Power distribution network transient grounding protection test device and method

Abstract

The invention provides a power distribution network transient grounding protection testing device and method, and belongs to the technical field of power distribution network transient grounding protection testing. In order to solve the technical problem that the transient grounding protection function of the power distribution network secondary equipment cannot be accurately tested on site, a man-machine interaction module is sequentially connected with a digital modeling module, a simulation calculation module, a test management module and an automatic closed-loop test module through wires; the data storage module is connected with the test management module, the automatic closed-loop test module and the waveform self-inspection module through wires. The output end of the automatic closed-loop test module is connected with the protection device through the switch position output module. The output end of the automatic closed-loop test module is also connected with a self-recording module through a digital-to-analog conversion module and a power amplification and output module; the output end of the self-recording module is connected with a waveform self-checking module; the input end of the automatic closed-loop test module is connected with the protection device through the signal acquisition module; the method is applied to the transient grounding protection test of the power distribution network.

Description

Technical Field

[0001] This invention provides a device and method for testing transient grounding protection of distribution networks, belonging to the field of transient grounding protection testing technology for distribution networks. Background Technology

[0002] Distribution networks widely employ neutral-point non-effective grounding, making single-phase grounding faults their most prevalent fault type. For a long time, when a single-phase grounding fault occurs, to meet power supply requirements, power grid companies typically employ a strategy of operating with the fault for a period. However, due to the persistent arcing at the grounding point, this can easily lead to fires, electric shocks, and other accidents. With the increasing sophistication of distribution network structures and feeder automation technologies, technical guarantees have been provided for the rapid restoration of power supply after a fault. While ensuring power supply reliability, rapidly detecting and clearing single-phase grounding faults to reduce the occurrence of fires and electric shocks has become one of the main goals of current distribution network development.

[0003] In single-phase grounding faults, fault detection of low-current grounding in distribution networks is more difficult. Due to the small fault current, unstable grounding arc, and severe current waveform distortion in low-current grounding systems, coupled with the influence of multiple factors such as arc suppression coils and nonlinear unstable arcs, the correct operation rate of traditional protection based on steady-state power frequency quantities is less than 70%. In recent years, with the deepening understanding of the characteristics of distribution network grounding faults and the continuous development of high-speed data acquisition and processing technologies, grounding fault protection based on the transient power direction principle has been widely recognized and applied. However, the widespread application of transient grounding protection heavily relies on the reliability and accuracy of the protection device's operation. Unlike mature power frequency protection, the performance of transient protection is significantly affected by various factors such as fault closing angle, transition resistance, system operating mode, line parameters, and complex harmonics and noise generated by power electronic equipment in the power grid. The reliability of the core algorithms used (such as transient energy method, wavelet transform method, first half-wave method, transient group amplitude and phase comparison method, etc.) must be fully verified under various complex and extreme operating conditions.

[0004] Comprehensive performance testing of transient grounding protection devices mainly relies on laboratory dynamic model tests. Currently used field testing methods have the following technical problems:

[0005] I. Limited testing scenarios, making it difficult to simulate real-world complex operating conditions: Existing testing devices or methods mostly rely on simple steady-state signal sources or the playback of a few pre-recorded typical fault waveforms. This approach cannot flexibly and comprehensively simulate the combined effects of key factors such as fault initial phase angle, nonlinear changes in transition resistance, arc characteristics, differences in line parameters, and background noise on the protection action logic. This results in insufficient test coverage and an inability to fully expose the potential defects of protection devices under boundary conditions or extreme situations.

[0006] II. High Requirements for Transient Signal Fidelity and Synchronization: Transient protection relies on the characteristics of high-frequency, abrupt signal changes. Traditional test power supplies have limited output bandwidth, making it difficult to accurately reproduce the leading edge of transient processes that change at the nanosecond or microsecond level. Simultaneously, strict synchronization is required between the zero-sequence voltage and the zero-sequence current signals of multiple output lines. Any minute timing deviation can lead to incorrect conclusions from protection criteria based on direction or energy principles. Existing test systems suffer from bottlenecks in high-speed, multi-channel synchronous output.

[0007] Third, there is a lack of standardized and systematic testing methods: Currently, the industry lacks unified and scientific testing specifications and evaluation systems for transient grounding protection. Testers often rely on experience, and the design of test cases lacks systematicity and specificity, making it difficult to comprehensively and quantitatively evaluate the robustness, sensitivity, and speed of the protective device's operation.

[0008] Therefore, there is an urgent need to develop a transient grounding protection testing scheme suitable for production sites to meet the needs of verifying and improving the performance of transient grounding protection devices and promoting their engineering applications. Summary of the Invention

[0009] To address the technical problems existing in the background art, the present invention adopts the following technical solution: A transient grounding protection testing device for a distribution network is provided, comprising a human-machine interaction module, a digital modeling module, a simulation calculation module, a test management module, an automatic closed-loop test module, a data storage module, a waveform recording module, a waveform self-testing module, and a protection device, wherein:

[0010] The human-computer interaction module is connected sequentially to the digital modeling module, simulation calculation module, test management module, and automatic closed-loop test module via the PCIE bus. The data storage module has built-in data of line parameter database, fault model library, calculation case library, and test discrimination test cases for retrieval. The data storage module is connected to the test management module, automatic closed-loop test module, and waveform self-test module via the PCIE bus.

