A power distribution terminal single-phase ground fault research and judgment capability test method and system based on a real-type test platform

Abstract

The application provides a kind of distribution terminal single-phase ground fault research and judgment capability test method and system based on true type test platform, builds encrypted wireless communication environment and terminal hardware detection system, constructs the true type test field of adjustable network frame and grounding mode and selects overhead-cable hybrid test line;In the middle section, end and overhead-cable transition node of line, set up collaborative fault point, trigger multiple types of single-phase ground fault through fault simulation device, after collecting terminal response data, by master station according to the quantitative evaluation of differentiated scoring and multidimensional ranking rule realizes the quantitative evaluation of research and judgment capability.The application also constructs the test system containing six functional units, realizes the systematic and standardized test of distribution terminal single-phase ground fault research and judgment performance under highly realistic environment, solves the problems that traditional test and field working condition are disconnected, single in assessment dimension and lack of objectivity in evaluation, provides reliable basis for equipment selection, algorithm optimization and distribution network fault handling capability improvement.

Description

Technical Field

[0001] This invention relates to the field of power distribution automation technology, and in particular to a test method and system for assessing the ability to detect single-phase grounding faults in power distribution terminals based on a full-scale test platform. Background Technology

[0002] Single-phase grounding faults are the most common type of fault in distribution networks, and their accurate and rapid diagnosis and isolation are crucial for improving power supply reliability. Currently, the testing of the ability of distribution terminals (such as FTUs) to diagnose single-phase grounding faults is mostly conducted in simplified laboratories or through simulations, which has many technical shortcomings: First, the test environment cannot reproduce the complex power grid structure on site, especially the impedance discontinuity characteristics of overhead-cable hybrid lines, making it difficult to simulate the reflection and distortion of fault traveling waves; second, harmonic interference and load simulation use ideal signals, which deviate significantly from the harmonic characteristics and interference paths measured on site, making it impossible to truly assess the terminal's anti-interference capability; third, the fault point setting is too simplistic, and the assessment of fault selection in heavy fault areas, the ability to avoid false alarms in light fault areas, and the ability to select segments in impedance discontinuity scenarios are not comprehensive; fourth, there is a lack of standardized quantitative evaluation systems, with a high proportion of subjective judgment, making it impossible to achieve accurate horizontal comparison of equipment performance; fifth, the communication environment is simply set up, without considering the encryption and stability requirements of on-site data transmission, resulting in a disconnect between the test scenario and actual application.

[0003] The aforementioned issues lead to significant discrepancies between laboratory test results and actual field performance, making it impossible to comprehensively and accurately assess the equipment's line selection, segment selection performance, and anti-interference capabilities in complex scenarios. Therefore, there is an urgent need for a system and methodology capable of systematically and standardizedly testing distribution terminals in a test field that highly simulates a real power grid environment, in order to objectively evaluate their performance and guide product improvement and field applications. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method and system for testing the ability to identify single-phase grounding faults in distribution terminals based on a real-world test platform, and to provide a method and system for systematically testing and quantitatively evaluating the ability to identify single-phase grounding faults in distribution terminals in a highly realistic complex power grid environment.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a test method for single-phase grounding fault judgment capability of distribution terminals based on a full-scale test platform, comprising the following steps: S1: Based on the real-world test site and the power distribution master station, an encrypted wireless communication environment is built to perform wiring, insulation, continuity and grounding tests on the power distribution terminal and related test equipment; S2: Construct a realistic test field with diverse grid structures and adjustable neutral grounding methods, and select an overhead-cable hybrid test line as the test line; S3: Connect to typical harmonic interference sources and simulated loads based on field measured data. Simulate the actual power grid electromagnetic environment by using dual-position access at the bus side and upstream of the fault point, and dual-mode coupling of current injection and voltage superposition. S4: Set up coordinated fault points in the middle section, end and overhead-cable transition nodes of the test line, and trigger single-phase grounding faults covering different neutral grounding methods, grounding medium types and 750-4000Ω continuously adjustable transition resistance through the fault simulation device. S5: Collect the response data and alarm signals of the tested power distribution terminal after each fault and upload them to the power distribution master station; S6: The power distribution master station quantifies and ranks the single-phase grounding fault line selection and segment selection capabilities of the tested terminals according to the preset scoring and ranking rules. In step S1, a wireless communication module is added to the front-end server and an IoT card with a fixed IP is activated. Encrypted data transmission between the terminal and the front-end encryption machine is achieved through a dedicated VPN. In step S6, the scoring rules distinguish between line selection and segment selection assessment dimensions. When the total scores are the same, the ranking rules select the best candidate based on the number of false alarms and the number of missed alarms.

