Zero-sequence CT polarity verification method, device, equipment, medium and product
By obtaining the zero-sequence voltage and current of the bus after the feeder protection of the distribution network trips, and calculating the phase difference using a fitting function, the problem of low accuracy of zero-sequence CT polarity verification is solved, achieving efficient and accurate polarity judgment, and ensuring the reliability of fault location and power supply stability.
Patent Information
- Application Number
- CN202511933482.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-19
- Publication Date
- 2026-03-17
AI Technical Summary
Existing zero-sequence CT polarity verification methods have low accuracy and rely on analog signals or externally injected signals, which leads to a disconnect from actual operating conditions and affects power supply reliability and operation and maintenance efficiency.
After the protection trips and the fault disappears in the distribution network feeder, the zero-sequence voltage and zero-sequence current of the bus are obtained, the amplitude and phase difference are calculated using a fitting function, and the polarity of the zero-sequence CT is determined by combining the preset phase difference range, thus avoiding reliance on analog signals or externally injected signals.
It improves the accuracy and adaptability of zero-sequence CT polarity verification, ensures the reliable operation of the fault location device, and reduces the impact of power outages and maintenance costs.
Smart Images
Figure CN121679458A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power system technology, and in particular to a zero-sequence CT polarity verification method, apparatus, equipment, medium and product. Background Technology
[0002] During the operation of a distribution network, conventional distribution network lines are equipped with zero-sequence current protection devices. After detecting an overcurrent signal through a zero-sequence current transformer (CT), the zero-sequence current protection device will trigger a trip to isolate the fault. However, if the polarity of the zero-sequence CT is reversed, it will cause the phase of the collected zero-sequence current to reverse, leading to misjudgment of the fault location. This will not only delay the fault isolation time but may even expand the power outage area and cause more serious power supply impact.
[0003] Currently, the mainstream verification methods fall into two categories: manual verification during power outages and live signal injection verification. Specifically, manual verification during power outages requires interrupting the power supply to the distribution network. Maintenance personnel then inject a simulated zero-sequence current signal into the primary side of the zero-sequence current transformer (CT) using a signal generator. The phase of the signal is then measured on the secondary side using a phase meter, and the polarity is determined by comparing the injected and measured phases. Live signal injection verification, on the other hand, requires injecting a zero-sequence signal of a specific frequency into the system while the distribution network is energized. The phase characteristics of the feedback signals from the secondary side of each zero-sequence CT are then detected to determine the polarity.
[0004] However, the accuracy of zero-sequence CT polarity verification in existing technologies is low. Summary of the Invention
[0005] This application provides a method, apparatus, device, medium, and product for zero-sequence CT polarity verification, which aims to improve the accuracy of zero-sequence CT polarity verification.
[0006] In a first aspect, embodiments of this application provide a zero-sequence CT polarity verification method, including:
[0007] If a feeder in the distribution network trips due to protection, and the fault in the feeder disappears after the protection trip, then the zero-sequence voltage of the bus of the distribution network and the zero-sequence current of the feeder within one cycle are obtained.
[0008] The amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current of the bus are calculated respectively using a pre-defined fitting function.
[0009] The phase difference between the zero-sequence voltage and the zero-sequence current of the busbar is determined based on the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current.
[0010] Based on the phase difference and the preset phase difference range, the polarity verification result of the zero-sequence CT of the feeder is determined.
[0011] In one possible implementation, determining the polarity verification result of the zero-sequence CT of the feeder based on the phase difference and a preset phase difference range includes:
[0012] If the phase difference is within the preset phase difference range, then the polarity verification result is determined to be that the zero-sequence CT does not have a polarity reversal fault;
[0013] Conversely, the polarity check result indicates that the zero-sequence CT has a polarity reverse connection fault.
[0014] In one possible implementation, the preset phase difference range is 90°-180°.
[0015] In one possible implementation, the fitting function is an n×2 matrix, where n is the number of sampling points, each row represents the signal component at a sampling time, the first column represents the sine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network, and the second column represents the cosine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network.
[0016] In one possible implementation, the step of calculating the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current of the bus using a pre-defined fitting function includes:
[0017] Through formula Calculate the amplitude of the zero-sequence voltage of the bus;
[0018] Through formula Calculate the amplitude of the zero-sequence current;
[0019] in, The amplitude of the zero-sequence voltage of the bus is given. The zero-sequence voltage of the bus is... The fitting function is... The amplitude of the zero-sequence current. The amplitude of the zero-sequence current is given.