[0011] The output of the automatic closed-loop test module is connected to the protection device through a switch position output module.

[0012] The output of the automatic closed-loop test module is also connected to the self-recording waveform module through a digital-to-analog converter module, a power amplifier and output module, and the output of the self-recording waveform module is connected to the waveform self-test module.

[0013] The input terminal of the automatic closed-loop test module is connected to the protection device through a signal acquisition module;

[0014] The human-computer interaction module is also connected to a real-time display module and a test report generation module.

[0015] A test method for a transient grounding protection test device for a distribution network is provided. The tester inputs the distribution network topology parameters through a human-machine interaction module. The human-machine interaction module transmits the input distribution network topology parameters to a digital modeling module. The digital modeling module completes the analysis of distribution network topology parameters and the construction of digital models for various line conditions by calling the line parameter database and the fault model library.

[0016] The simulation calculation module completes simulation calculations under various faults through the pre-defined case library and outputs fault waveforms to the test management module. The test management module transmits the fault waveforms to the automatic closed-loop test module according to preset instructions and simultaneously maps and stores them to the data storage module.

[0017] The automatic closed-loop test module inputs the digital signal of the switch position to the protection device through the switch position output module. At the same time, it transmits the fault waveform to the protection device through the digital-to-analog conversion module and the power amplifier and output module. By calling the test discrimination test cases and the switch signal of the protection device acquired by the signal acquisition module, it automatically judges and records the action of the protection device in response to the fault waveform. Finally, the test results are stored in the data storage module.

[0018] The self-recording waveform module acquires the fault voltage and current waveforms output by the power amplifier and output module and inputs them to the waveform self-test module. The waveform self-test module has a built-in waveform analysis program that compares the fault waveforms of the data storage module and the self-recording waveform module to check whether the distortion of the output waveform of the power amplifier and output module meets the requirements.

[0019] The control real-time display module collects the waveform distortion self-test results output by the waveform self-test module, as well as the fault waveforms output by the power amplification and output modules collected by the self-recording module, and displays them in the human-machine interaction module in real time.

[0020] The control test report generation module collects test waveforms and results information of different fault types stored in the data storage module, automatically edits and generates test reports according to the predefined modules, and transmits them to the human-computer interaction module.

[0021] For cases where the tested line is purely overhead or purely cable, the digital modeling module performs distribution network topology parameter analysis and digital model construction as follows:

[0022] When a line is protected by multiple line protection devices or feeder terminals forming an N-level transient grounding protection system, the lengths of each line in the system are s1, s2, s3, ..., s n The CTs at the protection installation locations are CT1, CT2, CT3...CT N The corresponding zero-sequence currents flowing through the CT are i 0k1 i 0k2 i 0k3···i 0kN The distance between each CT level and the next CT level or the end of the line, as well as the segment capacitance value, are s, respectively. k1 s k2 s k3 ···s kn and C k1 C k2 C k3 ···C kN The spatial distance between the fault point and the busbar is l k Then the capacitance value C of the Nth segment kN The calculation formula is:

[0023] ;

[0024] The capacitance C of the line between the fault point and the busbar k The calculation formula is:

[0025] .

[0026] For the case of a mixed line consisting of various types of overhead conductors and cables, the digital modeling module performs the following specific method for analyzing distribution network topology parameters and constructing a digital model:

[0027] Based on the overhead conductor or cable type and length input from the human-computer interaction module, the capacitance value per unit length to ground corresponding to different overhead conductor or cable types is obtained by consulting the line parameter database, and then the capacitance value C of each segment of the tested line is calculated. kN ;

[0028] Suppose there are n overhead conductors or cables of different types between CTN-1 and CTN, with capacitance to ground per unit length and length respectively being A1, A2, A3...A n and s j1 s j2 s j3 ··s jn Then the capacitance value C of the (N-1)th segment k(N-1) The calculation formula is:

[0029] .

[0030] For cases where the tested line is purely overhead or purely cable, the digital modeling module performs the following specific methods for analyzing distribution network topology parameters and constructing a digital model:

[0031] When a line is composed of multiple line protectors or feeder terminals forming an N-level transient grounding protection system, the lengths of each line in the system are s1, s2, s3...s n The CTs at the protection installation locations are CT1, CT2, CT3...CTN The corresponding zero-sequence currents flowing through the CT are i 0k1 i 0k2 i 0k3 ···i 0kN The distance between each CT level and the next CT level or the end of the line, as well as the segment capacitance value, are s, respectively. k1 s k2 s k3 ···s kn and C k1 C k2 C k3 ···C kN The spatial distance between the fault point and the busbar is l k Then the capacitance value C of the Nth segment kN The calculation formula is:

[0032] ;

[0033] The capacitance C of the line between the fault point and the busbar k The calculation formula is:

[0034] .

