CT neutral line resistance abnormity judgment method and system under secondary intelligent operation and maintenance platform

Abstract

The invention relates to the technical field of power system operation and maintenance, and the method comprises the steps that a secondary intelligent operation and maintenance management and control platform obtains fault current and voltage data of protection devices on the two sides of a power transmission line, the secondary intelligent operation and maintenance management and control platform carries out a CT neutral line resistance overlarge intelligent judgment process, and the CT neutral line resistance overlarge intelligent judgment process is carried out according to the CT neutral line resistance overlarge criterion. And the secondary intelligent operation and maintenance management and control issues alarm information that the resistance of the neutral line is too large when the CT is broken. According to the method, data access and data processing advantages of a secondary intelligent operation and maintenance management and control platform are utilized, based on voltage and current characteristics when the CT neutral line resistance is too large, through a current amplitude criterion, a phase criterion and a waveform criterion, hidden dangers of too large CT neutral line resistance are found in time, and risks of operation refusal and maloperation are prevented.

Description

Technical Field

[0001] This invention relates to the field of power system operation and maintenance technology, and in particular to a method and system for judging abnormal neutral line resistance of CT under a secondary intelligent operation and maintenance platform. Background Technology

[0002] Relay protection is the first line of defense for the safe and stable operation of a power system, and a good neutral line in the current transformer (CT) is a prerequisite for the correct operation of relay protection devices. Common CT neutral line problems mainly include two categories: excessive neutral line resistance and neutral line breakage. Both of these can lead to maloperation or failure to operate the protection system. Therefore, it is very important to detect and eliminate CT neutral line problems in a timely manner.

[0003] Existing research focuses primarily on the problem of neutral line breakage in current transformers (CTs). Patent CN215641782U discloses a device for detecting neutral line breakage in current transformers, patent CN111948575A discloses a method and device for detecting neutral line breakage on the secondary side of current transformers, and patent CN114019417A discloses a method for detecting open circuit in the neutral line of a line protection current loop. Although neutral line breakage in CTs has serious consequences, its occurrence probability is low. However, the problem of excessive neutral line resistance in CTs caused by poor terminal contact and poor CT operating environment is more common. Yet, existing research rarely mentions how to detect excessive neutral line resistance in CTs.

[0004] The patent with publication number CN113238172A discloses a method for judging the abnormality of the neutral line of a current transformer based on the neutral line resistance. It judges whether the neutral line resistance of the current transformer is too large by comparing whether the neutral line resistance value is within the range of the first threshold resistance and the second threshold resistance. It reveals the necessity of detecting the excessive neutral line resistance of the current transformer, but does not describe how to determine the values ​​of the first threshold resistance and the second threshold resistance.

[0005] Therefore, in order to prevent protection failures and malfunctions, there is an urgent need for a method to quickly monitor whether the neutral line resistance of the CT is too high, so as to issue alarm information in a timely manner and quickly eliminate the defect. Summary of the Invention

[0006] In view of the aforementioned existing problems, the present invention is proposed.

[0007] Therefore, this invention provides a method for judging abnormal resistance of CT neutral line under a secondary intelligent operation and maintenance platform. It can promptly detect the hidden danger of excessive resistance of CT neutral line through current amplitude criteria, phase criteria, and waveform criteria, and prevent the risk of protection failure or false operation.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for judging abnormal neutral line resistance of CT under a secondary intelligent operation and maintenance platform, comprising: the secondary intelligent operation and maintenance management platform acquiring fault current and voltage data of protection devices on both sides of the transmission line; the secondary intelligent operation and maintenance management platform carrying out an intelligent judgment process for excessive neutral line resistance of CT; and issuing alarm information for CT neutral line resistance that meets the judgment criteria.

[0009] As a preferred embodiment of the abnormal CT neutral line resistance judgment method under the secondary intelligent operation and maintenance platform of the present invention, the intelligent operation and maintenance management platform includes an information platform for the dispatching agency to carry out remote related business for the secondary equipment at the plant end, which realizes the acquisition of current and voltage data of protection devices, realizes intelligent judgment of excessive CT neutral line resistance, and issues "CT neutral line resistance too high" alarm for those that do not meet the requirements after judgment.

