Current differential protection method and apparatus for power distribution network, and electronic device and storage medium
By performing feature analysis on the electrical signals of faulty sections of the distribution network, obtaining frequency and negative sequence current parameters, determining the fault type, and setting differential protection parameters, the problem of low efficiency of current differential protection in the distribution network is solved, more accurate fault identification and location are achieved, and the safety and reliability of the power grid are improved.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- GUANGDONG POWER GRID CO LTD
- Filing Date
- 2024-12-09
- Publication Date
- 2026-06-18
Smart Images
Figure CN2024137885_18062026_PF_FP_ABST
Abstract
Description
Current differential protection methods, devices, electronic equipment and storage media for power distribution networks Technical Field
[0001] This disclosure relates to the field of distribution network protection, and more specifically, to a current differential protection method, device, electronic equipment, and storage medium for distribution networks. Background Technology
[0002] The large-scale integration of distributed generation into distribution networks has transformed traditional single-source radial networks into complex multi-source power supply networks, leading to a continuous increase in distributed generation penetration. Distributed generation is typically affected by natural factors, resulting in intermittent and fluctuating output. In active distribution networks, both power flows and loads can exhibit bidirectional flow, and their behavior is uncertain. This leads to varying fault response characteristics within the distribution network, further complicating protection setups. Protection coordination becomes more difficult, posing new challenges to the selection and operating speed of protection schemes. Since active distribution network segments contain both source and load branches, the magnitude and phase of fault currents are influenced by loads and distributed generation branches, and branch loads may be unmeasurable. When a fault occurs downstream of a distributed generation source with a low fault current contribution, a significant "weak feed" phenomenon may occur. Therefore, directly applying current differential protection in such cases leads to lower reliability, necessitating improvements to existing protection schemes.
[0003] Differential current protection can compare the differential current using either the total current or the fault component current. Due to the nonlinear characteristics of intermittent distributed generation fault output, the fault component characteristics can differ significantly depending on the distributed generator's penetration rate, grid connection location, and fault location, leading to unreliable operation of the differential current protection. Furthermore, phase differential protection requires relatively large amounts of information, increasing the communication burden on the distribution network's communication channels. Related technologies typically consider using differential current protection based on positive-sequence fault components. Introducing differential protection based on positive-sequence fault components into active distribution networks eliminates the need for voltage information, can reflect all fault types, effectively adapts to multi-segment and multi-branch structures of the distribution network, and solves the problem of weak feeders. However, the comparison of positive-sequence fault components is significantly affected by the output characteristics of distributed generators, resulting in poor protection reliability. In summary, this leads to low efficiency in differential current protection for distribution networks in related technologies.
[0004] There is currently no effective solution to the above problems. Summary of the Invention
[0005] This disclosure provides a method, apparatus, electronic device, and storage medium for differential current protection of a distribution network, to at least solve the technical problem of low efficiency in differential current protection of distribution networks in related technologies.
[0006] According to one aspect of the present disclosure, a current differential protection method for a distribution network is provided, comprising: acquiring electrical signals at both ends of a faulty section in the distribution network when a fault occurs; performing feature analysis on the electrical signals to obtain feature analysis results, wherein the feature analysis results include at least frequency parameters and negative sequence current parameters of the electrical signals; determining the fault type of the faulty section based on the feature analysis results; and determining corresponding differential protection parameters based on the fault type to perform current differential protection on the distribution network.
[0007] According to another aspect of the embodiments of this disclosure, a current differential protection device for a distribution network is also provided, comprising: an acquisition module configured to acquire electrical signals at both ends of a faulty section in the distribution network when a fault occurs; an analysis module configured to perform feature analysis on the electrical signals to obtain feature analysis results, wherein the feature analysis results include at least frequency parameters and negative sequence current parameters of the electrical signals; a determination module configured to determine the fault type of the faulty section based on the feature analysis results; and a protection module configured to determine corresponding differential protection parameters based on the fault type and perform current differential protection on the distribution network.
[0008] According to another aspect of the present disclosure, an electronic device is also provided, including: a memory storing an executable program; and a processor for running the program, wherein the program executes the methods in various embodiments of the present disclosure when it runs.
[0009] According to another aspect of the embodiments of the present disclosure, a computer-readable storage medium is also provided, the computer-readable storage medium including a stored executable program, wherein, when the executable program is executed, it controls the device where the computer-readable storage medium is located to perform the methods of the various embodiments of the present disclosure.
[0010] According to another aspect of the embodiments of this disclosure, a computer program product is also provided, including a computer program that, when executed by a processor, implements the methods of various embodiments of this disclosure.
[0011] According to another aspect of the embodiments of this disclosure, a computer program product is also provided, including a non-volatile computer-readable storage medium storing a computer program that, when executed by a processor, implements the methods in various embodiments of this disclosure.