[0035] For the case where the tested line is a neutral-point ungrounded system, the digital modeling module performs the following specific methods for analyzing distribution network topology parameters and constructing a digital model:

[0036] The system model is constructed based on whether the tested line is purely overhead or purely cabled, with neutral point k. L With k R With the switch open, draw the zero-sequence equivalent network. Based on the zero-sequence equivalent network, construct the following voltage and current:

[0037] ;

[0038] Solving for the given information, we get:

[0039] ;

[0040] The expression for the current sensed by the CT at each protection installation point in the system is:

[0041] ;

[0042] Among them, u A R is the electromotive force of the power source. g For the transition resistance at the grounding fault point, u C i represents the voltage value to ground at the fault point. k This represents the current flowing through the fault point.

[0043] For the case where the tested line is a neutral-point grounded system via an arc-suppression coil, the specific method for performing distribution network topology parameter analysis and digital model construction in the digital modeling module is as follows:

[0044] The system model is constructed based on whether the tested line is purely overhead or purely cabled, with neutral point k. L Closed, k R With the switch open, draw the zero-sequence equivalent network. Based on the zero-sequence equivalent network, construct the following voltage and current:

[0045] ;

[0046] By constructing the second-order differential equation, we can obtain:

[0047] ;

[0048] The solution yields:

[0049] ;

[0050] Among them, s 1,2 The characteristic root is calculated using the following formula:

[0051] ;

[0052] ω n The natural oscillation frequency is calculated using the following formula:

[0053] ;

[0054] ζ is the system damping, and its calculation formula is:

[0055] ;

[0056] The formula for calculating the current sensed by each CT is:

[0057] ;

[0058] Where: u A R is the electromotive force of the power source. g For the transition resistance at the grounding fault point, u C i represents the voltage value to ground at the fault point. k i is the current value flowing through the fault point. C Let i be the system capacitance current to ground. L This is the current flowing through the arc suppression coil.

[0059] The digital modeling module uses intermittent arc fault models from the fault model library, combined with the modeling method for the grounding method of the corresponding tested line, to perform distribution network topology parameter analysis and digital model construction. The specific method is as follows:

[0060] Intermittent arc faults are simulated using the following method:

[0061] Step 8.1: Construct the following arc model equations, expressed as:

[0062] ;

[0063] Where g=1 / R g It is the arc conductance, R g For the transition resistance at the grounding fault point, u C i represents the voltage value to ground at the fault point. k The current flowing through the fault point is τ, where τ is the arc time constant and P0 is the arc heat dissipation power constant.

[0064] Step 8.2: Solve the equations from Step 8.1 together with the current equations of each CT under the conditions of neutral point ungrounded and neutral point grounded through arc suppression coil to obtain the intermittent arc grounding fault waveforms of each CT.

[0065] The waveform analysis program built into the waveform self-test module is used to execute a transient waveform extraction and playback method based on the S-transform, including:

[0066] Step 9.1: Load the COMTRADE format waveform file, parse and extract information from the raw data, and form... Waveform information equations based on time-domain information;

[0067] Where A is the amplitude of the acquired signal; Angular frequency, ; B represents the initial phase; B represents the DC bias.

[0068] Step 9.2: For the original waveform signal After performing the S-transform, the time-frequency characteristic equation The expression is:

[0069] ;

[0070] Where: t is time; It is a time index; f is the frequency; It is a Gaussian function, and its width is determined by the frequency f;

[0071] Step 9.3: Obtain the time-frequency matrix based on amplitude and phase characteristics, including:

[0072] According to the time-frequency characteristic equation By using the discrete S-transform formula, the complex values ​​at each time point τ and each frequency point f are calculated to form a time-domain matrix. ;

[0073] Calculate the time-frequency matrix The modulus value in the middle is obtained ;

[0074] Obtain time-frequency feature values, where the amplitude feature is: Phase characteristics are ;

[0075] Step 9.4: For the original waveform signal After S-transformation, a new [structure] is formed. Waveform data, based on the playback function, enables high-speed and efficient playback of transient data.

[0076] The waveform analysis program built into the waveform self-test module is used to execute a dual-certification automatic test method based on waveform playback, including:

[0077] Step 10.1: After loading the original transient waveform, extract the signal to form the original data. ;

[0078] Step 10.2: Forming the time-domain matrix after S-transformation And extract amplitude and phase features;

[0079] Step 10.3: Based on the time-domain matrix dataset Perform waveform playback and simultaneously record the output waveform to form a new time-domain matrix. ;

[0080] Step 10.4: First round of authentication, comparing and replaying waveform data. Waveform data acquired by recording If they are consistent, it means there is no problem with the playback system; if they are inconsistent, it means there is an anomaly in the playback system, and the relevant judgment ends.

