CVT low-voltage terminal ungrounded defect identification method and device, electronic equipment and storage medium
By acquiring and analyzing the secondary voltage waveform signal of CVT and combining the comprehensive judgment of multiple voltage characteristics, the problem of difficult to identify the ungrounded defect of the CVT low-voltage terminal is solved, and the safety and stability of the power grid are improved.
Patent Information
- Application Number
- CN202510187173.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-05-27
Smart Images
Figure CN120044462A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of device detection, and particularly to a method, device, electronic device and storage medium for identifying the defect of ungrounded low-voltage terminal of a CVT. Background Art
[0002] A capacitive voltage transformer (hereinafter referred to as CVT) is an important device used for voltage monitoring in a power system. Its main function is to provide accurate voltage signals for relay protection, metering and measurement. The CVT has a complex structure and is usually composed of a capacitive voltage divider, an electromagnetic unit, etc. Its operating state is directly related to the stability and accuracy of the secondary voltage. Once a defect occurs inside the CVT, its transfer characteristics will be affected, resulting in abnormal secondary voltage, unable to truly reflect the actual waveform of the system, and even possibly causing safety problems such as misoperation of relay protection and measurement deviation.
[0003] Among various defect types of CVTs, the defect of ungrounded low-voltage terminal is a relatively common and easily overlooked fault type. After the equipment is put into operation, the ungrounded low-voltage terminal may generate long-term discharge phenomena, causing the secondary terminal to burn out or the relay protection device to malfunction, thus leading to more serious potential safety hazards. Compared with other CVT defects, the identification of the defect of ungrounded low-voltage terminal is more difficult. The defect of ungrounded low-voltage terminal usually occurs in the low-voltage terminal part of the CVT, which is relatively hidden during the normal operation of power equipment and is not easily directly observed or detected. The defect is often due to the failure to restore grounding after maintenance or testing, and usually has no obvious external manifestations, resulting in difficulty in timely discovery through traditional inspection methods. Existing CVT defect monitoring technologies mostly focus on the fault diagnosis of components such as capacitive voltage dividers and electromagnetic units, and have not covered the monitoring and diagnosis requirements of this special defect, affecting the safety and stability of the power grid. Summary of the Invention
[0004] Embodiments of the present invention provide a method, device, electronic device and storage medium for identifying the defect of ungrounded low-voltage terminal of a CVT. By implementing the present invention, the defect of ungrounded low-voltage terminal of a CVT can be effectively identified, thereby improving the safety and stability of the power grid.
[0005] An embodiment of the present invention provides a method for identifying the defect of ungrounded low-voltage terminal of a CVT, including:
[0006] Obtaining the secondary voltage waveform signal of the CVT to be defect-identified and the secondary voltage waveform signal of the in-phase CVT; wherein, the in-phase CVT is a CVT that is installed at a different position in the substation from the CVT to be defect-identified but belongs to the same phase; and there is no defect in the in-phase CVT;
[0007] In the case of a voltage mutation in the CVT to be defect-identified, based on the secondary voltage waveform signal of the in-phase CVT, determine whether there is an internal defect in the CVT to be defect-identified;
[0008] Based on the secondary voltage waveform signal of the CVT to be defect-identified, determine whether there is a peak distortion in the CVT to be defect-identified;
[0009] Based on the secondary voltage waveform signal of the CVT to be defect-identified, calculate and generate a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation, and determine whether there is a charge-discharge defect in the CVT to be defect-identified according to the first voltage integral value and the second voltage integral value;
[0010] Based on a preset fundamental wave amplitude range, a preset harmonic content threshold, and the secondary voltage waveform signal of the CVT to be defect-identified, determine whether there are abnormalities in the fundamental wave amplitude and harmonics in the CVT to be defect-identified;
[0011] In the case where the CVT to be defect-identified has an internal defect, has a peak distortion, has no charge-discharge defect, has an abnormal fundamental wave amplitude, and has harmonic abnormalities, determine that the CVT to be defect-identified has a defect of ungrounded low-voltage terminal, otherwise determine that the CVT to be defect-identified has no defect of ungrounded low-voltage terminal.