[0006] In a preferred embodiment, the overhead-cable hybrid test line in step S2 is a combination of a 13kM 10kV overhead test line II and a 10kV cable test line III, simulating the reflection and refraction of fault traveling waves at the impedance discontinuity interface, the sudden change in wave impedance, and the traveling wave distortion phenomenon.

[0007] In a preferred embodiment, the typical harmonic interference source in step S3 is a programmable harmonic source based on 72 hours of measured data from a textile factory in Fujian Province. The average total harmonic distortion rate of this scenario is 8.2%, and it is rich in 5th, 7th, and 11th harmonics, achieving a 1:1 true playback of harmonic waveforms.

[0008] In a preferred embodiment, the collaborative fault points mentioned in step S4 include the middle section F1, the end section F7, and the overhead-cable transition node F6 within the test line. F1 and F7 are used to assess the accuracy of fault line selection within the test area, F6 is used to assess the segment selection capability under impedance discontinuity scenarios, and the non-faulty line on the same bus is used to assess the ability to prevent false alarms of faults outside the test area.

[0009] In a preferred embodiment, the neutral point grounding method in step S4 includes an ungrounded method and a grounding method via an arc suppression coil. The grounding medium type includes sand and gravel medium, tree branch medium, and arc grounding. The arc grounding is an intermittent, short-time arc type.

[0010] In a preferred embodiment, the criterion for determining correctness in step S6 is: the terminal in the upstream section of the fault point reliably generates and sends a small current grounding alarm signal, while the terminal in the downstream section of the fault point does not generate a small current grounding alarm signal.

[0011] In a preferred embodiment, the scoring principle in step S6 is as follows: 0.5 points are awarded for correctly identifying a single fault point F1 or F7, and 1 point is awarded for both being correctly identified; 1 point is awarded for fault point F6 if both tested terminals are correctly identified.

[0012] This invention also provides a testing system for single-phase grounding fault assessment capability of distribution terminals based on a full-scale test platform. This system is used to implement the aforementioned testing method for single-phase grounding fault assessment capability of distribution terminals based on a full-scale test platform. It includes a full-scale test unit, a communication network unit, an environmental simulation unit, a fault triggering unit, a data acquisition unit, and a quantitative evaluation unit. The full-scale test unit is a medium- and low-voltage integrated full-scale verification platform, containing a multi-network structure with adjustable neutral grounding and a 13km overhead-cable hybrid test line, and is equipped with F1, F6, and F7 collaborative fault points. The communication network unit includes a distribution master station, a front-end server, a wireless communication module, an IoT card, and a front-end encryption machine, implemented via a dedicated VPN. Encrypted wireless data transmission between the distribution terminal and the main station; the environment simulation unit includes a programmable harmonic source and a simulated load device. The harmonic source is configured based on actual measured data from a textile factory and uses dual-position access and dual-mode coupling to simulate a complex electromagnetic environment; the fault triggering unit is a single-phase grounding fault simulation device that can trigger single-phase grounding faults with different neutral point grounding methods, grounding medium types, and adjustable transition resistances of 750-4000Ω; the data acquisition unit is the distribution terminal under test (FTU), used to collect fault response data and upload alarm signals to the distribution main station; the quantitative evaluation unit is the evaluation module of the distribution main station, with built-in preset scoring and ranking rules to achieve quantitative scoring and ranking of the terminal's line selection and segment selection capabilities.

[0013] In a preferred embodiment, the programmable harmonic source can realize 1:1 on-site waveform playback of total harmonic distortion rate and odd / even harmonic spectrum distribution, and the simulated load device can simulate the load current fluctuation characteristics of the actual power grid.