[0020] In one possible implementation, determining the phase difference between the zero-sequence voltage and the zero-sequence current based on the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current includes:
[0021] Through formula Determine the phase difference between the zero-sequence voltage and the zero-sequence current of the bus;
[0022] in, The phase difference is mentioned.
[0023] In one possible implementation, the method further includes:
[0024] If the polarity check result indicates that the zero-sequence CT has a polarity reverse fault, the zero-sequence current of the feeder is reversed, and the value obtained by the operation is determined as the target zero-sequence current. The target zero-sequence current is used for subsequent fault selection operations.
[0025] Secondly, embodiments of this application provide a zero-sequence CT polarity verification device, comprising:
[0026] The acquisition module is used to acquire the zero-sequence voltage of the bus and the zero-sequence current of the feeder within one cycle if the feeder of the distribution network experiences a protection trip and the fault of the feeder disappears after the protection trip.
[0027] The calculation module is used to calculate the amplitude of the zero-sequence voltage of the bus and the amplitude of the zero-sequence current respectively using a pre-set fitting function;
[0028] The first determining module is used to determine the phase difference between the zero-sequence voltage and the zero-sequence current based on the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current.
[0029] The second determining module is used to determine the polarity verification result of the zero-sequence CT of the feeder based on the phase difference and the preset phase difference range.
[0030] In one possible implementation, the second determining module is specifically used for:
[0031] If the phase difference is within the preset phase difference range, then the polarity verification result is determined to be that the zero-sequence CT does not have a polarity reversal fault;
[0032] Conversely, the polarity check result indicates that the zero-sequence CT has a polarity reverse connection fault.
[0033] In one possible implementation, the preset phase difference range is 90°-180°.
[0034] In one possible implementation, the fitting function is an n×2 matrix, where n is the number of sampling points, each row represents the signal component at a sampling time, the first column represents the sine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network, and the second column represents the cosine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network.
[0035] In one possible implementation, the computing module is specifically used for:
[0036] Through formula Calculate the amplitude of the zero-sequence voltage of the bus;
[0037] Through formula Calculate the amplitude of the zero-sequence current;
[0038] in, The amplitude of the zero-sequence voltage of the bus is given. The zero-sequence voltage of the bus is... The fitting function is... The amplitude of the zero-sequence current. The amplitude of the zero-sequence current is given.
[0039] In one possible implementation, the first determining module is specifically used for:
[0040] Through formula Determine the phase difference between the zero-sequence voltage and the zero-sequence current of the bus;
[0041] in, The phase difference is mentioned.
[0042] In one possible implementation, the zero-sequence CT polarity verification device further includes a third module for:
[0043] If the polarity check result indicates that the zero-sequence CT has a polarity reverse fault, the zero-sequence current of the feeder is reversed, and the value obtained by the operation is determined as the target zero-sequence current. The target zero-sequence current is used for subsequent fault selection operations.
[0044] Thirdly, embodiments of this application provide an electronic device, including: a memory and a processor;
[0045] The memory stores computer-executed instructions;
[0046] The processor executes computer execution instructions stored in the memory, causing the processor to perform the first aspect and / or various possible implementations of the first aspect as described above.
[0047] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the first aspect and / or various possible implementations of the first aspect.
[0048] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the first aspect and / or various possible implementations of the first aspect.
[0049] The zero-sequence CT polarity verification method, apparatus, equipment, medium, and product provided in this application obtain the bus zero-sequence voltage and feeder zero-sequence current within one cycle after a protection trip occurs on a distribution network feeder and the fault disappears. The amplitude of these two voltages is calculated using a fitting function, and the phase difference is determined. The polarity verification result is then obtained by combining this with a preset phase difference range. This scheme does not rely on analog signals or externally injected signals; it directly utilizes electrical signals under actual operating conditions after a fault for verification. This avoids the impact of power outage verification on power supply reliability and solves the problems of high cost and susceptibility to interference in live-line injection verification. It significantly improves verification accuracy and adaptability, ensuring accurate zero-sequence CT polarity judgment results, providing core assurance for the reliable operation of fault location devices, and meeting the needs of efficient operation and maintenance of distribution networks. Attached Figure Description
[0050] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.
[0051] Figure 1 This application provides a low-resistance grounding system for power distribution networks.
[0052] Figure 2 Flowchart of the zero-sequence CT polarity verification method provided in this application Figure 1 ;
[0053] Figure 3 Flowchart of the zero-sequence CT polarity verification method provided in this application Figure 2 ;
[0054] Figure 4 A schematic diagram of the zero-sequence CT polarity verification device provided in this application;
[0055] Figure 5 A schematic diagram of the structure of the electronic device provided in this application.