[0010] The path for the secondary intelligent operation and maintenance management platform to obtain fault current and voltage data of the protection devices on both sides of the transmission line is as follows: the fault current and voltage of the protection devices on both sides of the transmission line are sent to the secondary intelligent operation and maintenance management platform through the protection information substation.

[0011] As a preferred embodiment of the abnormal CT neutral line resistance judgment method under the secondary intelligent operation and maintenance platform described in this invention, the intelligent judgment process includes two parts: fault phase identification and CT neutral line resistance excessive feature identification.

[0012] When an external fault occurs, the voltage of the faulted phase of the transmission line drops, and the current of the faulted phase is a through current. Based on this characteristic, the faulted phase can be identified as follows:

[0013] U<0.9U N

[0014]

[0015] Where U represents the secondary voltage of a certain phase collected by the transmission line protection device, U N Represents the rated voltage on the secondary side, Arg() represents a function of the phase difference between the two phase voltages, I M IN represents the secondary current of a certain phase collected by the protection device on the M side of the transmission line, and IN represents the secondary current of a certain phase collected by the protection device on the N side of the transmission line. When the voltage and current of a certain phase of the transmission line protection device simultaneously meet the above conditions, this phase is considered to be the fault phase.

[0016] As a preferred embodiment of the abnormal CT neutral line resistance judgment method under the secondary intelligent operation and maintenance platform described in this invention, the CT neutral line resistance over-excess feature identification includes: when an external fault occurs in the transmission line, if the CT neutral line resistance is too large, then on the M side of the transmission line, the non-faulty phase will have an abnormal current with a waveform biased to one side of the coordinate axis, and the current amplitude of the non-faulty phase is less than that of the faulty phase, and the maximum current amplitude of the faulty phase leads the maximum current amplitude of the non-faulty phase by an angle, while on the N side of the transmission line, there is no obvious fault current in the non-faulty phase;

[0017] A current amplitude criterion is proposed based on the characteristics of fault phase current amplitude and the characteristics of non-fault current amplitude:

[0018]

[0019]

[0020] in, The secondary current collected by the protection device on the M side of the non-faulty phase of the transmission line. The secondary current collected by the protection device on the N-side of the non-faulty phase of the transmission line; The secondary current collected by the protection device on the M side of the faulty phase of the transmission line. The secondary current collected by the protection device on the N side of the fault phase of the transmission line is max(), which is a function to take the maximum value. When the neutral line resistance of the CT is too large, the fault current and the non-fault phase current of the transmission line meet the above characteristics. However, if only the current amplitude criterion is used, misjudgment will occur when both the external fault and the internal high resistance fault occur at the same time. It needs to be used in conjunction with other criteria.

[0021] As a preferred embodiment of the method for judging abnormal CT neutral line resistance under the secondary intelligent operation and maintenance platform described in this invention, the other criteria include: based on the fact that the abnormal current waveform of the non-faulty phase deviates to one side of the coordinate axis, and the maximum amplitude of the faulty phase current precedes the maximum amplitude of the non-faulty phase by an angle, a current anomaly criterion is proposed. The current anomaly criterion includes a phase criterion and a waveform criterion, wherein the phase criterion is:

[0022]

[0023] in, This represents the maximum value of the fault phase current. This represents the maximum value of the non-faulty phase current.

[0024] As a preferred embodiment of the method for judging abnormal resistance of CT neutral line under the secondary intelligent operation and maintenance platform described in this invention, the waveform criteria include criteria 1 and criteria 2, wherein waveform criteria 1 is:

[0025]

[0026] Where d′i(t) represents the derivative of the non-fault phase current at a certain point in the first half-cycle, and d′i(t+T / 2) represents the derivative of the non-fault phase current at the corresponding point in the second half-cycle. Waveform criterion 1 is used to continuously compare half-cycles. If a quarter-cycle satisfies the above criterion, the non-fault phase current waveform is considered to have poor symmetry. Considering that waveform criterion 1 is easily affected by the sampling rate of the protection device, waveform criterion 2 is further proposed:

[0027]

[0028] Where i1 represents the sampling point of the protection device for the first half cycle of the non-faulty phase current. i1 represents the average value of the sampling points of the non-faulty phase current during the first half-cycle of the protection device, and i2 represents the sampling points of the non-faulty phase current during the second half-cycle of the protection device. The average value of the sampling points of the protection device for the second half cycle of the non-fault phase current is given. If either waveform criterion 1 or criterion 2 is satisfied, it is considered that the waveform symmetry of the non-fault phase current is poor, and the non-fault phase current is biased to one side of the coordinate axis. It is considered that the neutral line resistance of the CT is too large.

