Signal injection power system CT secondary circuit open circuit detection method and system

Abstract

The invention relates to the technical field of power system fault detection, in particular to a signal injection power system CT secondary circuit open circuit detection method and system, and the method comprises the steps: injecting a high-frequency constant-current source signal with a specific frequency at a monitoring point of a current transformer secondary circuit; detecting loop input impedance corresponding to the high-frequency constant-current source signal at the monitoring point; adjusting a reference preset alarm threshold value according to the environment temperature change and the equipment aging degree to obtain an adjusted alarm threshold value; when the module value of the loop input impedance is larger than the adjusted alarm threshold value, it is judged that an open-circuit fault occurs in the secondary loop of the current transformer; after the open-circuit fault is judged, starting a frequency sweeping mode, then detecting whether impedance sag occurs or not, and determining a corresponding characteristic frequency; and determining a section where the open-circuit fault point is located according to the detected characteristic frequency. The accuracy of open circuit detection of the current secondary circuit of the hydropower station is improved.

Description

Technical Field

[0001] This invention relates to the field of power system fault detection technology, and in particular to a method and system for detecting open circuits in the secondary circuit of a power system CT by signal injection. Background Technology

[0002] In hydropower station power systems, the reliability of the secondary circuit of current transformers (CTs) directly affects the safe and stable operation of the power station and the power grid. An open circuit in the CT secondary circuit is an extremely dangerous fault, generating high voltage at the open circuit point that endangers equipment and personnel safety, and causing relay protection devices to fail to operate or malfunction, potentially leading to serious consequences. Currently, detection methods for this type of fault have significant shortcomings: First, reliance on manual inspections and periodic calibrations is inefficient, lacks real-time performance, and poses high risks to personnel operating near high-voltage equipment; second, relying on the "CT disconnection" alarm of the protection device is a reactive alarm, unable to prevent the generation of high voltage, and has detection blind spots when the unit is lightly loaded or unloaded; third, traditional methods such as open delta voltage monitoring are all passive responses, only acting after dangerous high voltage occurs, unable to provide early warning, and lacking fault location capabilities. Hydropower station CT secondary circuits are typically longer and have more complex wiring; therefore, there is an urgent need for an active monitoring method and system that can provide early warning before open-circuit high voltage occurs and can accurately locate the fault point online. Summary of the Invention

[0003] This invention provides a method and system for detecting open circuits in the secondary circuit of current transformers (CTs) in power systems using signal injection. This method addresses the problems of passive lag, inability to provide early warning and location, high reliance on manual intervention, and the existence of detection blind spots in existing methods for detecting open circuits in the secondary circuit of current transformers.

[0004] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention is to provide a method for detecting open circuits in the secondary circuit of a power system CT by signal injection, comprising: Passive resonant tags are pre-set at multiple key nodes along the secondary circuit of the current transformer, each of which has a unique resonant frequency; several monitoring points are set in the secondary circuit of the current transformer, and a high-frequency constant current source signal of a specific frequency is injected into the monitoring points of the secondary circuit of the current transformer. The frequency of the high-frequency constant current source signal is higher than the power frequency, and the amplitude is in the milliampere range. At the monitoring point, the circuit input impedance corresponding to the high-frequency constant current source signal is detected; the baseline preset alarm threshold is adjusted by changes in ambient temperature and the degree of equipment aging to obtain the adjusted alarm threshold; when the magnitude of the circuit input impedance is greater than the adjusted alarm threshold, it is determined that an open circuit fault has occurred in the secondary circuit of the current transformer. After determining an open circuit fault, a frequency sweep mode is initiated, injecting a continuously varying scanning signal into the circuit. During the frequency sweep, the impedance dip is detected, and when an impedance dip occurs, the corresponding characteristic frequency is determined. The characteristic frequency is the resonant frequency of the passive resonant tag. Based on the detected characteristic frequency, the preset mapping relationship between "passive resonant tag and fault section" is queried to determine the section where the open circuit fault point is located.

[0005] Furthermore, the adjustment of the baseline preset alarm threshold based on changes in ambient temperature and the degree of equipment aging to obtain the adjusted alarm threshold includes: The first adjustment factor for obtaining the alarm threshold is based on the ambient temperature; A second adjustment factor for the alarm threshold is obtained based on the degree of equipment aging trend. The baseline preset alarm threshold is adjusted based on the first adjustment factor and the second adjustment factor of the alarm threshold to obtain the adjusted alarm threshold.