[0056] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation
[0057] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.
[0058] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of the relevant data must comply with relevant laws, regulations and standards, and corresponding operation entry points are provided for users to choose to authorize or refuse.
[0059] First, the application scenarios involved in this application will be explained:
[0060] During the operation of a distribution network, conventional distribution network lines are equipped with zero-sequence current protection devices. When a single-phase ground fault occurs on a line, the system's zero-sequence current increases significantly. After detecting the overcurrent signal through a zero-sequence current transformer (CT), the zero-sequence current protection device will trigger a trip to isolate the fault. For zero-sequence current line protection devices, it is usually sufficient to obtain the amplitude information of the zero-sequence current to achieve the protection function; however, the fault location device in a substation is different. Its fault location criteria often require the phase information of the zero-sequence current. By comparing the phase difference between the zero-sequence voltage and the zero-sequence current of each line, the faulty line can be accurately located.
[0061] In practical applications, the zero-sequence voltage of the busbar is used as a reference. The faulty line is located by comparing the phase difference between the zero-sequence current of each feeder and the zero-sequence voltage of the busbar. The faulty line lags the zero-sequence voltage of the busbar by 90°~180°, while the non-faulty line leads the zero-sequence voltage of the busbar by about 90°. If the polarity of the zero-sequence current transformer (CT) is reversed, it will cause the phase of the acquired zero-sequence current to reverse, leading to misjudgment of the fault. This will not only delay the fault isolation time but may also expand the power outage area and cause more serious power supply impact.
[0062] Currently, the mainstream verification methods fall into two categories: one is manual verification during power outages, which requires interrupting the power supply to the distribution network. Maintenance personnel inject a simulated zero-sequence current signal into the primary side of the zero-sequence current transformer (CT) using a signal generator, and then measure the signal phase on the secondary side using a phase meter. The polarity is then determined by comparing the injected and measured phase relationships. This method not only affects power supply reliability and is inefficient, but the simulated signal cannot replicate the actual fault conditions, posing a risk of verification deviation. The other method is live signal injection verification, which requires injecting a specific frequency zero-sequence signal into the system while the distribution network is energized. This involves detecting the phase characteristics of the feedback signals from the secondary side of each zero-sequence CT to determine the polarity. While it does not require power outages, it requires specialized high-precision equipment, is costly, and is susceptible to interference from grid harmonics and load fluctuations. In complex distribution networks, there are also verification blind spots caused by signal attenuation.
[0063] However, the common problem with both methods is that they both rely on analog signals or externally injected signals, which leads to a disconnect from actual working conditions, low verification accuracy, and difficulty in meeting the needs of efficient operation and maintenance.
[0064] For low-resistance grounding systems, when a single-phase ground fault occurs, the phase difference between the zero-sequence voltage and zero-sequence current of the faulted line is different from that of the non-faulted line. Figure 1 The following analysis will be based on a small-resistance grounding system in the distribution network shown.
[0065] Figure 1 This application provides a low-resistance grounding system for a power distribution network. For example... Figure 1 As shown, the primary side of the 110kV / 10.5kV step-down transformer on the power supply side is connected in series with the upstream 110kV high-voltage AC power source, serving as the AC power source for the entire distribution network. The secondary side is connected in a star configuration to the 10kV busbar, where it is stepped down to the rated 10kV AC voltage of the distribution network, providing stable three-phase power frequency AC power to all subsequent branches. The 10kV busbar, as the power distribution and signal collection hub of the system, not only collects the input AC power and distributes it to each outgoing line, but also has a busbar voltage transformer (PT) connected in parallel. The primary winding of this busbar PT is connected across the three-phase conductors of the busbar and ground, without the need for current transmission circuitry, accurately acquiring the AC voltage signal of the busbar solely through parallel connection.
[0066] There are also three 10kV feeders directly connected to the busbar. The three feeders are connected in parallel to the busbar to form an independent AC power output channel, which can supply power to end users separately without interfering with each other. Each feeder has a corresponding zero-sequence current transformer connected in series in the primary side of the line. All AC current flowing through the feeder must pass completely through the primary winding of the zero-sequence current transformer to ensure that the zero-sequence current transformer can accurately sense and convert the AC zero-sequence current signal of the feeder.