[0081] Step 10.5: After the first round of certification is successful, the second round of testing and certification will be conducted. The test will be judged as qualified based on whether the automatic test model and the collected protection output switch positions are consistent. If the protection output positions are consistent, the test will be judged as qualified; otherwise, the test will be judged as failed.

[0082] Step 10.6: Summarize the overall test results to generate a test report, and end the overall process.

[0083] The beneficial effects of this invention compared to the prior art are as follows: This invention provides a transient grounding protection test scheme for distribution networks. By employing S-transform transient waveform extraction and playback methods, fault modeling and simulation verification methods, waveform playback-based dual-certification automatic testing methods, and database-based test case management methods, it enables the testing of transient grounding selection or protection functions of secondary equipment such as distribution network production site protection devices, low-current grounding selection devices, and feeder automation terminals. This solves the technical problem that the transient grounding protection function of secondary equipment in distribution networks cannot be accurately quantified and tested on-site. Attached Figure Description

[0084] The present invention will be further described below with reference to the accompanying drawings:

[0085] Figure 1 This is a schematic diagram of the structure of the power distribution network transient grounding protection test device of the present invention;

[0086] Figure 2 The circuit diagram shown in this embodiment of the invention is either a purely overhead line or a purely cable line.

[0087] Figure 3 The circuit diagram shown in this embodiment of the invention is a mixed circuit composed of various types of overhead conductors and cables.

[0088] Figure 4 This is a circuit diagram of a neutral-point ungrounded system in an embodiment of the present invention.

[0089] Figure 5 This is a circuit diagram of a neutral point grounded system via an arc suppression coil, as shown in this embodiment of the invention.

[0090] Figure 6 This is a flowchart illustrating the steps of the transient waveform extraction and playback method based on S-transform of the present invention.

[0091] Figure 7 This is a flowchart illustrating the steps of the automatic dual-certification testing method based on waveform playback of the present invention.

[0092] Figure 8 This is a flowchart illustrating the steps of the database-based test case management method of the present invention. Detailed Implementation

[0093] To address the technical problem of inaccurate on-site testing of transient grounding protection functions of secondary equipment in power distribution networks, this invention proposes a transient grounding protection testing device and method for power distribution networks. This device can test the transient grounding selection or protection functions of secondary equipment such as on-site protection devices, low-current grounding selection devices, and feeder automation terminals in power distribution networks.

[0094] like Figure 1As shown, the power distribution network transient grounding protection testing device provided by this invention includes: a human-machine interaction module, a digital modeling module, a simulation calculation module, a test management module, an automatic closed-loop test module, a data storage module, a line parameter database, a fault model library, a calculation case library, test discrimination cases, a switch position output module, a signal acquisition module, a protection device, a digital-to-analog conversion module, a power amplification and output module, a waveform recording module, a waveform self-testing module, a real-time display module, and a test report generation module, wherein:

[0095] The test personnel input the distribution network topology parameters through the human-machine interaction module, which then transmits the parameters to the digital modeling module. The digital modeling module then uses the line parameter database and fault model library to complete the parsing of the distribution network topology parameters and the construction of the digital model.

[0096] Furthermore, the testers input distribution network topology parameters through the human-machine interface module. These parameters mainly include: system voltage level U. n Protection device setting I d Measured capacitance currents of the circuit (I1, I2, I3...I) n ), measured capacitance current I of busbar and main transformer m Line lengths (s1, s2, s3...s) n Line parameters include overhead line conductor type, wire diameter, cable type, material, interface and length, neutral point arc suppression coil inductance value L0, neutral point resistance value R0, etc.

[0097] The simulation calculation module completes simulation calculations under various faults through the pre-defined case library and outputs fault waveforms to the test management module. The test management module transmits the fault waveforms to the automatic closed-loop test module according to preset instructions and simultaneously maps and stores them to the data storage module.

[0098] The automatic closed-loop test module inputs digital signals such as switch position to the protection device through the switch position output module. At the same time, it transmits the fault waveform to the protection device through the digital-to-analog conversion module and the power amplifier and output module. By calling the test discrimination cases and the switch signals of the protection device collected by the signal acquisition module, it automatically judges and records the action of the protection device in response to the fault waveform. Finally, the test results are stored in the data storage module.

[0099] The self-recording waveform module acquires the fault voltage and current waveforms output by the power amplifier and output module and inputs them to the waveform self-test module. The waveform self-test module has built-in waveform analysis software, which compares the fault waveforms of the data storage module and the self-recording waveform module to check whether the distortion of the output waveform of the power amplifier and output module meets the requirements.

[0100] The real-time display module collects the waveform distortion and other self-test results output by the waveform self-test module, as well as the fault waveforms output by the power amplification and output modules collected by the self-recording module, and displays them in the human-machine interaction module in real time.