[0006] Furthermore, the first adjustment factor for obtaining the alarm threshold based on the ambient temperature is specifically expressed by the formula:

[0007] In the formula, This represents the average ambient temperature across all times within the reference window at each given moment. Indicates the reference ambient temperature. The first adjustment factor represents the alarm threshold. Represents a linear normalization function; The baseline ambient temperature is a preset value, and the reference window for each moment is a window with a length of five moments before and after it.

[0008] Furthermore, the second adjustment factor for obtaining the alarm threshold based on the degree of equipment aging trend is specifically expressed by the following formula:

[0009] In the formula, The second adjustment factor represents the alarm threshold. This represents the current long-term impedance trend value predicted by the trend analysis algorithm. Indicates the drift tracking coefficient. This represents the reference impedance at the initial commissioning of the system; Indicates the safety boundary value. This is an activation function used for data normalization. The drift tracking coefficient and safety boundary value are preset values.

[0010] Furthermore, the baseline preset alarm threshold is adjusted according to the first adjustment factor and the second adjustment factor of the alarm threshold to obtain the adjusted alarm threshold, which is specifically expressed by the formula:

[0011] In the formula, The first adjustment factor represents the alarm threshold. The second adjustment factor represents the alarm threshold. Indicates the baseline preset alarm threshold. This indicates the adjusted alarm threshold.

[0012] Furthermore, the section where the open-circuit fault point is located specifically refers to: If the resonant frequency of the Nth passive resonant tag is detected, but the resonant frequencies of the (N+1)th and subsequent passive resonant tags are not detected, then the open circuit point is determined to be between the Nth and (N+1)th passive resonant tags.

[0013] Furthermore, the frequency range of the high-frequency constant current source signal is from 1 kHz to 100 kHz.

[0014] A second aspect of the present invention is to provide a power system CT secondary circuit open circuit detection system with signal injection, comprising: Signal injection module: used to pre-set passive resonant tags at multiple key nodes along the secondary circuit of the current transformer, each passive resonant tag having a unique corresponding resonant frequency; set several monitoring points in the secondary circuit of the current transformer, and inject a high-frequency constant current source signal of a specific frequency at the monitoring points of the secondary circuit of the current transformer, the frequency of the high-frequency constant current source signal being higher than the power frequency and the amplitude being in the milliampere range; Adaptive threshold adjustment module: used to detect the loop input impedance corresponding to the high-frequency constant current source signal at the monitoring point; adjust the benchmark preset alarm threshold according to changes in ambient temperature and equipment aging to obtain the adjusted alarm threshold; when the magnitude of the loop input impedance is greater than the adjusted alarm threshold, it is determined that an open circuit fault has occurred in the secondary circuit of the current transformer. Fault Feature Scanning and Identification Module: After determining an open circuit fault, it initiates a frequency sweep mode and injects a continuously changing scanning signal into the circuit; during the frequency sweep, it detects whether an impedance dip occurs, and when an impedance dip occurs, it determines the corresponding characteristic frequency; wherein, the characteristic frequency is the resonant frequency of the passive resonant tag. Fault Section Precise Location Module: Based on the detected characteristic frequency, this module queries the preset "passive resonant tag-fault section" mapping relationship to determine the section where the open circuit fault point is located.

[0015] A third aspect of the present invention is to provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the aforementioned method for detecting open circuits in the secondary circuit of a power system CT with signal injection.

[0016] A fourth aspect of the present invention is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned method for detecting open circuits in the secondary circuit of a power system CT with signal injection.