[0067] The primary side of the grounding transformer is connected in a star configuration to the 10kV busbar, which can sense the AC zero-sequence voltage change of the busbar in real time and provide the necessary path to ground for the zero-sequence current; its secondary side is closely connected in series with the grounding resistor, and together they are connected to the ground.
[0068] The fault point K is located in the middle of feeder 3, connected in series in the conductor loop of feeder 3, simulating a single-phase ground fault scenario. After the fault occurs, the conductor of feeder 3 is connected to the ground through point K. For the faulty line (feeder 3), the zero-sequence current flows from the line to the busbar. For the non-faulty lines (feeders 1 and 2), the zero-sequence current flows from the busbar to the line. Furthermore, since the system is grounded through a small resistor, the zero-sequence current also flows from the busbar to the grounding resistor.
[0069] from Figure 1As can be seen from this, the relationship between zero-sequence currents can be expressed by the following formula:
[0070] I01+I02+I03+I0R=0
[0071] If the zero-sequence voltage U0 of the bus is used as the phase reference, then I01 and I02 lead by 90°, and I0R and U0 are in phase.
[0072] According to the above formula, I03 lags U0 by more than 90°, and the maximum lag is no more than 180°.
[0073] Based on the above technical issues and Figure 1 Analysis revealed that when a single-phase ground fault occurs in a line, the phase difference between the zero-sequence voltage and zero-sequence current of the faulty line differs from that of the non-faulty line. The technical concept of this application is as follows: During the research of zero-sequence CT polarity verification schemes, the inventors discovered that existing verification methods rely on analog signals or externally injected signals, resulting in a disconnect from actual operating conditions and low verification accuracy. Considering that when a distribution network feeder experiences a protection trip and the fault persists, the system generates bus voltage and zero-sequence current signals reflecting the actual operating conditions, which can be directly used as verification criteria, the bus voltage and feeder zero-sequence current within one cycle can be obtained. Their amplitudes are calculated using a pre-set fitting function, and the phase difference is determined based on the amplitude. Combining the phase difference with the pre-set phase difference range, the zero-sequence CT polarity verification result can be determined without externally injected signals. This zero-sequence CT polarity verification result conforms to actual operating conditions, effectively improving verification accuracy.
[0074] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.
[0075] Figure 2 Flowchart of the zero-sequence CT polarity verification method provided in this application Figure 1 ,like Figure 2 As shown, the method includes:
[0076] S21. If a feeder in the distribution network experiences a protection trip, and the fault in the feeder disappears after the protection trip, then obtain the zero-sequence voltage of the bus and the zero-sequence current of the feeder within one cycle.
[0077] In this step, when a single-phase ground fault occurs on the distribution network feeder, bus zero-sequence voltage and zero-sequence current signals that reflect the actual operating conditions will be generated. When the fault disappears after the protection trips, it indicates that the fault has been effectively isolated. The signals in this scenario can be directly used as the verification basis to provide accurate data support for subsequent polarity verification.
[0078] In distribution networks, feeders refer to power lines that extend from the distribution network busbar to transmit electrical energy to end users or branch lines, such as... Figure 1 The three feeders in the middle.
[0079] In practical applications, protection tripping refers to the action of the zero-sequence current protection device in the distribution network to disconnect the feeder circuit after detecting a zero-sequence overcurrent signal caused by a single-phase ground fault in the feeder. Its purpose is to isolate the faulty line and prevent the fault from escalating. After the protection trips, the single-phase ground fault in the feeder is completely isolated, and the distribution network returns to normal operation or a fault-free state. At this point, zero-sequence current transformer (CT) polarity verification is required.
[0080] For example, for a 50Hz power frequency distribution network, the corresponding period is 0.02 seconds. Selecting a signal within one period is to ensure that the acquired bus zero-sequence voltage and zero-sequence current signals are complete and continuous.
[0081] Among them, the bus zero-sequence voltage refers to the phasor sum of the three-phase voltages at the bus of the distribution network, which is obtained by the bus PT. The feeder zero-sequence current refers to the phasor sum of the three-phase currents flowing through the feeder, which is obtained by the zero-sequence CT connected in series in the feeder.
[0082] For example, the zero-sequence voltage of the bus and the zero-sequence current of the feeder can be expressed by the following formulas:
[0083]
[0084] in, This is the zero-sequence voltage of the bus. Let be the zero-sequence current of the feeder, and n be the number of sampling points in one cycle. , The sampling frequency.
[0085] S22. Calculate the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current of the bus using a pre-defined fitting function.