[0012] Furthermore, determine whether there is a voltage mutation in the CVT to be defect-identified through the following method:
[0013] Based on a preset time window, determine whether the voltage amplitude change amount of the secondary voltage waveform signal of the CVT to be defect-identified within any time window exceeds a preset voltage mutation threshold. If so, determine that the CVT to be defect-identified has a voltage mutation. If not, determine that the CVT to be defect-identified has no voltage mutation.
[0014] Furthermore, the step of, in the case of a voltage mutation in the CVT to be defect-identified, based on the secondary voltage waveform signal of the in-phase CVT, determining whether there is an internal defect in the CVT to be defect-identified includes:
[0015] Based on a preset time window, determine whether the voltage amplitude change amount of the secondary voltage waveform signal of the in-phase CVT within any time window exceeds a preset voltage mutation threshold. If so, determine that the in-phase CVT has a voltage mutation. If not, determine that the in-phase CVT has no voltage mutation;
[0016] In the case where the in-phase CVT has a voltage mutation, determine that the CVT to be defect-identified has no internal defect;
[0017] In the case where the in-phase CVT has no voltage mutation, determine that the CVT to be defect-identified has an internal defect.
[0018] Further, determining whether there is a peak distortion in the CVT to be defect-identified according to the secondary voltage waveform signal of the CVT to be defect-identified includes:
[0019] According to the secondary voltage waveform signal of the CVT to be defect-identified, extract the positions of voltage mutations and the target voltage amplitudes of a preset number of sampling points before and after the zero-crossing points;
[0020] Judge whether the positions of voltage mutations in the CVT to be defect-identified are only located at the peaks. If not, judge that there is no peak distortion in the CVT to be defect-identified; if so, judge whether each target voltage amplitude is 0;
[0021] When each target voltage amplitude is 0, determine that there is no peak distortion in the CVT to be defect-identified;
[0022] When there is a target voltage amplitude that is not 0, determine that there is a peak distortion in the CVT to be defect-identified.
[0023] Further, calculating a first voltage integral value before voltage mutation and a second voltage integral value after voltage mutation according to the secondary voltage waveform signal of the CVT to be defect-identified, and judging whether there is a charge-discharge defect in the CVT to be defect-identified according to the first voltage integral value and the second voltage integral value includes:
[0024] According to the secondary voltage waveform signal of the CVT to be defect-identified, calculate a first voltage integral value within a preset period before voltage mutation and a second voltage integral value within a preset period after voltage mutation;
[0025] Calculate the absolute difference between the first voltage integral value and the second voltage integral value to generate an integral difference;
[0026] Judge whether the integral difference exceeds a preset local distortion threshold. If so, determine that there is a charge-discharge defect in the CVT to be defect-identified; if not, determine that there is no charge-discharge defect in the CVT to be defect-identified.
[0027] Further, judging whether there is a fundamental wave amplitude abnormality and a harmonic abnormality in the CVT to be defect-identified according to a preset fundamental wave amplitude interval, a preset harmonic content threshold, and the secondary voltage waveform signal of the CVT to be defect-identified includes:
[0028] Perform a Fourier transform on the secondary voltage waveform signal of the CVT to be defect-identified to obtain the spectral information after Fourier transform;
[0029] Extract and generate the fundamental wave amplitude and the harmonic amplitude from the spectral information;
[0030] Determine whether the fundamental wave amplitude of the CVT to be defect-identified is within a preset fundamental wave amplitude range. If so, determine that the CVT to be defect-identified has no abnormal fundamental wave amplitude. If not, determine that the CVT to be defect-identified has an abnormal fundamental wave amplitude;
[0031] Calculate and generate the harmonic content of the CVT to be defect-identified based on the harmonic amplitude and the fundamental wave amplitude;
[0032] Determine whether the harmonic content of the CVT to be defect-identified exceeds a preset harmonic content threshold. If so, determine that the CVT to be defect-identified has harmonic anomalies. If not, determine that the CVT to be defect-identified has no harmonic anomalies.
[0033] Furthermore, the method for identifying the defect of the ungrounded low-voltage terminal of the CVT further includes:
[0034] When there is no voltage mutation in the CVT to be defect-identified, determine that the CVT to be defect-identified has no defect of the ungrounded low-voltage terminal.
[0035] Based on the above method embodiments, the present invention correspondingly provides device embodiments.