[0029] As a preferred embodiment of the abnormal CT neutral line resistance judgment method under the secondary intelligent operation and maintenance platform of the present invention, the alarm information is released as follows: for those that meet the CT neutral line resistance too high criterion, the secondary intelligent operation and maintenance management system will automatically release the "CT neutral line resistance too high" alarm information and send it to relevant personnel as soon as possible to ensure that the operation and maintenance personnel can know the fault information immediately and realize the rapid location and handling of the fault.

[0030] The alarm information includes detailed information such as the time, location, and outlier values ​​of the fault, allowing maintenance personnel to understand the fault situation more accurately and pinpoint the fault. Through the monitoring interface of the secondary intelligent maintenance platform, they can view real-time data and historical records to further analyze the cause of the fault and provide a basis for troubleshooting.

[0031] Another objective of this invention is to provide a CT neutral line resistance anomaly judgment system based on a secondary intelligent operation and maintenance platform, which can intelligently monitor and judge abnormal neutral line resistance in real time.

[0032] As a preferred embodiment of the CT neutral line resistance anomaly judgment system based on a secondary intelligent operation and maintenance platform described in this invention, it includes: a data acquisition module, a data processing module, a threshold setting module, an alarm release module, a fault diagnosis and processing module, and a user interface module;

[0033] The data acquisition module is responsible for acquiring the resistance value data of the CT neutral line in real time. The data is acquired through monitoring equipment and transmitted to the cloud platform for centralized management through Internet of Things technology.

[0034] The data processing module processes the collected resistance value data, performs real-time analysis and judgment on the data, and detects whether there are any abnormal resistance values.

[0035] The threshold setting module presets a threshold value for the neutral line resistance of the CT based on actual conditions and experience. When the resistance value exceeds this threshold, the system will automatically determine that the resistance value is abnormal.

[0036] When the system detects an abnormal resistance value, the alarm publishing module will automatically publish alarm information and notify the operation and maintenance personnel via SMS, email, and audio-visual means.

[0037] The fault diagnosis and handling module allows maintenance personnel to diagnose and handle faults, view real-time data and historical records through the platform's monitoring interface, analyze the causes of faults, and take corresponding measures to repair them.

[0038] The user interface module provides an operating interface for operation and maintenance personnel. Through this interface, operation and maintenance personnel can view real-time data and historical records, set thresholds, and handle alarm information.

[0039] A computer device includes a memory and a processor, wherein the memory stores a computer program, characterized in that the processor executes the computer program to implement the steps of a method for judging abnormal neutral line resistance of a CT under a secondary intelligent operation and maintenance platform.

[0040] A computer-readable storage medium storing a computer program thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of a method for judging abnormal resistance of the neutral line of a CT under a secondary intelligent operation and maintenance platform.

[0041] The beneficial effects of the present invention are as follows: The present invention provides an intelligent judgment method for excessive neutral line resistance of CT based on a secondary intelligent operation and maintenance management platform. Based on the voltage and current characteristics when the neutral line resistance of CT is too high, the method uses current amplitude criteria, phase criteria, and waveform criteria to promptly detect the hidden danger of excessive neutral line resistance of CT, prevent the risk of protection failure or false operation, accurately locate the fault location of CT, and realize rapid fault elimination. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0043] Figure 1 This is a schematic diagram of a method for judging abnormal resistance of CT neutral line under a secondary intelligent operation and maintenance platform provided in an embodiment of the present invention.