[0012] According to another aspect of the embodiments of this disclosure, a computer program is also provided, which, when executed by a processor, implements the methods of the various embodiments of this disclosure.
[0013] This disclosure provides a current differential protection method for a distribution network, comprising: acquiring electrical signals at both ends of a faulty section in the distribution network when a fault occurs; performing feature analysis on the electrical signals to obtain feature analysis results, wherein the feature analysis results include at least frequency parameters and negative sequence current parameters of the electrical signals; determining the fault type of the faulty section based on the feature analysis results; and determining corresponding differential protection parameters based on the fault type to perform current differential protection on the distribution network. It is noteworthy that this disclosure, by performing feature analysis on the electrical signals, can obtain feature analysis results including frequency parameters and negative sequence current parameters. Frequency parameters can help determine the fundamental frequency of the current, thereby identifying whether a fault or abnormal situation exists. Negative sequence current parameters can be used to detect asymmetrical faults in the power grid. These feature analysis results can provide more detailed and in-depth information about the current data, helping the differential protection device to accurately judge the fault situation in the power grid and respond promptly. Combining the above feature analysis results, the fault type of the faulty section can be determined more accurately, providing an accurate basis for subsequent protection actions. Furthermore, determining corresponding differential protection parameters according to different fault types can more accurately identify and locate faults, reducing the occurrence of false and missed actions. By rationally setting differential protection parameters, the number of malfunctions and missed operations can be reduced, maintenance costs and manual maintenance workload can be decreased, the safety and reliability of the power grid can be improved, and the impact of faults on the system can be reduced. This solves the technical problem of low efficiency in current differential protection of distribution networks in related technologies. Attached Figure Description
[0014] The accompanying drawings, which are included to provide a further understanding of this disclosure and form part of this disclosure, illustrate exemplary embodiments of the present disclosure and are used to explain the disclosure, but do not constitute an undue limitation of the disclosure. In the drawings:
[0015] Figure 1 is a flowchart of a current differential protection method for a distribution network according to an embodiment of the present disclosure. Detailed Implementation
[0016] To enable those skilled in the art to better understand the present disclosure, the technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present disclosure.
[0017] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0018] According to an embodiment of the present disclosure, an embodiment of a current differential protection method for a distribution network is provided. It can be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.
[0019] Figure 1 is a flowchart of a current differential protection method for a distribution network according to an embodiment of the present disclosure. As shown in Figure 1, the method includes the following steps:
[0020] Step S102: In the event of a fault in the distribution network, acquire the electrical signals at both ends of the faulty section in the distribution network.
[0021] In one optional embodiment, when a fault occurs in the distribution network, the electrical signals at both ends of the faulty section can be acquired first. Specifically, current transformers can be installed in the distribution network for real-time monitoring of current signals. When a fault occurs, the current transformers can detect abnormal current values. The current signal data collected by the current transformers can be acquired through a data acquisition system. The data acquisition system can transmit the signals to a remote monitoring center or protection equipment. The acquired current signal data can be processed and analyzed at the remote monitoring center or protection equipment. By comparing the current signals at both ends of the faulty section, the fault location and type can be determined. Through the above steps, real-time monitoring and analysis of current signals provide data basis and support for subsequent current differential protection of the distribution network.
[0022] Step S104: Perform feature analysis on the electrical signal to obtain the feature analysis results.
[0023] The feature analysis results include at least the frequency parameters and negative sequence current parameters of the electrical signal.
[0024] In one optional embodiment, feature analysis can be performed on the electrical signal. Specifically, corresponding current data can be collected. The differential protection device can acquire current data from different parts of the distribution network through a current transformer and convert it into a digital signal for subsequent processing and analysis. Then, feature analysis can be performed on the collected electrical signal data. Frequency parameters can be obtained using methods such as Fourier transform to acquire the frequency components of the electrical signal. Frequency parameters can help determine the fundamental frequency of the current, thereby identifying whether a fault or abnormal situation exists. Negative sequence current parameters can be used to detect asymmetrical faults in the power grid; that is, the presence of negative sequence current indicates an asymmetrical current distribution, possibly caused by a ground fault or ground current imbalance. By performing feature analysis on the electrical signal, feature analysis results, including frequency parameters and negative sequence current parameters, can be obtained. These feature analysis results can provide more detailed and in-depth information about the current data, helping the differential protection device accurately determine the fault situation in the power grid and respond promptly. Meanwhile, by monitoring and analyzing the results of feature analysis, we can also help predict potential fault risks, carry out preventive maintenance in advance, effectively reduce the accident rate, and improve the reliability and stability of the power grid. By analyzing features such as frequency parameters and negative sequence current parameters, we can gain a more comprehensive understanding of the characteristics of current data, providing more effective protection measures and decision-making basis for differential protection.