[0086] In this step, since S21 has acquired the bus zero-sequence voltage and feeder zero-sequence current signals within one cycle after the protection trip, these signals are periodic fluctuation signals. The amplitude needs to be extracted through a specific fitting method in order to further calculate the phase difference between the two.
[0087] Optionally, the fitting function is an n×2 matrix, where n is the number of sampling points. Each row represents the signal component at a sampling time. The first column contains the sine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network, and the second column contains the cosine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network.
[0088] Specifically, the above fitting function can be represented by the following formula:
[0089]
[0090] in, The power frequency is 50Hz. The sampling period is .
[0091] Since both the zero-sequence voltage and zero-sequence current of the bus are periodic signals of trigonometric functions, a fitting function composed of sine and cosine functions provides a stable and reliable benchmark tool for calculating the amplitude of the zero-sequence voltage and zero-sequence current of the bus. This ensures that the fitting process is standardized and the results are accurate, avoiding parameter extraction errors caused by unclear fitting functions. Simultaneously, this fitting function is highly compatible with the power frequency characteristics of the distribution network, accurately capturing the core features of periodic electrical signals, laying a solid data foundation for subsequent phase difference calculations, and ensuring the stability and accuracy of the entire verification process.
[0092] Based on this, through the formula Calculate the amplitude of the zero-sequence voltage at the bus, and use the formula... Calculate the amplitude of the zero-sequence current.
[0093] in, The amplitude of the zero-sequence voltage of the busbar. This is the zero-sequence voltage of the bus. For the fitting function, The amplitude of the zero-sequence current. The amplitude of the zero-sequence current.
[0094] Among them, the amplitude of the bus zero-sequence voltage refers to the amplitude parameters of the sine and cosine terms of the acquired bus zero-sequence voltage signal obtained by fitting the acquired signal with a pre-set fitting function. It is a core indicator reflecting the intensity of the bus zero-sequence voltage signal fluctuation. Similarly, the amplitude of the zero-sequence current refers to the amplitude parameters of the sine and cosine terms of the acquired feeder zero-sequence current signal obtained by fitting the acquired feeder zero-sequence current signal with a pre-set fitting function. It is a core indicator reflecting the intensity of the feeder zero-sequence current signal fluctuation.
[0095] S23. Determine the phase difference between the zero-sequence voltage and the zero-sequence current of the busbar based on the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current.
[0096] In this step, the phase difference between the zero-sequence voltage and the zero-sequence current of the bus is the core basis for determining whether the polarity of the zero-sequence CT is reversed. Therefore, it is necessary to derive the phase difference between the zero-sequence voltage and the zero-sequence current of the bus based on the two sets of extracted amplitude parameters.
[0097] The phase difference refers to the phase difference between the zero-sequence voltage of the bus and the zero-sequence current of the feeder during the periodic fluctuation process, with the zero-sequence voltage of the bus as the phase reference. Its value ranges from 0° to 360°.
[0098] In one possible implementation, through the formula Determine the phase difference between the zero-sequence voltage and zero-sequence current of the bus.
[0099] in, This represents the phase difference.
[0100] S24. Determine the polarity verification result of the zero-sequence CT of the feeder based on the phase difference and the preset phase difference range.
[0101] In this step, considering that in a low-resistance grounding system, the phase difference between the zero-sequence current of the fault line and the zero-sequence voltage of the busbar collected by the zero-sequence CT with normal polarity has a fixed range, by matching the calculated phase difference with this preset range, it can be determined whether the zero-sequence CT has a polarity reverse fault, thereby solving the problem of low accuracy of the existing verification method.
[0102] The preset phase difference range refers to the standard phase difference interval between the zero-sequence current of the faulty line and the zero-sequence voltage of the busbar when the polarity of the zero-sequence CT is correct in a low-resistance grounding system. Optionally, the preset phase difference range is 90°-180°.
[0103] Among them, the zero-sequence CT of the feeder refers to the CT connected in series in the primary side line of the distribution network feeder, which is used to sense and convert the zero-sequence current signal of the feeder.
[0104] The polarity verification result refers to the judgment conclusion on whether the zero-sequence CT polarity of the feeder is correct, obtained by matching the phase difference with the preset phase difference range. Specifically, it includes two cases: no polarity reversal fault and polarity reversal fault.
[0105] Among them, the polarity reversal fault refers to the fault state in which the primary and secondary sides of the zero-sequence CT have opposite polarities, resulting in the zero-sequence current phase collected by the CT being opposite to the actual zero-sequence current phase of the feeder. This polarity reversal fault will cause the fault selection device to receive incorrect phase data, leading to misjudgment of the line selection.
