase grounding signal generator. Waveform data processing involves removing unusable or useless portions of the original fault waveform, retaining only useful data. Unusable waveform portions are mainly concentrated in the initial and final regions of the waveform; if there are no useless portions, this operation can be omitted. This waveform processing can be done graphically, directly modifying the waveform using a ruler corresponding to the time scale, or by setting the time period of the original fault waveform to be processed.

[0048] Waveform propagation settings, such as Figure 3 As shown, the waveform propagation function propagates the previously processed fault waveform data. The main propagation settings include further expansion of the waveform file and preset multiple changes in waveform amplitude. For waveform file expansion, considering the short duration of typical fault recordings, making it difficult to observe the operation and display of the device under test for extended periods, a certain length of waveform data is manually added in the background. This is done by selecting and copying the portion of the fault waveform to be propagated from the initially processed waveform. The time scale for copying the waveform to be propagated is generally set to an integer multiple of the waveform period (tn-tm). The position where the waveform to be propagated is added is the final moment (tn) of the original copied waveform. Multiple (k) waveforms to be propagated can be added, with the original and subsequent waveforms sequentially delayed. This function allows for multiple expansion settings for the same waveform. The waveform data propagation multiple is set to reduce or increase the overall amplitude of the waveform by a certain multiple, meeting the range requirements. Waveform processing can also be performed graphically, directly modifying the waveform using a scale corresponding to the time scale, or by setting the time period of the original fault waveform to be processed.

[0049] This function allows for the simultaneous setting of multiple fault waveform verifications. It enables waveform propagation settings and other processing for multiple fault waveforms, and simultaneously performs output verification.

[0050] The function of setting the test interval sequence and number of tests determines the number of faults, the frequency of occurrence, and the test sequence for various waveform tests, as well as setting the test interval time. This function is mainly used by buyers, manufacturers, or laboratories to verify the accuracy of the low-current grounding fault location device; in addition, substations can use it for various functional verifications or technical supervision of the low-current grounding fault location device.

[0051] The communication connection settings between the device and the device under test are configured to enable communication between the single-phase grounding signal generator and the low-current grounding line selection device, and to analyze and statistically analyze the feedback from the low-current grounding line selection device.

[0052] The test starts and outputs results. This setting is used for testing, and the human-machine interface can display relevant parameters. The test can be stopped midway.

[0053] In this embodiment, transient and steady-state fault signals are generated based on real fault voltage and current waveform data to verify the low-current grounding fault location device. It can perform waveform data propagation and expansion settings to amplify the stable fault state of the original voltage and current, allowing observation of whether the low-current fault location device will experience false alarms and / or inaction after operating on the faulty line for a period of time. It can also set the waveform data propagation multiple, processing the obtained fault voltage and current data internally and outputting voltage and current quantities that can vary according to a certain multiple. This function can verify the voltage and current judgment threshold of the low-current grounding fault location device. This embodiment also proposes a fault waveform storage database to store and record real grounding fault waveform data from the substation. The database startup, use, and modification require separate encryption devices, such as a dongle for verification, to prevent tampering of the original waveform data, ensuring data security and stability. It also solves the problem of data file sharing, providing convenient conditions for low-current grounding fault location operations.

[0054] This embodiment can perform technical supervision and functional verification of the low-current grounding line selection device, and can also carry out line selection accuracy verification of the low-current grounding line selection device. By setting a certain operating state, operating time and fault mode, as well as parameters such as the number of grounding verifications and fault verification intervals, the fault waveform can generate a single-phase grounding signal that can directly statistically analyze the line selection of the low-current grounding line selection device, including relevant information on the accuracy of multiple tests of the line selection device.

[0055] Example 2:

[0056] To implement the method in Embodiment 1, this embodiment provides a small current grounding fault location testing system based on waveform evolution, such as... Figure 4 As shown, it includes a control storage module, as well as a user interface, a voltage power amplifier, a current power amplifier, a software lock, and a line grounding fault waveform database connected to the controller;

[0057] The control storage module is the core of the device's computing and storage, including a processor and a memory. The processor can be composed of a DSP chip and an FPGA chip, mainly for the convenience of signal processing and computation. The memory configuration needs to match the processor's computing speed, and at the same time, it is required to store enough waveform data.