[0017] Compared with the prior art, the beneficial effects of this invention are as follows: Several monitoring points are set in the secondary circuit of the current transformer; a high-frequency constant current source signal of a specific frequency is injected into these monitoring points; early, proactive, and safe monitoring of open circuits in the CT secondary circuit is achieved, laying the foundation for fault early warning; at the monitoring points, the circuit input impedance corresponding to the high-frequency constant current source signal is detected; the preset alarm threshold is adjusted based on changes in ambient temperature and equipment aging to obtain an adjusted alarm threshold; when the magnitude of the circuit input impedance is greater than the adjusted alarm threshold, an open circuit fault is determined in the secondary circuit of the current transformer; through adaptive threshold adjustment, false alarms caused by environmental changes and equipment aging are significantly reduced, improving monitoring reliability; after determining an open circuit fault, a frequency sweep mode is activated. A continuously varying frequency scanning signal is injected into the circuit. During the frequency sweep, impedance dips are detected, and the corresponding characteristic frequency is determined when an impedance dip occurs. The characteristic frequency is the resonant frequency of the passive resonant tag. By scanning and exciting the passive resonant tag, the physical open circuit point is transformed into an identifiable characteristic frequency, providing a key basis for precise location. Based on the detected characteristic frequency, a preset mapping relationship between the passive resonant tag and the fault section is queried to determine the section where the open circuit fault point is located. By using the characteristic frequency and the preset mapping relationship, precise section-level location of the open circuit fault point is achieved, greatly improving maintenance efficiency. This solves the problems of passive lag, inability to provide early warning and location, high reliance on manual intervention, and the existence of detection blind spots in existing open circuit detection methods for current transformer secondary circuits. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0019] Figure 1This invention provides a schematic flowchart of the steps for a power system CT secondary circuit open circuit detection method with signal injection; Figure 2 This invention provides a schematic flowchart of a power system CT secondary circuit open circuit detection system with signal injection. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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 scope of protection of the present invention.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] To address the problems existing in the background technology, a method and system for detecting open circuits in the secondary circuit of a CT in a power system by signal injection has been developed, which has significant practical implications.

[0023] like Figure 1 As shown, the first aspect of the present invention is to provide a method for detecting open circuits in the secondary circuit of a power system CT by signal injection, comprising the following steps: Step S1: At multiple key nodes along the secondary circuit of the current transformer, passive resonant tags are pre-set, each passive resonant tag having a unique corresponding resonant frequency; several monitoring points are set in the secondary circuit of the current transformer, and a high-frequency constant current source signal of a specific frequency is injected into the monitoring points of the secondary circuit of the current transformer. The frequency of the high-frequency constant current source signal is higher than the power frequency, and the amplitude is in the milliampere range.

[0024] The frequency range of the high-frequency constant current source signal is 1kHz to 100kHz (kilohertz).

[0025] It should be noted that the core purpose of this step is to construct an active monitoring network with precise positioning capabilities. By pre-setting passive tags with different resonant frequencies at key nodes, it is equivalent to setting a unique "identity card" for each section of the circuit; at the same time, a safe high-frequency signal is injected into the monitoring points. When the circuit is normal, the system provides early warning by monitoring the signal impedance; once an open circuit occurs, it can accurately locate the faulty section by scanning and identifying the location of the tags that can be excited, thus realizing the leap from "whether there is a fault" to "where the fault is," greatly improving the accuracy of detection and maintenance efficiency.

[0026] Step S2: At the monitoring point, detect the circuit input impedance corresponding to the high-frequency constant current source signal; adjust the preset alarm threshold according to changes in ambient temperature and equipment aging to obtain the adjusted alarm threshold; when the magnitude of the circuit input impedance is greater than the adjusted alarm threshold, determine that an open circuit fault has occurred in the secondary circuit of the current transformer.

[0027] It should be noted that due to the influence of changes in ambient temperature, equipment aging, etc., the preset fixed threshold may cause false alarms when there are slight changes in ambient temperature or equipment aging. Therefore, an alarm threshold that can be dynamically adjusted according to ambient temperature and equipment aging is needed to improve the accuracy of fault detection.

[0028] It's important to further explain that when the ambient temperature rises, the resistance of the copper conductors in the cable constituting the secondary circuit increases. These factors lead to an increase in the resistive component of the entire circuit under high-frequency signals, resulting in a slight, reversible increase in the magnitude of the input impedance seen from the injection point as the temperature rises. Conversely, the impedance decreases accordingly when the temperature decreases. Through long-term monitoring, the system learns this positive correlation between impedance and temperature. Therefore, when the temperature sensor detects a significant increase in ambient temperature, the system will correspondingly raise the alarm threshold, allowing the impedance to fluctuate within the normal range, thus avoiding false alarms during hot afternoons. Similarly, in low-temperature environments, the system will lower the threshold to ensure sufficient monitoring sensitivity for minor open-circuit faults even after the impedance baseline decreases.

[0029] Specifically, a first adjustment factor for the alarm threshold is obtained based on the ambient temperature; wherein, the first adjustment factor for the alarm threshold is expressed by the formula:

[0030] In the formula, This represents the average ambient temperature across all times within the reference window at each given moment. Indicates the reference ambient temperature. The first adjustment factor represents the alarm threshold. This represents the linear normalization function.