[0106] In one possible implementation, if the phase difference is within a preset phase difference range, the polarity check result is determined to be that the zero-sequence CT does not have a polarity reversal fault. Conversely, if the phase difference is outside the preset range, the polarity check result is determined to be that the zero-sequence CT has a polarity reversal fault.
[0107] In the above implementation, the preset phase difference range is determined based on the standard phase difference range between the zero-sequence current of the faulty line and the zero-sequence voltage of the bus when the zero-sequence CT polarity is correct. The polarity verification result is quickly determined by judging whether the phase difference is within the preset phase difference range, thus ensuring the efficiency and accuracy of the verification.
[0108] The zero-sequence CT polarity verification method provided in this application involves obtaining the zero-sequence voltage of the distribution network bus and the zero-sequence current of the feeder within one cycle after a protection trip occurs on a distribution network feeder and the fault disappears after the trip. Then, the amplitudes of the zero-sequence voltage and zero-sequence current of the bus are calculated using a pre-set fitting function. Next, the phase difference between the zero-sequence voltage and zero-sequence current is determined based on these amplitudes. Finally, the polarity verification result of the zero-sequence CT of the feeder is determined based on the phase difference and a preset phase difference range. In this technical solution, after a protection trip occurs on a distribution network feeder and the fault disappears, the zero-sequence voltage of the bus and the zero-sequence current of the feeder within one cycle are obtained. The amplitudes of these two values are calculated using a fitting function, and the phase difference is determined. The polarity verification result is then obtained by combining this with a preset phase difference range. This solution does not rely on analog signals or externally injected signals. It directly uses electrical signals under actual working conditions after a fault to perform verification. This avoids the impact of power outage verification on power supply reliability and solves the problems of high cost and susceptibility to interference in live injection verification. It greatly improves the accuracy and adaptability of verification, ensures accurate zero-sequence CT polarity judgment results, provides core guarantee for the reliable operation of fault location devices, and meets the needs of efficient operation and maintenance of distribution networks.
[0109] Optionally, in some embodiments, if a reverse polarity fault is determined in the zero-sequence current transformer (CT) of the feeder, the phase of the acquired zero-sequence current will be opposite to the actual phase, directly causing misjudgment in subsequent fault location operations, delaying fault isolation time and expanding the power outage area. To compensate for this defect, the reverse polarity zero-sequence current can be corrected to ensure that subsequent fault location operations can be carried out based on real current data.
[0110] Specifically, if the polarity check result indicates that the zero-sequence CT has a polarity reverse fault, the zero-sequence current of the feeder will be reversed, and the value obtained from the operation will be determined as the target zero-sequence current. The target zero-sequence current will be used for subsequent fault selection operations.
[0111] The target zero-sequence current can be determined using the following formula:
[0112]
[0113] in, The target zero-sequence current.
[0114] The subsequent fault location operation refers to the operation in which the fault location device of the substation compares the phase characteristics of each line based on the target zero-sequence current and parameters such as the bus zero-sequence voltage to locate the faulty line in the distribution network.
[0115] Optionally, in the above embodiments, the signal deviation caused by reverse polarity connection of the zero-sequence CT is effectively compensated, so that the target zero-sequence current can truly reflect the actual zero-sequence state of the feeder, providing accurate data support for subsequent distribution network fault location. Through this correction operation, misjudgment of fault location caused by reverse polarity connection is avoided, ensuring that the faulty line can be quickly and accurately located and isolated, shortening fault handling time, reducing the power outage area, and significantly improving the reliability and efficiency of distribution network operation and maintenance.
[0116] Figure 3 Flowchart of the zero-sequence CT polarity verification method provided in this application Figure 2 ,like Figure 3 As shown, the method includes:
[0117] S301, the feeder tripped due to protection failure.
[0118] S302. Determine whether the fault has disappeared after the protection trips.
[0119] If yes, then execute S303; otherwise, check for other faults.
[0120] S303. Obtain the zero-sequence voltage of the bus and the zero-sequence current of the feeder in a distribution network within one cycle.
[0121] S304. Calculate the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current of the bus using a pre-defined fitting function.
[0122] S305. Determine the phase difference between the zero-sequence voltage and the zero-sequence current of the busbar based on the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current.
[0123] S306. Determine whether the phase difference is between 90° and 180°.
[0124] If yes, then execute S307; otherwise, execute S308.