[0025] Step S106: Based on the feature analysis results, determine the fault type of the faulty section.
[0026] In one optional embodiment, determining the fault type of the faulty section helps engineers quickly locate and resolve the fault, thereby ensuring the safe and stable operation of the power grid. The fault type of the faulty section is determined based on feature analysis results, which include frequency parameters and negative-sequence current parameters of the electrical signal. Specifically, the frequency parameters of the electrical signal can be analyzed. Current can be affected by different frequency components during transmission, and different types of faults can cause changes in specific frequency components of the current signal. By performing spectral analysis on the current signal, the characteristics of different frequency components can be extracted, thereby determining the fault type. For example, short-circuit faults typically cause an increase in high-frequency components, while grounding faults can lead to an increase in low-frequency components. The negative-sequence current parameter can also be analyzed. In a power grid, the negative-sequence current component is normally very small, but a fault can cause an abnormal increase in the negative-sequence current. By monitoring and analyzing the negative-sequence current component, the fault type can be determined. For example, symmetrical faults typically lead to an increase in negative-sequence current, while asymmetrical faults can cause asymmetry in the negative-sequence current. Combining the analysis results of these two parameters allows for a more accurate determination of the fault type of the faulty section, providing an accurate basis for subsequent protection actions. This method can improve the accuracy and speed of fault diagnosis, helping to take timely measures to prevent the escalation of accidents and their impact on the stable operation of the entire power grid.
[0027] Step S108: Determine the corresponding differential protection parameters based on the fault type, and perform current differential protection on the distribution network.
[0028] In one optional embodiment, the corresponding differential protection parameters can be determined based on the fault type. Specifically, firstly, various fault types that may occur in the distribution network can be classified and analyzed. Fault types may include line short circuits, ground faults, overloads, etc. The current differences caused by different fault types may also vary. Next, corresponding differential protection parameters can be determined according to different fault types. These parameters may include protection range, operating sensitivity, and operating time. By analyzing the current characteristics of different fault types, suitable differential protection parameters can be determined to ensure timely and accurate protection action when a fault occurs. Then, the determined differential protection parameters can be configured into the differential protection equipment of the distribution network. These devices may include differential protection relays, transmitters, etc. After the parameters are configured, the system can monitor current differences in real time and trigger protection action when an abnormality is detected. Finally, the parameters can be debugged and optimized. In actual operation, some malfunctions or missed actions may occur. The protection parameters can be adjusted according to the actual situation to improve the accuracy and reliability of differential protection. By following the steps above and determining the corresponding differential protection parameters according to different fault types, faults can be identified and located more accurately, reducing malfunctions and missed trips. By setting the differential protection parameters appropriately, the number of malfunctions and missed trips can be reduced, maintenance costs and manual maintenance workload can be lowered, the safety and reliability of the power grid can be improved, and the impact of faults on the system can be reduced.
[0029] This disclosure provides a current differential protection method for a distribution network, comprising: acquiring electrical signals at both ends of a faulty section in the distribution network when a fault occurs; performing feature analysis on the electrical signals to obtain feature analysis results, wherein the feature analysis results include at least frequency parameters and negative sequence current parameters of the electrical signals; determining the fault type of the faulty section based on the feature analysis results; and determining corresponding differential protection parameters based on the fault type to perform current differential protection on the distribution network. It is noteworthy that this disclosure, by performing feature analysis on the electrical signals, can obtain feature analysis results including frequency parameters and negative sequence current parameters. Frequency parameters can help determine the fundamental frequency of the current, thereby identifying whether a fault or abnormal situation exists. Negative sequence current parameters can be used to detect asymmetrical faults in the power grid. These feature analysis results can provide more detailed and in-depth information about the current data, helping the differential protection device to accurately judge the fault situation in the power grid and respond promptly. Combining the above feature analysis results, the fault type of the faulty section can be determined more accurately, providing an accurate basis for subsequent protection actions. Furthermore, determining corresponding differential protection parameters according to different fault types can more accurately identify and locate faults, reducing the occurrence of false and missed actions. By rationally setting differential protection parameters, the number of malfunctions and missed operations can be reduced, maintenance costs and manual maintenance workload can be decreased, the safety and reliability of the power grid can be improved, and the impact of faults on the system can be reduced. This solves the technical problem of low efficiency in current differential protection of distribution networks in related technologies.
[0030] Optionally, feature analysis is performed on the electrical signal to obtain feature analysis results, including: frequency change analysis of the electrical signal to obtain frequency parameters, wherein the frequency parameters are used to characterize the frequency change rate of the electrical signal; and negative sequence current condition analysis of the electrical signal to obtain negative sequence current parameters, wherein the negative sequence current parameters are determined based on the negative sequence current and positive sequence current in the electrical signal.