[0101] The test report generation module collects test waveforms and results of different fault types stored in the data storage module, automatically edits and generates test reports according to the predefined modules, and transmits them to the human-computer interaction module.

[0102] Furthermore, let the three-phase capacitances to ground of the line and busbar be C respectively. 01 C 02 C 03 ···C 0n and C 0m Angular frequency ω = 2πf (f is the system frequency; for a 50Hz system, ω ≈ 314 rad / s), based on the system voltage level U n The system average voltage U is obtained by looking up a table (stored in the line parameter database). av (e.g., 10.5kV, 37kV, etc.), then the formula for calculating the capacitance to ground of this line or busbar is:

[0103] ;

[0104] .

[0105] Furthermore, for the tested line that is purely overhead or purely cable, when the line is protected by multiple line protection units or feeder terminals forming an N-level transient grounding protection system, the modeling should be performed as follows:

[0106] like Figure 2 As shown, the lengths of each line in the system are s1, s2, s3...s n The CTs at the protection installation locations are CT1, CT2, CT3...CT N The corresponding zero-sequence currents flowing through the CT are i 0k1 i 0k2 i 0k3 ···i 0kN The distance between each CT level and the next CT level or the end of the line, as well as the segment capacitance value, are s, respectively. k1 s k2 s k3 ···s kn and C k1 C k2 C k3 ···C kN The spatial distance between the fault point and the busbar is l k Then the capacitance value C of the Nth segment kNThe calculation formula is:

[0107] ;

[0108] The capacitance C of the line between the fault point and the busbar k The calculation formula is:

[0109] .

[0110] Furthermore, for mixed lines composed of various types of overhead conductors and cables, the capacitance per unit length to ground corresponding to different overhead conductor or cable types can be obtained by consulting the line parameter database based on the overhead conductor or cable type and length input into the human-machine interface module. This allows for the calculation of the capacitance C of each segment of the tested line. kN Modeling should be performed using the following method:

[0111] like Figure 3 As shown, there are n overhead conductors or cables of different types between CTN-1 and CTN, with capacitance to ground per unit length and lengths A1, A2, A3, ..., A... n and s j1 s j2 s j3 ··s jn Then the capacitance value C of the (N-1)th segment k(N-1) The calculation formula is:

[0112] .

[0113] Furthermore, for the tested line that is purely overhead or purely cable, when the line is protected by multiple line protection units or feeder terminals forming an N-level transient grounding protection system, the modeling should be performed as follows:

[0114] The lengths of the lines in the system are s1, s2, s3, ... s n The CTs at the protection installation locations are CT1, CT2, CT3...CT N The corresponding zero-sequence currents flowing through the CT are i 0k1 i 0k2 i 0k3 ···i 0kN The distance between each CT level and the next CT level or the end of the line, as well as the segment capacitance value, are s, respectively. k1 s k2 s k3 ···s kn and C k1 C k2 C k3 ···C kN The spatial distance between the fault point and the busbar is lk Then the capacitance value C of the Nth segment kN The calculation formula is:

[0115] ;

[0116] The capacitance C of the line between the fault point and the busbar k The calculation formula is:

[0117] .

[0118] Furthermore, for a neutral-point ungrounded system, based on the system model in the second step, the neutral point k L With k R With the switch off, draw the zero-sequence isonet and model it using the following method:

[0119] like Figure 4 As shown, based on the zero-sequence equivalent network, the following voltage and current are constructed, where u A R is the electromotive force of the power source. g For the transition resistance at the grounding fault point, u C i represents the voltage value to ground at the fault point. k If the current flowing through the fault point is the value, then the following condition must be met:

[0120] ;

[0121] Solving for the given information, we get:

[0122] ;

[0123] The expression for the current sensed by the CT at each protection installation point in the system is:

[0124] .

[0125] Furthermore, for a neutral point grounded via an arc suppression coil, based on the system model from step two above, the neutral point k... L Closed, k R With the switch off, draw the zero-sequence isonet and model it using the following method:

[0126] like Figure 5 As shown, based on the zero-sequence equivalent network, the following voltage and current are constructed, where:

[0127] u A R is the electromotive force of the power source. g For the transition resistance at the grounding fault point, u C i represents the voltage value to ground at the fault point. k i is the current value flowing through the fault point. C Let i be the system capacitance current to ground. LIf the current flowing through the arc suppression coil is , then the following condition is satisfied:

[0128] ;

[0129] By constructing the second-order differential equation, we can obtain:

[0130] ;

[0131] The solution yields:

[0132] ;

[0133] Among them, s 1,2 The characteristic root is calculated using the following formula:

[0134] ;

[0135] ω n The natural oscillation frequency is calculated using the following formula:

[0136] ;

[0137] ζ is the system damping, and its calculation formula is:

[0138] ;

[0139] The formula for calculating the current sensed by each CT is:

[0140] .