[0014] In a preferred embodiment, the power distribution master station has functions for power distribution network data acquisition and monitoring, fault data storage, quantitative evaluation of analysis capabilities and result display, so as to realize full traceability and analysis of test data.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. Highly realistic test environment with seamless integration with on-site conditions: A full-scale integrated low- and medium-voltage test field is built, and an overhead-cable hybrid test line is selected to realistically simulate the reflection and distortion phenomena of fault traveling waves; a programmable harmonic source is configured based on 72 hours of on-site measured data, and harmonic interference is reproduced using dual-position access and dual-mode coupling, combined with simulated load to achieve dual simulation of electromagnetic and load conditions; at the same time, an encrypted wireless communication environment is built to simulate the security and stability requirements of on-site data transmission, solving the core problem of the disconnect between traditional testing and on-site conditions, and making the test results more valuable for engineering reference.

[0016] 2. Comprehensive innovation in assessment dimensions, filling multiple technical gaps: Through the coordinated layout of three fault points (F1, F6, and F7), the system simultaneously assesses the accuracy of fault line selection within the terminal area, the ability to avoid false alarms for faults outside the area, and the segment selection capability under impedance discontinuity scenarios. For the first time, "fault judgment and segment selection capability" is included in the core assessment indicators, which is in line with the development direction of distribution network automation technology. The test items cover different neutral grounding methods, various grounding media, and 750-4000Ω continuously adjustable transition resistance. The test cases are complete and can fully expose the performance boundaries of the equipment under different fault characteristics.

[0017] 3. Objective and quantitative evaluation system to achieve accurate equipment comparison: Establish differentiated scoring principles, distinguish between line selection and segment selection assessment dimensions, and adapt to the test objectives of different fault points; establish multi-dimensional ranking rules, taking into account the number of false alarms and missed alarms in turn on the basis of total score, transforming subjective performance judgment into objective quantitative scores and rankings, providing a clear and fair basis for horizontal comparison of equipment performance and access selection, and solving the problem of strong subjectivity in traditional test evaluation.

[0018] 4. Modular system architecture with strong adaptability and scalability: The test system is divided into six functional units, each of which works independently yet collaboratively. The modular architecture allows the system to flexibly adjust parameters such as fault type, harmonic scenarios, and grid structure according to test requirements, adapting to the test needs of different regions and different types of distribution networks. At the same time, newly added test functions can be easily integrated into the corresponding units, providing excellent scalability.

[0019] 5. Test results can be directly implemented to promote the overall improvement of distribution network capabilities: By conducting full-process technical verification of terminal single-phase grounding fault judgment capabilities, the test experience can directly provide practical basis for large-scale promotion throughout the province; the fault data and terminal performance data accumulated during the test can promote the standardization of equipment parameters and the expansion of master station algorithm functions, thereby improving the overall fault handling capability of the distribution network and realizing the seamless transformation of test results to field applications. Attached Figure Description

[0020] Appendix Figure 1This is a flowchart of a test system and method for assessing single-phase grounding faults in power distribution terminals based on a real-world test platform, according to the present invention. Appendix Figure 2 This is the experimental project of the present invention; Appendix Figure 3 This is a simplified diagram of the experimental grid structure of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] It should be noted that the following detailed descriptions are illustrative 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.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations 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.

[0024] like Figure 1 As shown, a full-process test system and method for centralized analysis of single-phase grounding faults based on real-world tests in distribution substation transient recording includes the following steps; S1: Based on the real-world test site and the power distribution master station, an encrypted wireless communication environment is built to perform wiring, insulation, continuity and grounding tests on the power distribution terminal and related test equipment; S2: Construct a realistic test field with diverse grid structures and adjustable neutral grounding methods, and select an overhead-cable hybrid line as the test line; S3: Connect to typical harmonic interference sources and simulated loads based on field measured data. Simulate the actual power grid electromagnetic environment by using dual-position access on the bus side and upstream of the fault point, and dual-mode coupling of current injection and voltage superposition. S4: Set up coordinated fault points in the middle section, end and overhead-cable transition nodes of the test line, and trigger single-phase grounding faults covering different neutral grounding methods, grounding medium types and 750-4000Ω continuously adjustable transition resistance through the fault simulation device. S5: Collect the response data and alarm signals of the tested power distribution terminal after each fault and upload them to the power distribution master station; S6: The power distribution master station quantifies and ranks the single-phase grounding fault selection and segment judgment capabilities of the tested terminals according to the preset scoring and ranking rules.