[0044] Figure 2 This is a schematic diagram of the protection current waveforms on both sides of the line in the method for judging abnormal resistance of the neutral line of a CT under a secondary intelligent operation and maintenance platform provided in an embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the workflow of a CT neutral line resistance anomaly judgment system based on a secondary intelligent operation and maintenance platform, provided as an embodiment of the present invention. Detailed Implementation

[0046] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0048] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0049] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0050] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0052] Example 1

[0053] Reference Figure 1 This is the first embodiment of the present invention, which provides a method for judging abnormal neutral line resistance of a CT under a secondary intelligent operation and maintenance platform, including:

[0054] S1: The secondary intelligent operation and maintenance management platform acquires fault current and voltage data of protection devices on both sides of the transmission line.

[0055] Furthermore, the intelligent operation and maintenance management platform includes an information platform for the dispatching agency to carry out remote related business for the secondary equipment at the plant and station end, which realizes the acquisition of current and voltage data of protection devices, realizes intelligent judgment of excessive neutral line resistance of CT, and issues "excessive neutral line resistance of CT" alarm for those that do not meet the requirements.

[0056] The path for the secondary intelligent operation and maintenance management platform to obtain fault current and voltage data of the protection devices on both sides of the transmission line is as follows: the fault current and voltage of the protection devices on both sides of the transmission line are sent to the secondary intelligent operation and maintenance management platform through the protection information substation.

[0057] S2: The secondary intelligent operation and maintenance management platform implements an intelligent judgment process for excessive neutral line resistance in CT.

[0058] Furthermore, the intelligent judgment process includes two parts: fault phase identification and CT neutral line resistance too high feature identification, which are carried out by the secondary intelligent operation and maintenance management platform.

[0059] When an external fault occurs, the voltage of the faulted phase of the transmission line drops, and the current of the faulted phase is a through current. Based on this characteristic, the faulted phase can be identified as follows:

[0060] U<0.9U N

[0061]

[0062] Where U represents the secondary voltage of a certain phase collected by the transmission line protection device, U N This represents the rated voltage of the secondary side, taken as... Arg() represents a function that takes the phase difference between two phase voltages, I MIN represents the secondary current of a certain phase collected by the protection device on the M side of the transmission line, and IN represents the secondary current of a certain phase collected by the protection device on the N side of the transmission line. When the voltage and current of a certain phase of the transmission line protection device simultaneously meet the above conditions, this phase is considered to be the fault phase.

[0063] It should be noted that the identification of excessive neutral line resistance in the CT includes the following: when an external fault occurs in the transmission line, if the neutral line resistance of the CT is too high, then on the M side of the transmission line, the non-faulty phase will have an abnormal current with a waveform biased to one side of the coordinate axis, and the current amplitude of the non-faulty phase will be less than that of the faulty phase. The maximum current amplitude of the faulty phase will lead the maximum current amplitude of the non-faulty phase by an angle. On the N side of the transmission line, there is no obvious fault current in the non-faulty phase.

[0064] A current amplitude criterion is proposed based on the characteristics of fault phase current amplitude and the characteristics of non-fault current amplitude:

[0065]

[0066]

[0067] in, The secondary current collected by the protection device on the M side of the non-faulty phase of the transmission line. The secondary current collected by the protection device on the N-side of the non-faulty phase of the transmission line; The secondary current collected by the protection device on the M side of the faulty phase of the transmission line. The secondary current collected by the protection device on the N side of the fault phase of the transmission line is max(), which is a function to take the maximum value. When the neutral line resistance of the CT is too large, the fault current and the non-fault phase current of the transmission line meet the above characteristics. However, if only the current amplitude criterion is used, misjudgment will occur when both the external fault and the internal high resistance fault occur at the same time. It needs to be used in conjunction with other criteria.

[0068] Furthermore, the other criteria include, based on the fact that the abnormal current waveform of the non-faulty phase deviates to one side of the coordinate axis, and the moment when the current amplitude of the faulty phase leads the moment when the current amplitude of the non-faulty phase reaches its maximum by an angle, a current anomaly criterion is proposed. The current anomaly criterion includes a phase criterion and a waveform criterion, wherein the phase criterion is:

[0069]

[0070] in, This represents the maximum value of the fault phase current. This represents the maximum value of the non-faulty phase current.