[0141] Furthermore, this invention simulates intermittent arc faults using the following method:

[0142] Step 1: Construct the following arc model equations, expressed as:

[0143] ;

[0144] Where g=1 / R g It is the arc conductance, R g For the transition resistance at the grounding fault point, u C i represents the voltage value to ground at the fault point. k Let τ be the current flowing through the fault point, τ be the arc time constant, and P0 be the arc heat dissipation power constant.

[0145] Step 2: Solve the equations from Step 1 together with the aforementioned CT current equations to obtain the intermittent arcing ground fault waveforms for each CT.

[0146] Furthermore, such as Figure 6As shown, the transient waveform extraction and playback method based on S-transform provided by this invention specifically obtains the time-domain matrix information elements of a COMTRADE format waveform recording file using the S-transform-based transient waveform extraction method. The steps include:

[0147] Step 1: Load the COMTRADE format waveform file, parse and extract information from the raw data, and form... Waveform information equations based on time-domain information;

[0148] Where A is the amplitude of the acquired signal; Angular frequency, ; B represents the initial phase; B represents the DC bias.

[0149] Step 2: For the original waveform signal After performing the S-transform, the time-frequency characteristic equation The expression is:

[0150] ;

[0151] Where: t is time; It is a time index; f is the frequency; It is a Gaussian function, and its width is determined by the frequency f;

[0152] Step 3: Obtain the time-frequency matrix based on amplitude and phase features, including:

[0153] According to the time-frequency characteristic equation By using the discrete S-transform formula, the complex values ​​at each time point τ and each frequency point f are calculated to form a time-domain matrix. ;

[0154] Calculate the time-frequency matrix The modulus value in the middle is obtained ;

[0155] Obtain time-frequency feature values, where the amplitude feature is: Phase characteristics are ;

[0156] Step 4: For the original waveform signal After S-transformation, a new [structure] is formed. Waveform data, based on the playback function, enables high-speed and efficient playback of transient data.

[0157] Furthermore, such as Figure 7 As shown, the automatic dual-certification testing method based on waveform playback of the present invention includes:

[0158] Step 1: After loading the original transient waveform, extract the signal to form the original data. ;

[0159] Step 2: Forming the time-domain matrix after S-transformation And extract amplitude and phase features;

[0160] Step 3: Based on the time-domain matrix dataset Perform waveform playback and simultaneously record the output waveform to form a new time-domain matrix. ;

[0161] Step 4: First round of authentication, comparing and replaying waveform data Waveform data acquired by recording If they are consistent, it means there is no problem with the playback system; if they are inconsistent, it means there is an anomaly in the playback system, and the relevant judgment ends.

[0162] Step 5: After the first round of certification is successful, the second round of testing and certification will be conducted. The test will be judged based on whether the automatic test model and the collected protection output switch positions are consistent. If the protection output positions are consistent, the test will be judged as qualified; otherwise, the test will be judged as failed.

[0163] Step 6: Summarize the overall test results to generate a test report, and end the overall process.

[0164] like Figure 8 As shown, the present invention also provides a database-based test case management method, including:

[0165] To implement a multi-database management approach, separate waveform databases, automated test rule bases, and test execution case bases are established, including:

[0166] The waveform use case library mainly extracts the feature information of each waveform from the list of original waveform files, including the amplitude, phase, frequency, duration, triggering event, polarity, coefficient, channel name and other information of electrical quantities, as well as the generation time and name of the waveform file. Based on the waveform feature information, a fault waveform dataset library is formed for both inside and outside the area.

[0167] The automatic test case library is combined with the hardware part of the test device. First, the basic test device output signal source and the mapping configuration rule model for the signals collected by the device under test are established. Based on the configuration rule model, automatic test discrimination rules for faults inside and outside the zone are set. For different projects, a test project list engineering management model library is built. During the test, the results of different test projects can generate a unified test report.

[0168] For waveform databases and automatic test rule bases, raw waveforms and test items are mapped to test case engineering files through waveform data and test rule mapping, and output channels and acquisition channels mapping. Test case engineering files are stored in test execution case library. After software and manual verification, relevant test engineering case files form test case data engineering file data sources that can be directly executed by test instruments, realizing a data maintenance and management method that can be quickly called based on different test instruments.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A test device for transient grounding protection in a power distribution network, characterized in that: It includes a human-computer interaction module, a digital modeling module, a simulation calculation module, a test management module, an automatic closed-loop test module, a data storage module, a waveform recording module, a waveform self-testing module, and a protection device, among which: The human-computer interaction module is connected sequentially to the digital modeling module, simulation calculation module, test management module, and automatic closed-loop test module via the PCIE bus. The data storage module has built-in data of line parameter database, fault model library, calculation case library, and test discrimination test cases for retrieval. The data storage module is connected to the test management module, automatic closed-loop test module, and waveform self-test module via the PCIE bus. The output of the automatic closed-loop test module is connected to the protection device through a switch position output module. The output of the automatic closed-loop test module is also connected to the self-recording waveform module through a digital-to-analog converter module, a power amplifier and output module, and the output of the self-recording waveform module is connected to the waveform self-test module. The input terminal of the automatic closed-loop test module is connected to the protection device through a signal acquisition module; The human-computer interaction module is also connected to a real-time display module and a test report generation module.