[0025] Furthermore, in step S1, when setting up the encrypted wireless communication environment, since the front-end server is not connected to a telecommunications operator, a wireless communication module is added in front of the front-end server, and a fixed IP IoT card is activated. A dedicated VPN is used to achieve encrypted data transmission between the terminal and the front-end encryption machine, simulating a real and secure wireless communication method for power distribution terminals on-site. The test system includes a power distribution master station, a front-end server, and power distribution terminals. The master station and the front-end server are connected via a network cable, and the power distribution terminals and the front-end server are connected via the aforementioned encrypted wireless method. During the testing of the test equipment, the integrated primary and secondary pole-mounted circuit breakers are sequentially wired and placed in a real-world field to verify insulation performance, test circuit continuity, and terminal contact quality. Simultaneously, the terminal grounding is checked to ensure the basic condition of the test equipment meets the standards.

[0026] Furthermore, in step S2, the simulated test field is a low- and medium-voltage integrated simulated demonstration platform capable of simulating various typical single-phase grounding faults in distribution networks. Its network structure is diverse, and the neutral grounding method can be flexibly adjusted to adapt to different distribution network conditions. Considering the widespread use of a mixed overhead and cable power supply mode in urban and suburban distribution networks, a 13km overhead-cable hybrid test line formed by combining a 10kV overhead test line II and a 10kV cable test line III is selected as the test line. This line can realistically simulate the reflection, impedance abrupt change, and traveling wave distortion phenomena of fault traveling waves at the overhead-cable impedance discontinuity interface, avoiding test result deviations caused by a single line type. Simultaneously, the fault mechanisms and transient waveform characteristics of overhead lines and cable lines are fundamentally different. The hybrid line layout can simultaneously simulate typical faults in both types of sections in the same test cycle, improving test efficiency and scene coverage density.

[0027] Furthermore, in step S3, the most representative harmonic pollution scenarios were selected based on on-site measured data: continuous 72-hour power quality monitoring was conducted on four typical harmonic sources in Fujian Province: steel smelting, distributed photovoltaics, textile factories, and residential areas. The total harmonic distortion (THD), odd / even harmonic spectrum distribution, and 95% probability maximum values ​​were statistically analyzed for each scenario. The textile factory scenario was ultimately selected as the standard harmonic interference template. This scenario has an average THD of 8.2% and is rich in 5th, 7th, and 11th harmonics, having the most significant impact on zero-sequence voltage and current waveform distortion. The measured harmonic data from this scenario was then played back into a programmable harmonic source to achieve a 1:1 true reproduction of the harmonic waveform, avoiding test distortion caused by using ideal step or sinusoidal superposition signals.

[0028] To address the issues of spatial separation between harmonic sources and fault points, and mismatched interference paths in traditional testing, harmonic interference sources are simultaneously connected to both the bus side of the test line and the upstream section of the fault point. This creates a "fault point—harmonic source—measurement point" interference along the same electrical path, realistically simulating harmonic pollution from distributed power grid connection points and nonlinear load feeders during the transient process of grounding faults. Furthermore, a dual-mode coupling method combining current injection and voltage superposition is employed to ensure the physical realism of both high-order harmonic conduction and zero-sequence loop interference, maximizing the replication of the complex electromagnetic environment on-site. The simulated load device is configured according to the characteristics of the on-site distribution network load, simulating load current fluctuations in the actual power grid, achieving dual simulation of the electromagnetic environment and load conditions.

[0029] Furthermore, in step S4, the neutral point grounding method includes ungrounded mode and grounding mode via arc suppression coil, covering the mainstream grounding mode of distribution network; the grounding medium type includes sand and gravel medium, tree branch medium and arc grounding, wherein the arc grounding is intermittent and short-time arc type, which conforms to the medium characteristics of actual grounding faults on site; the transition resistance value is continuously adjustable in the range of 750 ohms to 4000 ohms, which can test the judgment performance boundary of the terminal under different non-metallic grounding faults.