[0071] Furthermore, the waveform criterion includes criterion 1 and criterion 2, wherein waveform criterion 1 is:

[0072]

[0073] Where d′i(t) represents the derivative of the non-fault phase current at a certain point in the first half-cycle, and d′i(t+T / 2) represents the derivative of the non-fault phase current at the corresponding point in the second half-cycle. Waveform criterion 1 is used to continuously compare half-cycles. If a quarter-cycle satisfies the above criterion, the non-fault phase current waveform is considered to have poor symmetry. Considering that waveform criterion 1 is easily affected by the sampling rate of the protection device, waveform criterion 2 is further proposed:

[0074]

[0075] Where i1 represents the sampling point of the protection device for the first half cycle of the non-faulty phase current. i1 represents the average value of the sampling points of the non-faulty phase current during the first half-cycle of the protection device, and i2 represents the sampling points of the non-faulty phase current during the second half-cycle of the protection device. The average value of the sampling points of the protection device for the second half cycle of the non-fault phase current is given. If either waveform criterion 1 or criterion 2 is satisfied, it is considered that the waveform symmetry of the non-fault phase current is poor, and the non-fault phase current is biased to one side of the coordinate axis. It is considered that the neutral line resistance of the CT is too large.

[0076] S3: For cases that meet the CT neutral line resistance too high criterion, secondary intelligent operation and maintenance management will issue alarm information.

[0077] Furthermore, the alarm information release includes the following: for cases that meet the CT neutral line resistance too high criterion, the secondary intelligent operation and maintenance management system will automatically release an "CT neutral line resistance too high" alarm information and send it to relevant personnel as soon as possible to ensure that operation and maintenance personnel can immediately know the fault information and realize the rapid location and handling of the fault.

[0078] The alarm information includes detailed information such as the time, location, and outlier values ​​of the fault, allowing maintenance personnel to understand the fault situation more accurately and pinpoint the fault. Through the monitoring interface of the secondary intelligent maintenance platform, they can view real-time data and historical records to further analyze the cause of the fault and provide a basis for troubleshooting.

[0079] Example 2

[0080] Reference Figure 2 As an embodiment of the present invention, a method for judging abnormal resistance of CT neutral line under a secondary intelligent operation and maintenance platform is provided. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0081] (1) Taking a 220kV line experiencing an A-phase fault outside the designated area as an example, the faulty phase has been identified as phase A. The protection current waveforms on both sides of the line during the fault are as follows: Figure 1 As shown, i 1A i 1B i 2A i 2BThese represent the phase A current on the M side, the phase B current on the M side, the phase A current on the N side, and the phase B current on the N side, respectively.

[0082] (2) First, the current amplitude criterion was used, and the judgment results are shown in Table 1. As can be seen from Table 1, the protection on the M side of the line has the problem of excessive CT neutral line resistance. However, in order to prevent misjudgment when both external and internal high resistance faults occur at the same time, phase and waveform criteria were further used to confirm whether the CT neutral line resistance was indeed excessive.

[0083] Table 1 Results of Current Amplitude Criteria

[0084]

[0085] Depend on Figure 2 It can be seen that, If the phase criterion and waveform criterion 2 are met, it is confirmed that the neutral line resistance of the CT on the M side of the line is too high, and the fault point is accurately located.

[0086] (4) Comparing the existing methods for troubleshooting excessive CT neutral line resistance with the method proposed in this invention, it can be seen that the method proposed in this invention is more efficient, realizing machine-assisted troubleshooting of excessive CT neutral line resistance, accurately locating the fault point before personnel set off, and achieving precise defect elimination.

[0087] Table 2 Comparison Results

[0088]

[0089]

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0091] Example 3

[0092] The third embodiment of the present invention differs from the first two embodiments in that:

[0093] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present 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 described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0094] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0095] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0096] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0097] Example 4

[0098] Reference Figure 3 As an embodiment of the present invention, a CT neutral line resistance anomaly judgment system based on a secondary intelligent operation and maintenance platform is provided, characterized in that: it includes a data acquisition module, a data processing module, a threshold setting module, an alarm release module, a fault investigation and processing module, and a user interface module.

[0099] The data acquisition module is responsible for collecting the resistance value data of the CT neutral line in real time. The data is acquired through monitoring equipment and transmitted to the cloud platform for centralized management via Internet of Things technology.