[0031] In this embodiment, the reference ambient temperature is 20 degrees Celsius. However, this embodiment does not impose a specific limit on the reference ambient temperature; the implementer can determine it according to specific circumstances. Each reference window is a window with a length of five time points before and after it.

[0032] It's important to further clarify that equipment aging is a slow, irreversible degradation process. Aging directly causes a slow but continuous upward drift in the high-frequency impedance of the circuit over time. For this slow change, the system needs to distinguish between normal "aging" and sudden "failures." Through trend analysis algorithms (such as moving averages or linear regression), the system can capture this slowly rising baseline. The threshold is also adjusted slowly and progressively upwards to track this baseline drift caused by aging, preventing false alarms caused by cumulative changes over time. However, a safety boundary is needed. If the rate of impedance increase exceeds the preset aging rate limit, the system should trigger a "health degradation" warning, rather than simply adjusting the threshold, as this might indicate a potential failure risk.

[0033] Specifically, a second adjustment factor for the alarm threshold is obtained based on the degree of equipment aging; wherein the second adjustment factor for the alarm threshold is expressed by the formula:

[0034] In the formula, The second adjustment factor represents the alarm threshold. This represents the current impedance long-term trend value predicted by trend analysis algorithms (such as linear regression). This represents the drift tracking coefficient (set to 0.5 in this embodiment, where the drift tracking coefficient is not specifically limited in this embodiment). This represents the reference impedance at the initial commissioning of the system (a value set manually based on experience). This represents the safety margin value (a fixed safety margin factor, such as γ=0.2 or 20%; it ensures that the threshold is always a fixed percentage higher than the normal baseline, as a buffer zone to capture sudden or nonlinear changes not covered by the trend term). This is the activation function used for data normalization.

[0035] Specifically, the baseline preset alarm threshold is adjusted according to the first adjustment factor and the second adjustment factor of the alarm threshold to obtain the adjusted alarm threshold; wherein, the adjusted alarm threshold is specifically expressed as follows:

[0036] In the formula, The first adjustment factor represents the alarm threshold. The second adjustment factor represents the alarm threshold. Indicates the baseline preset alarm threshold. This indicates the adjusted alarm threshold.

[0037] Thus, the adjusted alarm thresholds are obtained using the methods described above.

[0038] Step S3: After determining an open circuit fault, start the frequency sweep mode and inject a continuously changing scanning signal into the circuit; during the frequency sweep, detect whether an impedance dip occurs, and when an impedance dip occurs, determine the corresponding characteristic frequency; wherein, the characteristic frequency is the resonant frequency of the passive resonant tag.

[0039] During the frequency sweep process, signal processing and peak detection algorithms are used to detect impedance dips. The signal processing and peak detection algorithms are well-known technologies and will not be described in detail here. The characteristic frequency is the resonant frequency of the passive resonant tag.

[0040] It should be noted that the core purpose of this step is to initiate a precise location procedure after an open circuit is detected. By scanning and exciting passive resonant tags pre-installed along the circuit, the physical fault point is converted into an identifiable frequency signal. Specifically, by analyzing the characteristic frequencies of impedance dips, the system can uniquely determine the location of the tag closest to the injection point and not blocked by the open circuit. This precisely narrows the fault range to a specific segment "between this tag and the next unexcited tag," achieving a crucial leap from "detecting an anomaly" to "locating the fault," greatly improving maintenance efficiency and accuracy.

[0041] Step S4: Based on the detected characteristic frequency, query the preset "passive resonant tag-fault section" mapping relationship to determine the section where the open circuit fault point is located.

[0042] Specifically, if the resonant frequency of the Nth passive resonant tag is detected, but the resonant frequencies of the (N+1)th and subsequent passive resonant tags are not detected, then the open circuit point is determined to be located between the Nth and (N+1)th passive resonant tags.

[0043] It should be noted that the core purpose of this step is to convert the identified electrical characteristics (frequency) into specific physical location information. Its function is that the system, by querying a pre-defined "frequency-location" mapping table, associates the detected characteristic frequency with the corresponding unique passive resonant tag, thereby accurately determining the specific loop segment between that tag and the next undetected tag where the open-circuit fault point is located. Ultimately, this transforms the abstract fault signal into precise location information that can directly guide maintenance actions, greatly improving troubleshooting efficiency and safety.

[0044] The specific implementation process is illustrated using the A-phase secondary circuit of a generator outlet CT in a hydropower station as an example.