[0030] The fault point adopts a "coordinated layout" strategy of three fault points: F1 (middle section of the line) and F7 (end of the line), both located within the test line, are used to assess the accuracy of fault location within the terminal area. No fault point is set on the non-faulty line on the same busbar, used to assess the ability to prevent false alarms outside the terminal area. Both are tested simultaneously to avoid the false alarm rate omissions caused by prioritizing faults within the terminal area over those outside. F6 is located near the overhead-cable transition node, effectively assessing the sensitivity and discrimination accuracy of the distribution terminal to fault distance in impedance discontinuous scenarios, filling the technical gap in existing testing methods that generally neglect the assessment of "segment selection capability." The fault simulation device, according to the test plan, sequentially triggers various single-phase grounding faults at preset fault points, achieving full coverage testing of fault types.

[0031] Furthermore, in step S5, the power distribution terminal is a feeder terminal unit (FTU), which acts as a data acquisition unit. It collects its own response data and alarm signals in real time after each fault is triggered, and uploads the data to the power distribution master station through an encrypted wireless communication network to ensure the real-time performance and security of data transmission.

[0032] Furthermore, in step S6, the power distribution master station is a control system capable of realizing functions such as power distribution network data acquisition and monitoring, analysis and fault handling. It has a built-in quantitative evaluation module, which first determines whether the terminal judgment is correct according to preset standards: the terminal located in the upstream section of the fault point should reliably generate a small current grounding alarm signal and successfully send it to the master station to be considered as correct judgment, and the terminal in the downstream section of the fault point is not allowed to generate a small current grounding alarm signal to be considered as correct judgment.

[0033] Based on this, a differentiated scoring principle is adopted: for fault points F1 and F7 that assess line selection ability, 0.5 points are awarded if a single tested terminal correctly identifies the fault, and 1 point is awarded if both terminals correctly identify the fault; for fault point F6 that assesses segment selection ability, since it is necessary to assess the collaborative analysis ability of multiple terminals, 1 point is awarded if both tested terminals correctly identify the fault.

[0034] The ranking adopts a multi-dimensional selection rule: when the total scores are the same, the one with fewer false alarms is given priority; when the number of false alarms is the same, the one with fewer missed alarms is given priority, so as to achieve accurate and objective ranking of the terminal's judgment capabilities.

[0035] like Figure 1-3 As shown, a testing system and method for assessing single-phase grounding faults in distribution terminals based on a full-scale test platform are described. The specific implementation process is as follows: (1) Communication Environment Setup and Equipment Testing: An encrypted wireless communication environment was set up based on the integrated low-voltage and medium-voltage real-world demonstration platform and the power distribution master station. A wireless communication module was added to the front-end server, and an IoT card with a fixed IP address was activated. Encrypted data transmission between the power distribution terminal and the front-end encryption machine was achieved through a dedicated VPN. The master station and the front-end server were connected via network cable. The integrated primary and secondary pole-mounted circuit breakers were wired and placed in sequence outside the real-world demonstration site. The insulation performance of the equipment was tested using an insulation megohmmeter, and the continuity of the test circuit and the contact of the wiring terminals were tested using a multimeter. At the same time, the grounding resistance of the power distribution terminal was tested to ensure that the basic condition of all test equipment met the standards.

[0036] (2) Construction of a real-world test site and selection of test lines: A real-world test site with diverse grid structures is constructed and equipped with a neutral grounding adjustment device, which can flexibly switch between ungrounded and grounded modes via an arc suppression coil. A 13kM overhead-cable hybrid line formed by the combination of 10kV overhead test line II and 10kV cable test line III is selected as the test line. This line can simulate the reflection and refraction of fault traveling waves at the impedance discontinuity interface, the sudden change in wave impedance, and the phenomenon of traveling wave distortion, which is consistent with the actual distribution network in urban and rural areas.

[0037] (3) Electromagnetic and load environment simulation: A programmable harmonic source based on 72 hours of measured data from a textile factory in Fujian Province was selected. This source can play back real waveforms with a THD average of 8.2% and rich in 5th / 7th / 11th harmonics. It was simultaneously connected to the bus side of the test line and the upstream section of the fault point. A dual-mode coupling method of current injection and voltage superposition was adopted to simulate harmonic interference on site. Simultaneously, a simulated load device was connected, and the load current was adjusted according to the load characteristics of the distribution network on site to simulate actual load fluctuations and construct a highly realistic electromagnetic and load environment.