[0031] In one optional embodiment, the specific implementation process of characteristic analysis of electrical signals may include frequency change analysis and negative sequence current condition analysis of the electrical signals. Specifically, firstly, frequency change analysis can be performed on the electrical signals. The frequency change of the electrical signal can reflect the rate of change of the current, and the frequency parameter can better characterize the characteristics of the electrical signal. Specifically, signal processing technology can be used to perform spectrum analysis on the acquired current signal to obtain the frequency distribution of the signal. The frequency parameter can be used to represent the rate of change of the current signal's frequency, thereby helping to determine whether there is an anomaly in the current. Secondly, negative sequence current condition analysis can be performed on the electrical signals. Negative sequence current refers to the current component in three-phase current that is 120 degrees out of phase with the positive sequence current. The presence of negative sequence current is often related to faults in the power grid, so analyzing negative sequence current can help detect faults in a timely manner. Specifically, the negative sequence current is separated from the positive sequence current through filtering technology, and then the negative sequence current parameters, including amplitude and phase information, are calculated. In the above steps, by performing characteristic analysis on the electrical signals, a more comprehensive understanding of the current changes can be obtained, thereby improving the sensitivity and accuracy of protection and reducing the occurrence of false trips. Frequency variation analysis and negative sequence current condition analysis can help distinguish between normal operating conditions and fault conditions, thus speeding up fault location and handling.
[0032] Optionally, the negative sequence current condition analysis of the electrical signal is performed to obtain the negative sequence current parameters, including: determining the negative sequence current parameters based on the ratio of negative sequence current to positive sequence current in the electrical signal.
[0033] In one optional embodiment, the current signal in the system is first acquired using a current sensor, sampled, and digitized to obtain raw electrical signal data. Then, negative-sequence analysis is performed on the raw electrical signal data, decomposing the current signal into positive-sequence and negative-sequence components using mathematical algorithms and digital signal processing techniques. The negative-sequence current can be caused by an asymmetrical system, indicating a fault or abnormal condition in the system. Next, the negative-sequence current parameter can be determined based on the ratio of the negative-sequence current to the positive-sequence current in the electrical signal. By comparing the magnitude and phase difference between the negative-sequence current and the positive-sequence current, the type and location of the fault in the system can be determined, thereby triggering protection actions. Finally, the protection action can be set based on the negative-sequence current parameter. When a fault occurs in the system, the current differential protection can promptly and accurately locate and isolate the fault, ensuring the safe and stable operation of the power system. In the above process, by analyzing the negative-sequence current status of the electrical signal, the fault situation in the system can be detected more accurately, avoiding false and missed actions, and improving the reliability of the protection system. The negative-sequence current parameter can help to quickly and accurately locate the fault point in the system, shorten the fault handling time, and reduce the impact of the fault on the system.
[0034] Optionally, based on the feature analysis results, the fault type of the fault section is determined, including: comparing the frequency parameter in the feature analysis results with a first preset threshold; if the frequency parameter is greater than or equal to the first preset threshold, the fault type is determined to be a three-phase short-circuit fault; if the frequency parameter is less than the first preset threshold, the negative sequence current parameter is compared with a second preset threshold to determine the fault type.
[0035] The aforementioned first preset threshold can refer to a pre-set value used to determine the frequency parameter, which can be 1, etc. The first preset threshold can be determined according to actual needs, and is not limited here.
[0036] The aforementioned second preset threshold can refer to a pre-set value used to determine the negative sequence current parameter, such as 0.5. The second preset threshold can be determined according to actual needs, and is not limited here.
[0037] In one optional embodiment, feature analysis is first performed to acquire the current signal collected by the current differential protection device, and frequency domain analysis is performed on the signal to extract frequency parameters. By comparing the frequency parameters with a first preset threshold, it is determined whether a fault has occurred. If the frequency parameter is greater than or equal to the first preset threshold, it is determined to be a three-phase short-circuit fault; if the frequency parameter is less than the first preset threshold, the next step is performed. Next, the negative sequence current parameter is compared with a second preset threshold. Negative sequence current can refer to the current generated under three-phase unbalanced conditions, which can be caused by a fault. By comparing the negative sequence current parameter with the second preset threshold, the fault type can be determined. In the above process, by comprehensively considering the frequency parameter and the negative sequence current parameter, the fault type can be determined more accurately, avoiding misjudgment or missed judgment, and improving the accuracy of fault diagnosis. Setting preset thresholds for comparison can effectively reduce the false alarm rate, avoid misjudging as a fault under normal conditions, reduce interference with system operation, and effectively determine the fault type through feature analysis combined with the comparison of preset thresholds, thereby improving the fault diagnosis capability of the current differential protection system and ensuring the safe and stable operation of the distribution network.