[0125] S307. The polarity check result is zero. The CT does not have a polarity reversal fault.
[0126] S308. The polarity check result indicates that the zero-sequence CT has a reverse polarity connection fault.
[0127] S309. Invert the zero-sequence current of the feeder and determine the value obtained from the operation as the target zero-sequence current.
[0128] S310, Perform subsequent fault selection operations based on the target zero-sequence current.
[0129] Based on the zero-order CT polarity verification method provided in various embodiments, the zero-order CT polarity verification method has the following technical advantages:
[0130] 1. Verification is initiated only when the feeder protection trips and the fault disappears, ensuring that the verification object is the faulty line. The collected bus zero-sequence voltage and zero-sequence current data are all derived from real single-phase grounding fault conditions, ensuring the effectiveness and relevance of the verification data.
[0131] 2. Based on the phase characteristics of the zero-sequence voltage and zero-sequence current of the bus under real fault conditions, the phase difference between the two is calculated and compared with a preset range to directly identify the polarity reversal fault of the zero-sequence CT, avoiding the verification deviation caused by relying on analog signals.
[0132] 3. The verification process is automatically triggered when the protection trips or the fault disappears, eliminating the need for manual power outage operations or the configuration of external injection test equipment, which greatly improves verification efficiency and reduces operation and maintenance costs.
[0133] 4. If a polarity reversal fault is detected, dynamic phase compensation is achieved by reversing the zero-sequence current. The corrected target zero-sequence current is used as the input data of the fault selection device to ensure that the current data received by the fault selection device is accurate and reliable.
[0134] Figure 4 A schematic diagram of the zero-sequence CT polarity verification device provided in this application is shown below. Figure 4 As shown, the zero-sequence CT polarity verification device 40 provided in this embodiment includes:
[0135] The acquisition module 401 is used to acquire the zero-sequence voltage of the bus and the zero-sequence current of the feeder in a cycle if the protection trips the feeder of the distribution network and the fault of the feeder disappears after the protection trips.
[0136] The calculation module 402 is used to calculate the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current of the bus using a pre-set fitting function.
[0137] The first determining module 403 is used to determine the phase difference between the zero-sequence voltage and the zero-sequence current of the bus based on the amplitude of the zero-sequence voltage and the amplitude of the zero-sequence current of the bus.
[0138] The second determining module 404 is used to determine the polarity verification result of the zero-sequence CT of the feeder based on the phase difference and the preset phase difference range.
[0139] In one possible implementation, the second determining module 404 is specifically used for:
[0140] If the phase difference is within the preset phase difference range, the polarity check result is determined to be that the zero-sequence CT does not have a polarity reversal fault.
[0141] Conversely, if the polarity check result is negative, it indicates that the zero-sequence CT has a reverse polarity connection fault.
[0142] In one possible implementation, the preset phase difference range is 90°-180°.
[0143] In one possible implementation, the fitting function is an n×2 matrix, where n is the number of sampling points, each row represents the signal component at a sampling time, the first column represents the sine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network, and the second column represents the cosine function values corresponding to the first to the nth sampling points of the power frequency of the distribution network.
[0144] In one possible implementation, the computing module 402 is specifically used for:
[0145] Through formula Calculate the amplitude of the zero-sequence voltage at the bus.
[0146] Through formula Calculate the amplitude of the zero-sequence current.
[0147] in, The amplitude of the zero-sequence voltage of the busbar. This is the zero-sequence voltage of the bus. For the fitting function, The amplitude of the zero-sequence current. The amplitude of the zero-sequence current.
[0148] In one possible implementation, the first determining module 403 is specifically used for:
[0149] Through formula Determine the phase difference between the zero-sequence voltage and zero-sequence current of the bus.
[0150] in, This represents the phase difference.
[0151] In one possible implementation, the zero-sequence CT polarity verification device 40 further includes a third module for:
[0152] If the polarity check result indicates that the zero-sequence CT has a polarity reverse fault, the zero-sequence current of the feeder will be reversed, and the value obtained from the operation will be determined as the target zero-sequence current. The target zero-sequence current will be used for subsequent fault selection operations.
[0153] The zero-sequence CT polarity verification device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.
[0154] Figure 5 A schematic diagram of the structure of the electronic device provided in this application. Figure 5 As shown, the electronic device 50 provided in this embodiment includes at least one processor 501 and a memory 502. Optionally, the electronic device 50 further includes a communication component 503. The processor 501, memory 502, and communication component 503 are connected via a bus 504.