[0038] (4) Fault triggering: F1 fault point is set in the middle section of the test line, F7 fault point is set at the end, and F6 fault point is set at the overhead-cable transition node. The non-faulty line on the same bus is used as the test object for faults outside the zone. Through the single-phase grounding fault simulation device, according to Figure 2 The 22 test items sequentially trigger different types of single-phase grounding faults at each fault point, including ungrounded / grounded via arc suppression coil, sand / tree / arc grounding medium, and non-metallic grounding faults with different transition resistances of 750-4000Ω. Among them, the arc grounding is an intermittent, short-time arc type, and the transition resistance is switched between 750Ω, 1000Ω, 1500Ω, 2000Ω, 2500Ω, 3000Ω, 3500Ω, and 4000Ω according to the test plan.

[0039] (5) Data acquisition and uploading: The feeder terminal under test (FTU) deployed at key nodes of the test line collects its own response data and low current grounding alarm signal after each fault is triggered in real time. Through an encrypted wireless communication network, the data is uploaded to the power distribution master station in real time and securely. The master station stores and backs up all data to ensure data traceability.

[0040] (6) Quantitative evaluation and ranking: The distribution master station judges the correctness of the terminal analysis based on the preset standards: the upstream terminal of the fault point reliably sends an alarm signal and the downstream terminal has no alarm signal, which is considered a correct analysis. Then, the scoring is carried out according to the differentiated scoring principle: F1 / F7 gets 0.5 points for a single fault point analysis correctly, and 1 point for both correctly analyzed; F6 gets 1 point for both terminals analyzing the fault point correctly. Finally, the ranking is sorted according to the multi-dimensional ranking rules: the higher the total score, the higher the score if the scores are the same, the lower the number of false alarms, and the lower the number of missed alarms if the number of false alarms is the same.

[0041] After the test is completed, a complete test report is generated, which includes the scores, rankings, fault diagnosis details, performance shortcomings, etc. of each terminal, providing reliable practical and data basis for equipment selection, algorithm optimization and improvement of distribution network fault handling capabilities.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A test method for assessing the ability to diagnose single-phase grounding faults in distribution terminals based on a full-scale test platform, characterized in that, Includes the following steps: S1: Based on the real-world test site and the power distribution master station, an encrypted wireless communication environment is built to perform wiring, insulation, continuity and grounding tests on the power distribution terminal and related test equipment; S2: Construct a realistic test field with diverse grid structures and adjustable neutral grounding methods, and select an overhead-cable hybrid test line as the test line; S3: Connect to typical harmonic interference sources and simulated loads based on field measured data. Simulate the actual power grid electromagnetic environment by using dual-position access at the bus side and upstream of the fault point, and dual-mode coupling of current injection and voltage superposition. S4: Set up coordinated fault points in the middle section, end and overhead-cable transition nodes of the test line, and trigger single-phase grounding faults covering different neutral grounding methods, grounding medium types and 750-4000Ω continuously adjustable transition resistance through the fault simulation device. S5: Collect the response data and alarm signals of the tested power distribution terminal after each fault and upload them to the power distribution master station; S6: The power distribution master station quantifies and ranks the single-phase grounding fault line selection and segment selection capabilities of the tested terminals according to the preset scoring and ranking rules. In step S1, a wireless communication module is added to the front-end server and an IoT card with a fixed IP is activated. Encrypted data transmission between the terminal and the front-end encryption machine is achieved through a dedicated VPN. In step S6, the scoring rules distinguish between line selection and segment selection assessment dimensions. When the total scores are the same, the ranking rules select the best candidate based on the number of false alarms and the number of missed alarms.

2. The method for testing the ability to diagnose single-phase grounding faults in distribution terminals based on a full-scale test platform according to claim 1, characterized in that, The overhead-cable hybrid test line mentioned in step S2 is a combination of a 13kM 10kV overhead test line II and a 10kV cable test line III, which simulates the reflection and refraction of fault traveling waves at the impedance discontinuity interface, the sudden change in wave impedance, and the traveling wave distortion phenomenon.