[0038] Optionally, if the frequency parameter is less than a first preset threshold, the negative sequence current parameter is compared with a second preset threshold to determine the fault type, including: if the negative sequence current parameter is greater than or equal to the second preset threshold, the fault type is determined to be a two-phase interphase fault; if the negative sequence current parameter is less than the second preset threshold, the fault type is determined to be a target fault type, wherein the target fault type is used to characterize a three-phase short circuit with transition resistance occurring in the fault section.
[0039] In one optional embodiment, if the frequency parameter is less than a first preset threshold, the negative sequence current parameter can be compared with a second preset threshold to determine the specific fault type. Under normal circumstances, the negative sequence current should be close to zero. When a fault occurs, the negative sequence current can change significantly, which can help determine the fault type. When performing current differential protection, the negative sequence current parameter can be compared with the second preset threshold. If the negative sequence current parameter is greater than or equal to the second preset threshold, then the fault type can be determined to be a two-phase fault. In this case, a short circuit occurs between the two phases, and measures can be taken in time to repair it. If the negative sequence current parameter is less than the second preset threshold, then the fault type can be determined to be the target fault type, that is, a three-phase short circuit with transition resistance in the fault section. In the above process, by comparing the negative sequence current parameter and the preset threshold, the fault type can be determined more accurately, avoiding misjudgment or omission. Timely and accurate determination of the fault type can effectively protect the equipment and system of the distribution network and improve its reliability and stability.
[0040] Optionally, the differential protection parameters include at least: protection starting current parameters, positive sequence ratio restraint coefficient, and negative sequence ratio restraint coefficient; determining the corresponding differential protection parameters based on the fault type and performing current differential protection on the distribution network includes: determining the corresponding protection starting current parameters, positive sequence ratio restraint coefficient, and negative sequence ratio restraint coefficient based on the fault type to obtain the differential protection parameters; and performing current differential protection on the distribution network based on the differential protection parameters and the preset differential protection action formula.
[0041] In one optional embodiment, the differential protection parameters may include protection initiation current parameters, positive-sequence ratio restraint coefficients, and negative-sequence ratio restraint coefficients. The protection initiation current parameter refers to the current value at which the differential protection system begins to operate when the current exceeds a certain threshold. The positive-sequence ratio restraint coefficients and negative-sequence ratio restraint coefficients are used to determine the proportional relationship between positive-sequence and negative-sequence currents in the differential protection system, respectively. In practical applications, corresponding differential protection parameters can be determined according to different fault types. For example, for line short-circuit faults, a lower initiation current parameter can be set to ensure rapid and accurate fault detection. For ground faults, different positive-sequence and negative-sequence ratio restraint coefficients can be determined according to the system grounding method to improve the accuracy of differential protection. By determining appropriate differential protection parameters, the distribution network system can be effectively protected from various faults. Based on the differential protection parameters and preset differential protection action formulas, current differential protection for the distribution network can be realized. When a fault occurs in the system, the differential protection system can determine the fault type and take corresponding protection measures according to the preset parameters and action formulas, thereby ensuring the safe and stable operation of the system. Optimizing differential protection parameter settings can reduce malfunctions and missed actions, improve the sensitivity and accuracy of the protection system, and provide effective protection for the operation of the distribution network system.
[0042] The technical solution proposed in this disclosure is described below with reference to an optional embodiment. This disclosure proposes a longitudinal protection scheme for a multi-point, highly integrated distribution network for distributed generation. By processing the fault characteristics of the fault section, the current vector information at both ends of the fault section is analyzed, and an action criterion based on an adaptive dual proportional braking coefficient is introduced. The adaptive criterion is adjusted according to different operating and fault conditions of the distribution network, thereby developing an adaptive proportional braking current differential protection scheme.
[0043] This disclosure proposes a current differential protection algorithm based on adaptive ratio. For the current detected at both ends of the segment, the frequency change is first analyzed. When the frequency change rate detected at one end of the protection is... In other words, when the frequency parameter exceeds the system disturbance threshold of 1 Hz / s, a three-phase short-circuit fault is likely to have occurred in that section. When a three-phase short circuit with transition resistance occurs in the section, the rate of change of the frequency of the current at both ends can be less than 1 Hz / s, which is the target fault type. When an asymmetrical fault occurs in an active distribution network, the system will exhibit negative sequence current. Theoretically, the negative sequence current is almost equal to the positive sequence current. However, considering the three-phase imbalance and measurement errors during normal operation, a margin is introduced. The ratio of the negative sequence current to the positive sequence current is defined as ε. If ε is greater than or equal to 0.5, an asymmetrical fault, i.e., a two-phase fault, is determined to have occurred.