[0036] An embodiment of the present invention provides an identification device for the defect of the ungrounded low-voltage terminal of a CVT, including: a data acquisition module, an internal defect determination module, a crest distortion determination module, a charge and discharge defect determination module, a fundamental wave amplitude anomaly and harmonic anomaly module, and an ungrounded low-voltage terminal defect determination module;
[0037] The data acquisition module is used to acquire the secondary voltage waveform signal of the CVT to be defect-identified and the secondary voltage waveform signal of the in-phase CVT; wherein, the in-phase CVT is a CVT that is installed at a different position in the substation from the CVT to be defect-identified but belongs to the same phase; the in-phase CVT has no defects;
[0038] The internal defect determination module is used to determine whether the CVT to be defect-identified has internal defects according to the secondary voltage waveform signal of the in-phase CVT when there is a voltage mutation in the CVT to be defect-identified;
[0039] The crest distortion determination module is used to determine whether the CVT to be defect-identified has crest distortion according to the secondary voltage waveform signal of the CVT to be defect-identified;
[0040] The charge and discharge defect determination module is used to calculate and generate a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation according to the secondary voltage waveform signal of the CVT to be defect-identified, and determine whether the CVT to be defect-identified has charge and discharge defects according to the first voltage integral value and the second voltage integral value;
[0041] The fundamental wave amplitude anomaly and harmonic anomaly module is used to determine whether there are fundamental wave amplitude anomalies and harmonic anomalies in the CVT to be defect-identified according to a preset fundamental wave amplitude range, a preset harmonic content threshold, and the secondary voltage waveform signal of the CVT to be defect-identified;
[0042] The low-voltage terminal ungrounded defect determination module is used to determine that the CVT to be defect-identified has a low-voltage terminal ungrounded defect when the CVT to be defect-identified has internal defects, has peak distortion, does not have charge-discharge defects, has a fundamental wave amplitude anomaly and has a harmonic anomaly, otherwise it is determined that the CVT to be defect-identified does not have a low-voltage terminal ungrounded defect.
[0043] Based on the above method item embodiments, the present invention correspondingly provides an electronic device item embodiment.
[0044] An embodiment of the present invention provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method for identifying the ungrounded defect of the low-voltage terminal of the CVT described in any one of the above method item embodiments can be implemented.
[0045] Based on the above method item embodiments, the present invention correspondingly provides a storage medium item embodiment.
[0046] An embodiment of the present invention provides a storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method for identifying the ungrounded defect of the low-voltage terminal of the CVT described in any one of the above method item embodiments can be implemented.
[0047] Compared with the prior art, the present invention has the following beneficial effects:
[0048] An embodiment of the present invention provides a method, device, electronic device, and storage medium for identifying the defect of ungrounded low-voltage terminals of a CVT. The method acquires the secondary voltage waveform signals of the CVT to be defect-identified and the in-phase CVT, where the in-phase CVT is installed at different positions in the substation and has no defects. Through comparison, when a voltage mutation occurs in the CVT to be defect-identified, the waveform signal of the in-phase CVT is used to determine whether there are internal defects. By extracting the voltage waveform features, focusing on identifying the peak distortion, and judging whether the local oscillation of the waveform is concentrated in the peak region. Subsequently, the integral value difference before and after the voltage mutation is calculated to distinguish the defect types and exclude the possibility of periodic charge and discharge defects. In addition, the fundamental wave amplitude and harmonic content are extracted according to the Fourier transform, and compared with the preset threshold values to judge the abnormal fundamental wave amplitude and harmonic abnormalities. Combining the comprehensive judgment logic of internal defects, peak distortion, charge and discharge defects, abnormal fundamental wave amplitude, and harmonic abnormalities, if specific conditions are met, it is determined that the CVT to be defect-identified has the defect of ungrounded low-voltage terminals. The present invention effectively solves the problem of difficult identification of the defect of ungrounded low-voltage terminals by acquiring the secondary voltage waveform signals of the CVT to be defect-identified and the in-phase defect-free CVT, and combining the comprehensive judgments of voltage mutation, peak distortion, charge and discharge defects, abnormal fundamental wave amplitude, and harmonic abnormalities. This method makes full use of in-phase comparison and various feature analyses to ensure the accuracy and reliability of the diagnosis, thereby improving the safety and stability of the power grid operation. BRIEF DESCRIPTION OF THE DRAWINGS
[0049] Figure 1 FIG. is a schematic flow chart of a method for identifying the defect of ungrounded low-voltage terminals of a CVT provided by an embodiment of the present invention.