2. The test method for a transient grounding protection test device for a distribution network according to claim 1, characterized in that: The test personnel input the distribution network topology parameters through the human-computer interaction module. The human-computer interaction module transmits the input distribution network topology parameters to the digital modeling module. The digital modeling module completes the analysis of distribution network topology parameters and the construction of digital models for various line conditions by calling the line parameter database and the fault model library. The simulation calculation module completes simulation calculations under various faults through the pre-defined case library and outputs fault waveforms to the test management module. The test management module transmits the fault waveforms to the automatic closed-loop test module according to preset instructions and simultaneously maps and stores them to the data storage module. The automatic closed-loop test module inputs the digital signal of the switch position to the protection device through the switch position output module. At the same time, it transmits the fault waveform to the protection device through the digital-to-analog conversion module and the power amplifier and output module. By calling the test discrimination test cases and the switch signal of the protection device acquired by the signal acquisition module, it automatically judges and records the action of the protection device in response to the fault waveform. Finally, the test results are stored in the data storage module. The self-recording waveform module acquires the fault voltage and current waveforms output by the power amplifier and output module and inputs them to the waveform self-test module. The waveform self-test module has a built-in waveform analysis program that compares the fault waveforms of the data storage module and the self-recording waveform module to check whether the distortion of the output waveform of the power amplifier and output module meets the requirements. The control real-time display module collects the waveform distortion self-test results output by the waveform self-test module, as well as the fault waveforms output by the power amplification and output modules collected by the self-recording module, and displays them in the human-machine interaction module in real time. The control test report generation module collects test waveforms and results information of different fault types stored in the data storage module, automatically edits and generates test reports according to the predefined modules, and transmits them to the human-computer interaction module.

3. The test method for a transient grounding protection test device for a distribution network according to claim 2, characterized in that: For cases where the tested line is purely overhead or purely cable, the digital modeling module performs distribution network topology parameter analysis and digital model construction as follows: When the line is composed of multiple line protection devices or feeder terminals forming an N-level transient grounding protection system, the lengths of each line in the system are s1, s2, s3...s n The protective installation locations are CT1, CT2, CT3...CT N The corresponding zero-sequence currents flowing through the CT are i 0k1 i 0k2 i 0k3 ···i 0kN The distance between each CT level and the next CT level or the end of the line, as well as the segment capacitance value, are s, respectively. k1 s k2 s k3 ···s kn and C k1 C k2 C k3 ···C kN The spatial distance between the fault point and the busbar is l k Then the capacitance value C of the Nth segment kN The calculation formula is: ； The capacitance C of the line between the fault point and the busbar k The calculation formula is: 。 4. The test method for a transient grounding protection test device for a distribution network according to claim 2, characterized in that: For the case of a mixed line consisting of various types of overhead conductors and cables, the digital modeling module performs the following method for analyzing distribution network topology parameters and constructing a digital model: Based on the overhead conductor or cable type and length input from the human-computer interaction module, the capacitance value per unit length to ground corresponding to different overhead conductor or cable types is obtained by consulting the line parameter database, and then the capacitance value C of each segment of the tested line is calculated. kN ; Suppose there are n overhead conductors or cables of different types between CTN-1 and CTN, with capacitance to ground per unit length and length respectively being A1, A2, A3...A n and s j1 s j2 s j3 ··s jn Then the capacitance value C of the (N-1)th segment k(N-1) The calculation formula is: 。 5. The test method for a transient grounding protection test device for a distribution network according to claim 2, characterized in that: For cases where the tested line is purely overhead or purely cable, the digital modeling module performs the following specific methods for analyzing distribution network topology parameters and constructing a digital model: When a line is composed of multiple line protectors or feeder terminals forming an N-level transient grounding protection system, the lengths of each line in the system are s1, s2, s3...s n The protective installation locations are CT1, CT2, CT3...CT N The corresponding zero-sequence currents flowing through the CT are i 0k1 i 0k2 i 0k3 ···i 0kN The distance between each CT level and the next CT level or the end of the line, as well as the segment capacitance value, are s, respectively. k1 s k2 s k3 ···s kn and C k1 C k2 C k3 ···C kN The spatial distance between the fault point and the busbar is l k Then the capacitance value C of the Nth segment kN The calculation formula is: ； The capacitance C of the line between the fault point and the busbar k The calculation formula is: 。 6. The test method for a transient grounding protection test device for a distribution network according to claim 3, characterized in that: For the case where the tested line is a neutral-point ungrounded system, the digital modeling module performs the following specific methods for analyzing distribution network topology parameters and constructing a digital model: The system model is constructed based on whether the tested line is purely overhead or purely cabled, with neutral point k. L With k R With the switch open, draw the zero-sequence equivalent network. Based on the zero-sequence equivalent network, construct the following voltage and current: ； Solving for the given information, we get: ； The expression for the current sensed by the CT at each protection installation point in the system is: ； Among them, u A R is the electromotive force of the power source. g For the transition resistance at the ground fault point, u C i represents the voltage value to ground at the fault point. k This represents the current flowing through the fault point.