[0044] Therefore, the differential protection parameters can be adaptively adjusted based on the frequency change rate and negative sequence current. The general operating criterion for adaptive differential protection, i.e., the preset differential protection operating relationship, can be expressed as:
[0045] In the formula, and This indicates the measured current at both ends of the segment; and This represents the positive sequence component of the current at both ends; and I represents the negative sequence component of the current at both ends; op To protect the starting current, i.e., to protect the starting current parameters; K1 is the positive sequence ratio braking coefficient; K2 is the negative sequence ratio braking coefficient. Therefore, based on the analysis of current vector information, the starting current and ratio braking coefficient can be dynamically adjusted in real time.
[0046] when When neither ε≥0.5 is satisfied, it indicates that no fault has occurred in the section or a three-phase short circuit with transition resistance has occurred, which can be the target fault type. In this case, the protection starting current is set to the maximum value of the difference between the output current of the distributed power source and the load current in the section, i.e., K1=0.5, K2=0. Thus, the following formula can be obtained to perform current differential protection on the distribution network under the target fault type.
[0047] when When this condition is met, it indicates that a three-phase short circuit may have occurred in the segment, i.e., a three-phase short circuit fault. In this case, K1 = 0.1, K2 = 0, and the protection starting current can be set to the maximum unbalanced current during the external fault, i.e., I. op =I unb.max Thus, the following formula can be obtained for current differential protection of the distribution network under three-phase short-circuit fault.
[0048] when When ε≥0.5 is satisfied, i.e., a two-phase interphase fault occurs; the protection starting current is set to the maximum unbalanced negative sequence current during the external fault, i.e., I. op =I unb.max(2) By setting K1=0 and K2=0.5, the following formula can be obtained for current differential protection of the distribution network under two-phase-to-phase faults.
[0049] During the execution of the protection procedure, if any action criterion is met, it indicates that a fault has occurred within the segment, and the protection immediately takes action to isolate the fault. If no criterion is met, the protection can immediately return to reset.
[0050] This disclosure addresses the challenges of active distribution networks with multiple distributed generation (DG) connection points, taking into account the low-voltage ride-through characteristics of DG, transition resistance, and the effects of load. It utilizes the different characteristics of current frequency (which remains almost constant during normal operation, with no negative sequence component) and the differences in positive and negative sequence components and frequencies of the current vectors at the fault and non-faulty ends during three-phase and two-phase short circuits to adjust the adaptive setting values of the protection criterion. A dual-proportional braking coefficient adaptive current differential protection scheme for active distribution networks is proposed. Theoretical analysis and simulation results show that the proposed protection scheme operates reliably under various scenarios, including different DG penetration rates, grid connection points, fault types, fault locations, and weak feeder conditions, while also demonstrating tolerance to transition resistance.
[0051] According to another aspect of the embodiments of this disclosure, a current differential protection device for a distribution network is also provided, comprising: an acquisition module configured to acquire electrical signals at both ends of a faulty section in the distribution network when a fault occurs; an analysis module configured to perform feature analysis on the electrical signals to obtain feature analysis results, wherein the feature analysis results include at least frequency parameters and negative sequence current parameters of the electrical signals; a determination module configured to determine the fault type of the faulty section based on the feature analysis results; and a protection module configured to determine corresponding differential protection parameters based on the fault type and perform current differential protection on the distribution network.
[0052] The analysis module is also configured to perform frequency change analysis on the electrical signal to obtain frequency parameters, which are used to characterize the frequency change rate of the electrical signal; and to perform negative sequence current analysis on the electrical signal to obtain negative sequence current parameters, which are determined based on the negative sequence current and positive sequence current in the electrical signal.
[0053] The analysis module is also configured to determine the negative sequence current parameters based on the ratio of negative sequence current to positive sequence current in the electrical signal.
[0054] The determination module is further configured to compare the frequency parameter in the feature analysis results with a first preset threshold. If the frequency parameter is greater than or equal to the first preset threshold, the fault type is determined to be a three-phase short-circuit fault. If the frequency parameter is less than the first preset threshold, the negative sequence current parameter is compared with a second preset threshold to determine the fault type.
[0055] The determination module is further configured to determine the fault type as a two-phase interphase fault when the negative sequence current parameter is greater than or equal to a second preset threshold; and to determine the fault type as a target fault type when the negative sequence current parameter is less than the second preset threshold. The target fault type is used to characterize a three-phase short circuit with transition resistance occurring in the fault section.
[0056] The differential protection parameters include at least: protection starting current parameters, positive sequence ratio braking coefficient, and negative sequence ratio braking coefficient; the protection module is also configured to determine the corresponding protection starting current parameters, positive sequence ratio braking coefficient, and negative sequence ratio braking coefficient based on the fault type to obtain the differential protection parameters; and based on the differential protection parameters and the preset differential protection action formula, current differential protection is performed on the distribution network.
[0057] Embodiments of this disclosure also provide an electronic device, including: a memory storing an executable program; and a processor for running the program, wherein the program executes the methods described in various embodiments of this disclosure when it runs.