[0045] The signal injection / detection module of this invention is installed at the terminal block of the generator protection cabinet. Passive resonant tags with resonant frequencies of 55kHz, 65kHz, and 75kHz are installed in series at three key nodes: the CT main body junction box outlet, the main transformer site terminal box, and the protection cabinet entrance. During normal system operation, the module injects a constant current signal of 1mA at a frequency of 60kHz, monitoring an impedance of approximately a few ohms (mainly cable resistance and load impedance). On one occasion, vibration caused a screw inside the main transformer site terminal box to loosen, creating an open circuit. The module detected a sudden increase in impedance to several thousand ohms at 60kHz, immediately triggering an "open circuit warning." The system automatically initiated a frequency sweep program, finding a sharp impedance dip at 55kHz (the 55kHz tag was activated), but no response at 65kHz and 75kHz. Therefore, the system accurately determined that "the open circuit point is located at the cable or connection point between the CT main body junction box (55kHz tag) and the main transformer site terminal box (65kHz tag)." The monitoring system immediately issued an alarm and accurately located the information. Maintenance personnel can directly proceed to designated sections for troubleshooting, avoiding blind inspections and greatly improving processing speed and safety. This invention combines "high-frequency impedance monitoring" with "passive tag positioning" to provide an unprecedented proactive, accurate, and safe online monitoring solution for open-circuit faults in the secondary circuits of CTs in the complex environment of hydropower stations.

[0046] This concludes the embodiment.

[0047] like Figure 2 As shown, a second aspect of the present invention is to provide a power system CT secondary circuit open circuit detection system with signal injection, comprising: Signal injection module 101: used to pre-set passive resonant tags at multiple key nodes along the secondary circuit of the current transformer, each passive resonant tag having a unique corresponding resonant frequency; set several monitoring points in the secondary circuit of the current transformer, and inject a high-frequency constant current source signal of a specific frequency at the monitoring points of the secondary circuit of the current transformer, the frequency of the high-frequency constant current source signal being higher than the power frequency and the amplitude being in the milliampere range; Adaptive threshold adjustment module 102: used to detect the loop input impedance corresponding to the high-frequency constant current source signal at the monitoring point; adjust the benchmark preset alarm threshold according to changes in ambient temperature and equipment aging to obtain the adjusted alarm threshold; when the magnitude of the loop input impedance is greater than the adjusted alarm threshold, it is determined that an open circuit fault has occurred in the secondary circuit of the current transformer. Fault feature scanning and identification module 103: After determining an open circuit fault, it starts a frequency sweep mode and injects a continuously changing scanning signal into the circuit; during the frequency sweep, it detects whether an impedance dip occurs, and when an impedance dip occurs, it determines the corresponding characteristic frequency; wherein, the characteristic frequency is the resonant frequency of the passive resonant tag. Fault section precise location module 104: It is used to determine the section where the open circuit fault point is located by querying the preset "passive resonant tag-fault section" mapping relationship based on the detected characteristic frequency.

[0048] A third aspect of the present invention is to provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a signal injection method for detecting open circuits in the secondary circuit of a power system CT.

[0049] A fourth aspect of the present invention is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements a signal-injected method for detecting open circuits in the secondary circuit of a power system CT.

[0050] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, etc.) containing computer-usable program code.

[0051] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0052] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0053] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for detecting open circuits in the secondary circuit of a power system CT using signal injection, characterized in that, include: Passive resonant tags are pre-set at multiple key nodes along the secondary circuit of the current transformer, each of which has a unique resonant frequency; several monitoring points are set in the secondary circuit of the current transformer, and a high-frequency constant current source signal of a specific frequency is injected into the monitoring points of the secondary circuit of the current transformer. The frequency of the high-frequency constant current source signal is higher than the power frequency, and the amplitude is in the milliampere range. At the monitoring point, the circuit input impedance corresponding to the high-frequency constant current source signal is detected; the baseline preset alarm threshold is adjusted by changes in ambient temperature and the degree of equipment aging to obtain the adjusted alarm threshold; when the magnitude of the circuit input impedance is greater than the adjusted alarm threshold, it is determined that an open circuit fault has occurred in the secondary circuit of the current transformer. After determining an open circuit fault, a frequency sweep mode is initiated, injecting a continuously varying scanning signal into the circuit. During the frequency sweep, the impedance dip is detected, and when an impedance dip occurs, the corresponding characteristic frequency is determined. The characteristic frequency is the resonant frequency of the passive resonant tag. Based on the detected characteristic frequency, the preset "passive resonant tag-fault section" mapping relationship is queried to determine the section where the open circuit fault point is located.