3. The method for testing the ability to diagnose single-phase grounding faults in distribution terminals based on a full-scale test platform according to claim 1, characterized in that, The typical harmonic interference source mentioned in step S3 is a programmable harmonic source based on 72 hours of measured data from a textile factory in Fujian Province. The average total harmonic distortion rate of this scenario is 8.2%, and it is rich in 5th, 7th, and 11th harmonics, achieving a 1:1 true playback of harmonic waveforms.

4. The method for testing the ability to diagnose single-phase grounding faults in distribution terminals based on a full-scale test platform according to claim 1, characterized in that, The collaborative fault points mentioned in step S4 include the middle section F1, the end section F7, and the overhead-cable transition node F6 within the test line. F1 and F7 are used to assess the accuracy of fault line selection within the test area, F6 is used to assess the segment selection capability under impedance discontinuity scenarios, and the non-faulty lines on the same bus are used to assess the ability to prevent false alarms of faults outside the test area.

5. The method for testing the ability to diagnose single-phase grounding faults in distribution terminals based on a full-scale test platform according to claim 1, characterized in that, In step S4, the neutral point grounding method includes ungrounded method and grounding method via arc suppression coil. The grounding medium type includes sand and gravel medium, tree branch medium and arc grounding. Arc grounding is intermittent and short-time arc type.

6. The method for testing the ability to diagnose single-phase grounding faults in distribution terminals based on a full-scale test platform according to claim 1, characterized in that, The correct judgment criterion in step S6 is: the terminal in the upstream section of the fault point reliably generates and sends a small current grounding alarm signal, while the terminal in the downstream section of the fault point does not generate a small current grounding alarm signal.

7. The method for testing the ability to diagnose single-phase grounding faults in distribution terminals based on a full-scale test platform according to claim 4, characterized in that, The scoring principle described in step S6 is as follows: 0.5 points are awarded for correctly identifying a single fault point F1 or F7, and 1 point is awarded for correctly identifying both; 1 point is awarded for fault point F6 if both tested terminals are correctly identified.

8. A testing system for assessing single-phase grounding faults in distribution terminals based on a full-scale test platform, characterized in that, The method for testing the single-phase grounding fault assessment capability of a distribution terminal based on a full-scale test platform, as described in any one of claims 1-7, comprises a full-scale test unit, a communication network unit, an environmental simulation unit, a fault triggering unit, a data acquisition unit, and a quantitative evaluation unit. The full-scale test unit is a medium- and low-voltage integrated full-scale verification platform, including a multi-network structure with adjustable neutral grounding and a 13km overhead-cable hybrid test line, and is equipped with F1, F6, and F7 collaborative fault points. The communication network unit includes a distribution master station, a front-end server, a wireless communication module, an IoT card, and a front-end encryption device, which enables encrypted wireless data transmission between the distribution terminal and the master station via a dedicated VPN. The system includes a programmable harmonic source and a simulated load device. The harmonic source is configured based on actual measured data from the textile factory and uses a dual-position access and dual-mode coupling method to simulate a complex electromagnetic environment. The fault triggering unit is a single-phase grounding fault simulation device that can trigger single-phase grounding faults with different neutral point grounding methods, grounding medium types, and adjustable transition resistances of 750-4000Ω. The data acquisition unit is a measured distribution terminal unit (FTU) used to collect fault response data and upload alarm signals to the distribution master station. The quantitative evaluation unit is the evaluation module of the distribution master station, with built-in preset scoring and ranking rules to achieve quantitative scoring and ranking of the terminal's line selection and segment selection capabilities.

9. A test system for assessing single-phase grounding faults in distribution terminals based on a full-scale test platform, as described in claim 8, is characterized in that... The programmable harmonic source can realize 1:1 on-site waveform playback of total harmonic distortion rate and odd / even harmonic spectrum distribution, and the simulated load device can simulate the load current fluctuation characteristics of the actual power grid.

10. A test system for assessing single-phase grounding faults in distribution terminals based on a full-scale test platform, as described in claim 8, is characterized in that... The power distribution master station has the functions of power distribution network data acquisition and monitoring, fault data storage, quantitative evaluation of analysis capabilities and result display, and realizes full traceability and analysis of test data.

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