[0058] The user interface serves as the medium for interaction and information exchange between the device and the user. Users can perform relevant configuration functions through the interface, including device operating status, waveform display, waveform generation, data storage, function selection, and voltage and current settings.

[0059] The voltage power amplifier is used for voltage output; it is required to include at least one three-phase voltage output and one zero-sequence voltage output, with a single-phase steady-state output voltage range of 0 to 100V and a maximum steady-state voltage not exceeding 100V. It can output higher voltages for short periods of time; it must meet requirements such as good linearity, fast response, high precision, good electromagnetic compatibility, and phase accuracy, with linearity reaching less than 0.1%.

[0060] The current power amplifier is used for current output; it is required to include at least 5 zero-sequence current outputs, with a single-phase steady-state output current range of 0-5A, and the ability to output high current for short periods. It must meet requirements such as good linearity, fast response, high accuracy, good electromagnetic compatibility, no DC bias, and phase accuracy, with an accuracy of 0.02% error, reaching the 1mA level.

[0061] The software lock is responsible for communication and connection between the single-phase grounding signal generator and the grounding fault waveform database. Access to the grounding fault waveform database is granted through the software lock. At the same time, the single-phase grounding signal generator is authorized to collect and use some waveform data in the database. Without the software lock, access to the grounding fault waveform database is impossible.

[0062] The ground fault waveform database can be implemented using technologies such as cloud storage. This database stores single-phase ground fault waveforms generated in real environments, and can store waveforms in formats such as comtrade, csv, and binary files.

[0063] In this embodiment, the interface structure is as follows: Figure 5 As shown, it includes three-phase voltage output, zero-sequence voltage output, multiple zero-sequence current outputs, multiple signal terminal inputs, software encryption port, debugging network port, and USB input / output, etc.

[0064] The three-phase voltage output, including the neutral point, provides a three-phase voltage output port for the low-current grounding fault location device. The single-phase voltage value corresponds to the secondary voltage of the voltage transformer, and the single-phase output voltage range is 0 to 100V, with a maximum steady-state voltage not exceeding 100V.

[0065] The zero-sequence voltage output includes a zero-sequence voltage circuit, providing an output port for the zero-sequence voltage of the low-current grounding fault location device. The zero-sequence voltage value corresponds to the voltage of the secondary auxiliary winding of the voltage transformer, and the zero-sequence voltage output range is 0 to 100V, with a maximum steady-state voltage not exceeding 100V.

[0066] The multiple zero-sequence current outputs include a zero-sequence current loop, providing zero-sequence current output ports for low-current ground fault location devices. Considering that the ground fault judgment criteria of some low-current ground fault location devices are related to the number of outgoing lines, at least 5 pairs of zero-sequence current output ports are provided. The zero-sequence current value corresponds to the secondary current of the zero-sequence current transformer, and the zero-sequence current output range is 0 to 5A, with the maximum current not exceeding 5A.

[0067] The multiple signal terminal inputs are terminals that receive busbar and outgoing line trip signals from the low-current ground fault location device. Considering that the ground fault judgment criteria of some low-current ground fault location devices are related to the number of outgoing lines, at least 6 signal terminal inputs are provided, including 1 busbar trip signal port and 5 branch trip signal ports.

[0068] The software encryption port is used for the installation of the dongle. The dongle is used to control and process relevant grounding waveform data.

[0069] The debugging network port is connected and used for updating the internal software and system of the single-phase grounding signal generator.

[0070] The USB input / output connects to an external USB device. It is used to output relevant test waveform data and accuracy reports from the device, and can also read fault waveform data from the USB.

[0071] This embodiment proposes a fault waveform storage database for storing and recording real ground fault waveform data from substations. This includes waveform information, file format, date and time, location, substation name, substation voltage level, busbar number, branch number, system type, and subsequent ground fault analysis, such as analysis of grounding conditions and grounding resistance. The database can also be searched and categorized based on any of the above descriptions or categories. It can store various waveform formats, such as Comtrade, CSV, and binary files.

[0072] The device in this embodiment can communicate with the low-current grounding line selection device to verify the line selection results, collect data, and ultimately generate a report directly, which greatly simplifies the work. The device in this embodiment is integrated, simple in structure, easy to carry, and easy to operate.

[0073] The working method of the system is the same as the test method of the small current grounding line selection device based on waveform evolution in Embodiment 1, and will not be repeated here.