[0100] The data processing module processes the collected resistance value data, performs real-time analysis and judgment on the data, and detects whether there are any abnormal resistance values.

[0101] The threshold setting module presets a threshold value for the neutral line resistance of the CT based on actual conditions and experience. When the resistance value exceeds this threshold, the system will automatically determine that the resistance value is abnormal.

[0102] The alarm publishing module automatically publishes alarm information when the system detects abnormal resistance, notifying maintenance personnel via SMS, email, and audio-visual means.

[0103] The troubleshooting and handling module allows maintenance personnel to troubleshoot and handle faults. They can view real-time data and historical records through the platform's monitoring interface, analyze the causes of faults, and take corresponding measures to repair them.

[0104] The user interface module provides an operating interface for operations and maintenance personnel. Through this interface, they can view real-time data and historical records, set thresholds, and handle alarm information.

[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for judging abnormal neutral line resistance of CT under a secondary intelligent operation and maintenance platform, characterized in that: include, The secondary intelligent operation and maintenance management platform acquires fault current and voltage data of protection devices on both sides of the transmission line; The secondary intelligent operation and maintenance management platform implements an intelligent judgment process for excessive neutral line resistance in CTs. For cases that meet the criterion of excessive neutral line resistance in the CT, the secondary intelligent operation and maintenance management will issue an alarm message.

2. The method for judging abnormal resistance of CT neutral line under the secondary intelligent operation and maintenance platform as described in claim 1, characterized in that: The intelligent operation and maintenance management platform includes an information platform for the dispatching agency to carry out remote related business for the secondary equipment at the plant and station end, which realizes the acquisition of current and voltage data of protection devices, realizes intelligent judgment of excessive neutral line resistance of CT, and issues "excessive neutral line resistance of CT" alarm for those that do not meet the requirements. The path for the secondary intelligent operation and maintenance management platform to obtain fault current and voltage data of the protection devices on both sides of the transmission line is as follows: the fault current and voltage of the protection devices on both sides of the transmission line are sent to the secondary intelligent operation and maintenance management platform through the protection information substation.

3. The method for judging abnormal resistance of CT neutral line under the secondary intelligent operation and maintenance platform as described in claim 2, characterized in that: The intelligent judgment process includes two parts: fault phase identification and CT neutral line resistance too high feature identification, which are carried out by the secondary intelligent operation and maintenance management platform. When an external fault occurs, the voltage of the faulted phase of the transmission line drops, and the current of the faulted phase is a through current. Based on this characteristic, the faulted phase can be identified as follows: U<0.9U N Where U represents the secondary voltage of a certain phase collected by the transmission line protection device, U N Indicates the rated voltage of the secondary side, Arg() represents a function of the phase difference between the two phase voltages, I M IN represents the secondary current of a certain phase collected by the protection device on the M side of the transmission line, and IN represents the secondary current of a certain phase collected by the protection device on the N side of the transmission line. When the voltage and current of a certain phase of the transmission line protection device simultaneously meet the above conditions, this phase is considered to be the fault phase.

4. The method for judging abnormal resistance of CT neutral line under the secondary intelligent operation and maintenance platform as described in claim 3, characterized in that: The identification of excessive neutral line resistance in the CT includes power transmission. When a fault occurs outside the transmission line, if the neutral line resistance of the CT is too large, then on the M side of the transmission line, the non-faulty phase will have an abnormal current with a waveform biased to one side of the coordinate axis, and the current amplitude of the non-faulty phase will be less than that of the faulty phase. The maximum current amplitude of the faulty phase will lead the maximum current amplitude of the non-faulty phase by an angle. On the N side of the transmission line, there is no obvious fault current in the non-faulty phase. A current amplitude criterion is proposed based on the characteristics of fault phase current amplitude and the characteristics of non-fault current amplitude: in, The secondary current collected by the protection device on the M side of the non-faulty phase of the transmission line. The secondary current collected by the protection device on the N-side of the non-faulty phase of the transmission line; The secondary current collected by the protection device on the M side of the faulty phase of the transmission line. The secondary current collected by the protection device on the N side of the fault phase of the transmission line is max(), which is a function to take the maximum value. When the neutral line resistance of the CT is too large, the fault current and the non-fault phase current of the transmission line meet the above characteristics. However, if only the current amplitude criterion is used, misjudgment will occur when both the external fault and the internal high resistance fault occur at the same time. It needs to be used in conjunction with other criteria.