[0155] In a specific implementation, at least one processor 501 executes computer execution instructions stored in memory 502, causing at least one processor 501 to perform the above-described method.
[0156] The specific implementation process of processor 501 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.
[0157] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.
[0158] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.
[0159] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.
[0160] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.
[0161] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.
[0162] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random-Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.
[0163] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an application-specific integrated circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.
[0164] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.
[0165] 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 network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.
[0166] In addition, the functional units in the various embodiments of the present invention 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.
[0167] If a function 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 invention, or the part that contributes to the prior art, or a 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 of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.
[0168] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.
[0169] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.
Claims
1. A zero sequence CT polarity verification method, characterized in that, The method comprises the following steps: If a feeder of a power distribution network is tripped by protection and the fault of the feeder disappears after the tripping, bus zero sequence voltage of the power distribution network and zero sequence current of the feeder within a period are obtained; Amplitudes of the bus zero sequence voltage and the zero sequence current are calculated respectively by a preset fitting function; A phase difference between the bus zero sequence voltage and the zero sequence current is determined according to the amplitudes of the bus zero sequence voltage and the zero sequence current; A polarity check result of a zero sequence current transformer (CT) of the feeder is determined according to the phase difference and a preset phase difference range.
2. The method of claim 1, wherein, The determination of the polarity check result of the zero sequence CT of the feeder according to the phase difference and the preset phase difference range comprises: If the phase difference is within the preset phase difference range, it is determined that the polarity check result is that the zero sequence CT does not have a polarity connection failure; Otherwise, it is determined that the polarity check result is that the zero sequence CT has a polarity connection failure.
3. The method according to claim 1 or 2, characterized in that, The preset phase difference range is 90°-180°.
4. The method of claim 1, wherein, The fitting function is an n×2 matrix, where n is a number of sampling points, each row is a signal component at a sampling time, the first column is a sine function value corresponding to the first sampling point to the n-th sampling point of a power frequency of the power distribution network, and the second column is a cosine function value corresponding to the first sampling point to the n-th sampling point of the power frequency of the power distribution network.
5. The method according to claim 1 or 4, characterized in that, The calculation of the amplitudes of the bus zero sequence voltage and the zero sequence current by the preset fitting function comprises: The amplitude of the bus zero sequence voltage is calculated by the formula Vbus,0 = Vbus,1 - Vbus,2 The amplitude of the zero sequence current is calculated by the formula I0= Ia- Ib- Ic wherein, is the amplitude of the bus zero sequence voltage, is the bus zero sequence voltage, is the fitting function, is the amplitude of the zero sequence current, is the amplitude of the zero sequence current.
6. The method of claim 5, wherein, The determination of the phase difference between the bus zero sequence voltage and the zero sequence current according to the amplitudes of the bus zero sequence voltage and the zero sequence current comprises: Through formula Determine the phase difference between the zero-sequence voltage and the zero-sequence current of the bus; wherein is the phase difference.
7. The method of any one of claims 1, 2, 4, or 6, wherein, The method further comprises: If the polarity check result indicates that the zero sequence CT has a polarity connection failure, the zero sequence current of the feeder is subjected to an inversion operation, and a value obtained by the operation is determined as a target zero sequence current, which is used for subsequent fault line selection operation.
8. A zero sequence CT polarity verification device, characterized by, The method comprises the following steps: An obtaining module is configured to, if a feeder of a power distribution network is tripped by protection and the fault of the feeder disappears after the tripping, obtain bus zero sequence voltage of the power distribution network and zero sequence current of the feeder within a period; A calculating module is configured to calculate amplitudes of the bus zero sequence voltage and the zero sequence current respectively by a preset fitting function; A first determining module is configured to determine a phase difference between the bus zero sequence voltage and the zero sequence current according to the amplitudes of the bus zero sequence voltage and the zero sequence current; A second determining module is configured to determine a polarity check result of a zero sequence current transformer (CT) of the feeder according to the phase difference and a preset phase difference range.
9. An electronic device, comprising: The method comprises the following steps: A memory and a processor; The memory stores computer execution instructions; The processor executes the computer execution instructions stored in the memory, so that the processor executes the method in any one of claims 1-7.
10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer execution instructions, and the computer execution instructions are executed by the processor to implement the method in any one of claims 1-7.
11. A computer program product, characterised in that, A computer program comprising computer program elements which, when executed by a processor, perform the method of any of claims 1-7. A computer program comprising computer program elements which, when executed by a processor, perform the method of any of claims 1-7.