2. The method for detecting open circuits in the secondary circuit of a power system CT by signal injection according to claim 1, characterized in that, The process of adjusting the baseline preset alarm threshold based on changes in ambient temperature and the degree of equipment aging to obtain the adjusted alarm threshold includes: The first adjustment factor for obtaining the alarm threshold is based on the ambient temperature; A second adjustment factor for the alarm threshold is obtained based on the degree of equipment aging trend. The baseline preset alarm threshold is adjusted based on the first adjustment factor and the second adjustment factor of the alarm threshold to obtain the adjusted alarm threshold.

3. The method for detecting open circuits in the secondary circuit of a power system CT by signal injection according to claim 2, characterized in that, The first adjustment factor for obtaining the alarm threshold based on ambient temperature is specifically expressed by the formula: In the formula, This represents the average ambient temperature across all times within the reference window at each given moment. Indicates the reference ambient temperature. The first adjustment factor represents the alarm threshold. Represents a linear normalization function; The baseline ambient temperature is a preset value, and the reference window for each moment is a window with a length of five moments before and after it.

4. The method for detecting open circuits in the secondary circuit of a power system CT by signal injection according to claim 2, characterized in that, The second adjustment factor for obtaining the alarm threshold based on the degree of equipment aging is specifically expressed by the formula: In the formula, The second adjustment factor represents the alarm threshold. This represents the current long-term impedance trend value predicted by the trend analysis algorithm. Indicates the drift tracking coefficient. This represents the reference impedance at the initial commissioning of the system; Indicates the safety boundary value. This is an activation function used for data normalization. The drift tracking coefficient and safety boundary value are preset values.

5. The method for detecting open circuits in the secondary circuit of a power system CT by signal injection according to claim 2, characterized in that, The baseline preset alarm threshold is adjusted according to the first adjustment factor and the second adjustment factor of the alarm threshold to obtain the adjusted alarm threshold, which is specifically expressed by the formula: In the formula, The first adjustment factor represents the alarm threshold. The second adjustment factor represents the alarm threshold. Indicates the baseline preset alarm threshold. This indicates the adjusted alarm threshold.

6. The method for detecting open circuits in the secondary circuit of a power system CT by signal injection according to claim 1, characterized in that, The section where the open-circuit fault point is located is specifically: If the resonant frequency of the Nth passive resonant tag is detected, but the resonant frequencies of the (N+1)th and subsequent passive resonant tags are not detected, then the open circuit point is determined to be between the Nth and (N+1)th passive resonant tags.

7. The method for detecting open circuits in the secondary circuit of a power system CT by signal injection according to claim 1, characterized in that, The frequency range of the high-frequency constant current source signal is from 1 kHz to 100 kHz.

8. A power system CT secondary circuit open circuit detection system with signal injection, characterized in that, include: Signal injection module: used to pre-set passive resonant tags at multiple key nodes along the secondary circuit of the current transformer, each passive resonant tag having a unique corresponding resonant frequency; set several monitoring points in the secondary circuit of the current transformer, and inject a high-frequency constant current source signal of a specific frequency at the monitoring points of the secondary circuit of the current transformer, the frequency of the high-frequency constant current source signal being higher than the power frequency and the amplitude being in the milliampere range; Adaptive threshold adjustment module: used to detect the loop input impedance corresponding to the high-frequency constant current source signal at the monitoring point; adjust the benchmark preset alarm threshold according to changes in ambient temperature and equipment aging to obtain the adjusted alarm threshold; when the magnitude of the loop input impedance is greater than the adjusted alarm threshold, it is determined that an open circuit fault has occurred in the secondary circuit of the current transformer. Fault Feature Scanning and Identification Module: After determining an open circuit fault, it initiates a frequency sweep mode and injects a continuously changing scanning signal into the circuit; during the frequency sweep, it detects whether an impedance dip occurs, and when an impedance dip occurs, it determines the corresponding characteristic frequency; wherein, the characteristic frequency is the resonant frequency of the passive resonant tag. Fault Section Precise Location Module: Based on the detected characteristic frequency, this module queries the preset "passive resonant tag-fault section" mapping relationship to determine the section where the open circuit fault point is located.

9. An electronic device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the signal injection method for detecting open circuits in the secondary circuit of a power system CT as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the signal injection power system CT secondary circuit open circuit detection method according to any one of claims 1-7.

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