[0058] The aforementioned memory can refer to devices inside a computer used to store data and programs, including RAM, hard disks, etc. RAM can be used to temporarily store running programs and data, while hard disks can be used to store programs and data long-term. Memory enables the computer to read and write data and execute programs. The aforementioned processor is responsible for executing instructions in computer programs and performing data processing. It can also be responsible for controlling and executing various operations, including arithmetic operations, logical operations, and data transmission.
[0059] Embodiments of this disclosure also provide a computer-readable storage medium including a stored executable program, wherein, when the executable program is executed, it controls the device on which the computer-readable storage medium resides to perform the methods of the various embodiments of this disclosure.
[0060] The aforementioned computer storage media can refer to the media used in computer memory to store certain discontinuous physical quantities. Computer storage media mainly include semiconductors, magnetic cores, magnetic drums, magnetic tapes, laser discs, etc. Computer-readable storage media include stored programs, which can be a set of instructions that a computer can recognize and execute, running on an electronic computer to meet certain information needs.
[0061] Embodiments of this disclosure also provide a computer program product, including a computer program that, when executed by a processor, implements the methods of various embodiments of this disclosure.
[0062] The aforementioned computer program products can refer to software programs that have been written, tested, and released, and can run on computers or other devices. Computer program products can include application programs, operating systems, utility software, etc., used to achieve specific functions or solve specific problems.
[0063] Embodiments of this disclosure also provide a computer program product, including a non-volatile computer-readable storage medium for storing a computer program that, when executed by a processor, implements the methods described in various embodiments of this disclosure.
[0064] The aforementioned non-volatile computer-readable storage medium can refer to a medium for storing data. Non-volatile computer-readable storage media can retain data without loss when power is off and can be used to store long-term data, such as operating systems, applications, and user files. Non-volatile storage media can include hard disk drives, solid-state drives, optical disks, and flash memory storage devices, etc.
[0065] Embodiments of this disclosure also provide a computer program that, when executed by a processor, implements the methods described in the various embodiments of this disclosure.
[0066] The aforementioned computer program can refer to a set of instructions used to tell the computer to perform specific tasks or operations. Computer programs can be written by programmers using specific programming languages and can include algorithms, data structures, logic, and control flow. Computer programs can be used for a variety of purposes, including application software, operating systems, etc.
[0067] In the above embodiments of this disclosure, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.
[0068] In the several embodiments provided in this disclosure, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between units or modules may be electrical or other forms.
[0069] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.
[0070] Furthermore, the functional units in the various embodiments of this disclosure can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.
[0071] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this disclosure, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this disclosure. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard drive, magnetic disk, or optical disk.
[0072] The above description is only a preferred embodiment of this disclosure. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principles of this disclosure, and these improvements and modifications should also be considered within the scope of protection of this disclosure. Industrial applicability
[0073] This disclosure, through feature analysis of electrical signals, yields characteristic analysis results including frequency parameters and negative sequence current parameters. Frequency parameters help determine the fundamental frequency of the current, thereby identifying the presence of faults or anomalies. Negative sequence current parameters can be used to detect asymmetrical faults in the power grid. These feature analysis results provide more detailed and in-depth information about the current data, helping differential protection devices accurately determine fault conditions in the power grid and respond promptly. By combining the above feature analysis results, the fault type of the faulty section can be more accurately determined, providing an accurate basis for subsequent protection actions. Furthermore, determining the corresponding differential protection parameters based on different fault types allows for more precise fault identification and location, reducing the occurrence of false and missed actions. By rationally setting differential protection parameters, the number of false and missed actions can be reduced, maintenance costs and manual maintenance workload can be lowered, and the safety and reliability of the power grid can be improved, reducing the impact of faults on the system. This solves the technical problem of low efficiency in current differential protection of distribution networks in related technologies.
Claims
1. A current differential protection method for a distribution network, comprising: In the event of a fault in the distribution network, acquire the electrical signals at both ends of the faulty section in the distribution network; The electrical signal is subjected to feature analysis to obtain feature analysis results, wherein the feature analysis results include at least the frequency parameter and negative sequence current parameter of the electrical signal; Based on the feature analysis results, the fault type of the faulty section is determined; Based on the fault type, the corresponding differential protection parameters are determined, and current differential protection is performed on the distribution network.
2. The current differential protection method for distribution networks according to claim 1, wherein, The electrical signal is subjected to feature analysis to obtain feature analysis results, including: The frequency change of the electrical signal is analyzed to obtain the frequency parameters, wherein the frequency parameters are used to characterize the rate of change of the frequency of the electrical signal; The negative sequence current condition is analyzed on the electrical signal to obtain the negative sequence current parameters, wherein the negative sequence current parameters are determined based on the negative sequence current and positive sequence current in the electrical signal.