5. The method for judging abnormal resistance of CT neutral line under the secondary intelligent operation and maintenance platform as described in claim 4, characterized in that: The other criteria include, based on the fact that the abnormal current waveform of the non-faulty phase deviates to one side of the coordinate axis, and the maximum amplitude of the faulty phase current precedes the maximum amplitude of the non-faulty phase current by an angle, a current anomaly criterion is proposed. The current anomaly criterion includes a phase criterion and a waveform criterion, wherein the phase criterion is as follows: in, This represents the maximum value of the fault phase current. This represents the maximum value of the non-faulty phase current.

6. The method for judging abnormal resistance of CT neutral line under the secondary intelligent operation and maintenance platform as described in claim 5, characterized in that: The waveform criteria include criteria 1 and criteria 2, wherein waveform criteria 1 is: Where d′i(t) represents the derivative of the non-fault phase current at a certain point in the first half-cycle, and d′i(t+T / 2) represents the derivative of the non-fault phase current at the corresponding point in the second half-cycle. Waveform criterion 1 is used to continuously compare half-cycles. If a quarter-cycle satisfies the above criterion, the non-fault phase current waveform is considered to have poor symmetry. Considering that waveform criterion 1 is easily affected by the sampling rate of the protection device, waveform criterion 2 is further proposed: Where i1 represents the sampling point of the protection device for the first half cycle of the non-faulty phase current. i1 represents the average value of the sampling points of the non-faulty phase current during the first half-cycle of the protection device, and i2 represents the sampling points of the non-faulty phase current during the second half-cycle of the protection device. The average value of the sampling points of the protection device for the second half cycle of the non-fault phase current is given. If either waveform criterion 1 or criterion 2 is satisfied, it is considered that the waveform symmetry of the non-fault phase current is poor, and the non-fault phase current is biased to one side of the coordinate axis. It is considered that the neutral line resistance of the CT is too large.

7. The method for judging abnormal resistance of CT neutral line under the secondary intelligent operation and maintenance platform as described in claim 6, characterized in that: The alarm information includes the following: if the CT neutral line resistance is too high, the secondary intelligent operation and maintenance management system will automatically issue an alarm information "CT neutral line resistance too high" and send it to relevant personnel as soon as possible to ensure that operation and maintenance personnel can know the fault information immediately and realize the rapid location and handling of the fault. The alarm information includes detailed information such as the time, location, and outlier values ​​of the fault, allowing maintenance personnel to understand the fault situation more accurately and pinpoint the fault. Through the monitoring interface of the secondary intelligent maintenance platform, they can view real-time data and historical records to further analyze the cause of the fault and provide a basis for troubleshooting.

8. A CT neutral line resistance anomaly judgment system based on a secondary intelligent operation and maintenance platform as described in any one of claims 1 to 7, characterized in that: It includes a data acquisition module, a data processing module, a threshold setting module, an alarm release module, a fault diagnosis and handling module, and a user interface module; The data acquisition module is responsible for acquiring the resistance value data of the CT neutral line in real time. The data is acquired through monitoring equipment and transmitted to the cloud platform for centralized management through Internet of Things technology. The data processing module processes the collected resistance value data, performs real-time analysis and judgment on the data, and detects whether there are any abnormal resistance values. The threshold setting module presets a threshold value for the neutral line resistance of the CT based on actual conditions and experience. When the resistance value exceeds this threshold, the system will automatically determine that the resistance value is abnormal. When the system detects an abnormal resistance value, the alarm publishing module will automatically publish alarm information and notify the operation and maintenance personnel via SMS, email, and audio-visual means. The fault diagnosis and handling module allows maintenance personnel to diagnose and handle faults, view real-time data and historical records through the platform's monitoring interface, analyze the causes of faults, and take corresponding measures to repair them. The user interface module provides an operating interface for operation and maintenance personnel. Through this interface, operation and maintenance personnel can view real-time data and historical records, set thresholds, and handle alarm information.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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