[0074] Example 3:

[0075] This embodiment provides a small-current grounding fault location testing system based on waveform evolution, including:

[0076] The data acquisition module is configured to acquire real fault voltage and current waveform data.

[0077] The data propagation module is configured to: propagate the acquired waveform data, select a portion of the waveform data based on the time scale for copying, add the copied portion of the waveform data to at least one preset position, and reduce or increase the overall amplitude of the waveform data by a preset factor.

[0078] The testing module is configured to test the low-current grounding fault location device using the derived waveform data.

[0079] The working method of the system is the same as the test method of the small current grounding line selection device based on waveform evolution in Embodiment 1, and will not be repeated here.

[0080] Example 4:

[0081] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the small current grounding line selection device inspection method based on waveform derivation described in Embodiment 1.

[0082] Example 5:

[0083] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps of the small current grounding line selection device inspection method based on waveform evolution described in Embodiment 1.

[0084] The above description is merely a preferred embodiment of this practice and is not intended to limit the scope of this practice. Various modifications and variations can be made to this practice by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this practice should be included within the protection scope of this practice.

Claims

1. A testing method for low-current grounding fault location devices based on waveform evolution, characterized in that, include: Acquire real fault voltage and current waveform data. After acquiring the real fault voltage and current waveform data, perform preliminary processing to remove data within the first preset time period in the initial region of the waveform data and data within the second preset time period in the end region of the waveform data. The system retrieves real fault voltage and current waveform data from a pre-defined database, and encrypts the database separately for startup, use, and modification. The acquired waveform data is processed by selecting a portion of the waveform data based on the time scale and copying it. The copied portion of the waveform data is added to at least one preset position. The overall amplitude of the waveform data is reduced or amplified by a preset factor. Transient and steady-state fault signals are generated based on the actual fault voltage and current waveform data. The low-current grounding fault location device is tested using the derived waveform data. Waveform data propagation includes further expansion and propagation factor settings; Further, it can be expanded to include adding waveform data of a preset length, selecting a portion of the waveform data from the initially processed waveform data for copying, setting the time scale of the copied waveform data to an integer multiple of the waveform period, adding the copied waveform data at the final moment of the original copied waveform, and adding multiple copied waveform data; the propagation factor is set to reduce or increase the overall amplitude of the waveform data by a preset factor.

2. The testing method for a small current grounding fault location device based on waveform evolution as described in claim 1, characterized in that, Multiple fault waveforms are derived.

3. The testing method for a small current grounding fault location device based on waveform evolution as described in claim 1, characterized in that, The transient and steady-state fault signals generated based on the actual fault voltage and current waveform data are used to verify the low-current grounding fault location device, and to determine whether the low-current fault location device will produce false alarms and / or no action after the fault line has been running for a preset time.

4. A testing system for small-current grounding fault location devices based on waveform evolution, employing the testing method for small-current grounding fault location devices based on waveform evolution as described in any one of claims 1-3, characterized in that, It includes a control storage module, and a voltage power amplifier, a current power amplifier, and a database connected to the control storage module; a software lock is provided between the control storage module and the database; A voltage power amplifier is configured to provide voltage for a low-current grounding selector. A current power amplifier is configured to provide current to a low-current grounding selector. The database is configured to store real fault voltage and current waveform data. The waveform data is reproduced by selecting a portion of the waveform data based on the time scale, copying the copied portion of the waveform data, adding the copied portion of the waveform data to at least one preset position, and reducing or increasing the overall amplitude of the waveform data by a preset factor.

5. A testing system for small-current grounding fault location devices based on waveform evolution, employing the testing method for small-current grounding fault location devices based on waveform evolution as described in any one of claims 1-3, characterized in that, include: The data acquisition module is configured to acquire real fault voltage and current waveform data. The data propagation module is configured to: propagate the acquired waveform data, select a portion of the waveform data based on the time scale for copying, add the copied portion of the waveform data to at least one preset position, and reduce or increase the overall amplitude of the waveform data by a preset factor. The testing module is configured to test the low-current grounding fault location device using the derived waveform data.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the small current grounding line selection device inspection method based on waveform propagation as described in any one of claims 1-3.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the small current grounding line selection device inspection method based on waveform propagation as described in any one of claims 1-3.

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