3. The current differential protection method for distribution networks according to claim 2, wherein, The negative sequence current condition is analyzed on the electrical signal to obtain the negative sequence current parameters, including: The negative sequence current parameter is determined based on the ratio of the negative sequence current to the positive sequence current in the electrical signal.
4. The current differential protection method for distribution networks according to claim 1, wherein, Based on the feature analysis results, the fault type of the faulty section is determined, including: The frequency parameter in the feature analysis result is compared with a first preset threshold. If the frequency parameter is greater than or equal to the first preset threshold, the fault type is determined to be a three-phase short circuit fault. If the frequency parameter is less than the first preset threshold, the negative sequence current parameter is compared with the second preset threshold to determine the fault type.
5. The current differential protection method for distribution networks according to claim 4, wherein, When the frequency parameter is less than the first preset threshold, the negative sequence current parameter is compared with a second preset threshold to determine the fault type, including: If the negative sequence current parameter is greater than or equal to the second preset threshold, the fault type is determined to be a two-phase interphase fault. When the negative sequence current parameter is less than the second preset threshold, the fault type is determined as the target fault type, wherein the target fault type is used to characterize the occurrence of a three-phase short circuit with transition resistance in the fault section.
6. The current differential protection method for distribution networks according to claim 1, wherein, The differential protection parameters include at least: protection starting current parameters, positive sequence ratio restraint coefficient, and negative sequence ratio restraint coefficient; based on the fault type, the corresponding differential protection parameters are determined to perform current differential protection on the distribution network, including: Based on the fault type, the corresponding protection starting current parameters, positive sequence ratio braking coefficient, and negative sequence ratio braking coefficient are determined to obtain the differential protection parameters. Based on the differential protection parameters and the preset differential protection action formula, current differential protection is performed on the distribution network.
7. A current differential protection device for a power distribution network, comprising: The acquisition module is configured to acquire electrical signals at both ends of the faulty section in the distribution network in the event of a fault in the distribution network. The analysis module is configured to perform feature analysis on the electrical signal to obtain feature analysis results, wherein the feature analysis results include at least the frequency parameter and negative sequence current parameter of the electrical signal; The determination module is configured to determine the fault type of the faulty section based on the feature analysis results; The protection module is configured to determine the corresponding differential protection parameters based on the fault type and perform current differential protection on the distribution network.
8. The current differential protection device for a power distribution network according to claim 7, wherein, The analysis module is further configured to perform frequency change analysis on the electrical signal to obtain the frequency parameter, wherein the frequency parameter is used to characterize the frequency change rate of the electrical signal; and to perform negative sequence current condition analysis on the electrical signal to obtain the negative sequence current parameter, wherein the negative sequence current parameter is determined based on the negative sequence current and positive sequence current in the electrical signal.
9. The current differential protection device for a power distribution network according to claim 8, wherein, The analysis module is further configured to determine the negative sequence current parameter based on the ratio of the negative sequence current to the positive sequence current in the electrical signal.
10. The current differential protection device for a power distribution network according to claim 7, wherein, The determining module is further configured to compare the frequency parameter in the feature analysis result with a first preset threshold, and if the frequency parameter is greater than or equal to the first preset threshold, determine that the fault type is a three-phase short circuit fault. If the frequency parameter is less than the first preset threshold, the negative sequence current parameter is compared with the second preset threshold to determine the fault type.
11. The current differential protection method for a distribution network according to claim 10, wherein, The analysis module is further configured to determine the fault type as a two-phase interphase fault when the negative sequence current parameter is greater than or equal to the second preset threshold; and to determine the fault type as a target fault type when the negative sequence current parameter is less than the second preset threshold, wherein the target fault type is used to characterize a three-phase short circuit with transition resistance occurring in the fault section.
12. The current differential protection device for a distribution network according to claim 7, wherein, The differential protection parameters include at least: protection starting current parameters, positive sequence ratio braking coefficient, and negative sequence ratio braking coefficient; the protection module is also configured to determine the corresponding protection starting current parameters, positive sequence ratio braking coefficient, and negative sequence ratio braking coefficient based on the fault type to obtain the differential protection parameters; and to perform current differential protection on the distribution network based on the differential protection parameters and the preset differential protection action formula.
13. An electronic device, comprising: Memory, which stores executable programs; A processor for running the program, wherein the program executes the current differential protection method for a distribution network according to any one of claims 1 to 6.
14. A computer-readable storage medium comprising a stored executable program, wherein, When the executable program is running, it controls the device containing the storage medium to perform the current differential protection method for the power distribution network as described in any one of claims 1 to 6.
15. A computer program product comprising a computer program that, when executed by a processor, implements the current differential protection method for a distribution network according to any one of claims 1 to 6.