7. The test method for a transient grounding protection test device for a distribution network according to claim 3, characterized in that: For the case where the tested line is a neutral-point grounded system via an arc-suppression coil, the specific method for performing distribution network topology parameter analysis and digital model construction in the digital modeling module is as follows: The system model is constructed based on whether the tested line is purely overhead or purely cabled, with neutral point k. L Closed, k R With the switch open, draw the zero-sequence equivalent network. Based on the zero-sequence equivalent network, construct the following voltage and current: ； By constructing the second-order differential equation, we can obtain: ； The solution yields: ； Among them, s 1,2 The characteristic root is calculated using the following formula: ； ω n The natural oscillation frequency is calculated using the following formula: ； ζ is the system damping, and its calculation formula is: ； The formula for calculating the current sensed by each CT is: ； Where: u A R is the electromotive force of the power source. g For the transition resistance at the ground fault point, u C i represents the voltage value to ground at the fault point. k i is the current value flowing through the fault point. C Let i be the system capacitance current to ground. L This is the current flowing through the arc suppression coil.

8. A test method for a transient grounding protection test device for a distribution network according to any one of claims 3, 4, 5, 6, and 7, characterized in that: The digital modeling module uses intermittent arc fault models from the fault model library, combined with the modeling method for the grounding method of the corresponding tested line, to perform distribution network topology parameter analysis and digital model construction. The specific method is as follows: Intermittent arc faults are simulated using the following method: Step 8.1: Construct the following arc model equations, expressed as: ； Where g=1 / R g It is the arc conductance, R g For the transition resistance at the ground fault point, u C i represents the voltage value to ground at the fault point. k The current flowing through the fault point is τ, where τ is the arc time constant and P0 is the arc heat dissipation power constant. Step 8.2: Solve the equations from Step 8.1 together with the current equations of each CT under the conditions of neutral point ungrounded and neutral point grounded through arc suppression coil to obtain the intermittent arc grounding fault waveforms of each CT.

9. The test method for a transient grounding protection test device for a distribution network according to claim 2, characterized in that: The waveform analysis program built into the waveform self-test module is used to execute a transient waveform extraction and playback method based on the S-transform, including: Step 9.1: Load the COMTRADE format waveform file, parse and extract information from the raw data, and form... Waveform information equations based on time-domain information; Where A is the amplitude of the acquired signal; Angular frequency, ; B represents the initial phase; B represents the DC bias. Step 9.2: For the original waveform signal After performing the S-transform, the time-frequency characteristic equation The expression is: ； Where: t is time; It is a time index; f is the frequency; It is a Gaussian function, and its width is determined by the frequency f; Step 9.3: Obtain the time-frequency matrix based on amplitude and phase characteristics, including: According to the time-frequency characteristic equation By using the discrete S-transform formula, the complex values ​​at each time point τ and each frequency point f are calculated to form a time-domain matrix. ; Calculate the time-frequency matrix The modulus value in the middle is obtained ; Obtain time-frequency feature values, where the amplitude feature is: Phase characteristics are ; Step 9.4: For the original waveform signal After S-transformation, a new [structure] is formed. Waveform data, based on the playback function, enables high-speed and efficient playback of transient data.

10. The test method for a transient grounding protection test device for a distribution network according to claim 2, characterized in that: The waveform analysis program built into the waveform self-test module is used to execute a dual-certification automatic test method based on waveform playback, including: Step 10.1: After loading the original transient waveform, extract the signal to form the original data. ; Step 10.2: Forming the time-domain matrix after S-transformation And extract amplitude and phase features; Step 10.3: Based on the time-domain matrix dataset Perform waveform playback and simultaneously record the output waveform to form a new time-domain matrix. ; Step 10.4: First round of authentication, comparing and replaying waveform data. Waveform data acquired by recording If they are consistent, it means there is no problem with the playback system; if they are inconsistent, it means there is an anomaly in the playback system, and the relevant judgment ends. Step 10.5: After the first round of certification is successful, the second round of testing and certification will be conducted. The test will be judged as qualified based on whether the automatic test model and the collected protection output switch positions are consistent. If the protection output positions are consistent, the test will be judged as qualified; otherwise, the test will be judged as failed. Step 10.6: Summarize the overall test results to generate a test report, and end the overall process.

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