[0050] Figure 2 FIG. is a measured diagram of the secondary voltage waveform of a CVT with the defect of ungrounded low-voltage terminals provided by an embodiment of the present invention.
[0051] Figure 3 FIG. is a simulation diagram of the secondary voltage waveform of a CVT with the defect of ungrounded low-voltage terminals provided by an embodiment of the present invention.
[0052] Figure 4 FIG. is a schematic structural diagram of a device for the defect of ungrounded low-voltage terminals of a CVT provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0053] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0054] AsFigure 1 As shown in the figure, an embodiment of the present invention provides a method for identifying the defect of ungrounded low-voltage terminals of a CVT, which at least includes the following steps:
[0055] Step S1: Obtain the secondary voltage waveform signal of the CVT to be defect-identified and the secondary voltage waveform signal of the in-phase CVT; wherein, the in-phase CVT is a CVT that is installed at different positions in the substation but belongs to the same phase as the CVT to be defect-identified; there is no defect in the in-phase CVT.
[0056] In a preferred embodiment, the following method is used to determine whether there is a voltage mutation in the CVT to be defect-identified:
[0057] According to a preset time window, judge whether the voltage amplitude change amount of the secondary voltage waveform signal of the CVT to be defect-identified within any time window exceeds a preset voltage mutation threshold. If so, it is determined that there is a voltage mutation in the CVT to be defect-identified; if not, it is determined that there is no voltage mutation in the CVT to be defect-identified.
[0058] In specific implementation, the in-phase CVT is usually a CVT device of the same phase installed on different buses or outgoing lines in the substation. Its system conditions for connecting with the CVT to be defect-identified are similar, and it can provide an effective reference voltage signal. To ensure the reliability and accuracy of the data, it is necessary to monitor and obtain the secondary voltage waveform signals of the CVT to be defect-identified and the in-phase CVT in the substation in real time. The sampling rate should meet the requirements for high-frequency signal acquisition and not be lower than a certain level, such as 5 MHz, to ensure capturing the detailed features of the voltage waveform, thereby providing a high-precision analysis basis for subsequent defect identification.
[0059] Step S2: In the case where there is a voltage mutation in the CVT to be defect-identified, judge whether there is an internal defect in the CVT to be defect-identified according to the secondary voltage waveform signal of the in-phase CVT.
[0060] In a preferred embodiment, the step of judging whether there is an internal defect in the CVT to be defect-identified according to the secondary voltage waveform signal of the in-phase CVT in the case where there is a voltage mutation in the CVT to be defect-identified includes:
[0061] According to a preset time window, judge whether the voltage amplitude change amount of the secondary voltage waveform signal of the in-phase CVT within any time window exceeds a preset voltage mutation threshold. If so, it is determined that there is a voltage mutation in the in-phase CVT; if not, it is determined that there is no voltage mutation in the in-phase CVT;
[0062] In the case where there is a voltage mutation in the in-phase CVT, it is determined that there is no internal defect in the CVT to be defect-identified;
[0063] In the case where there is no voltage mutation in the in-phase CVT, it is determined that the CVT to be defect-identified has an internal defect.
[0064] Specifically, through a high-precision sampling device, such as a sampling rate reaching 5 MHz or higher, fine-grained sampling is performed on the secondary voltage waveform of the CVT to be defect-identified, and the voltage amplitude change data of multiple consecutive sampling points is extracted. The system sets a change threshold for voltage mutation, such as 2 V, to identify significant changes in the voltage waveform within a short period. If the voltage amplitude change exceeds the preset threshold within a specified time window or among consecutive sampling points, it is regarded as a voltage waveform mutation.
[0065] Meanwhile, the system compares the signal characteristics of the secondary voltage waveforms of other CVTs installed in the same phase. These in-phase CVTs are located at different positions, such as different busbars or outgoing lines, but belong to the same phase and are considered to be operating normally without defects. If no significant abnormalities are found in the waveform signals of other CVTs in the same phase during the voltage waveform mutation detection, and only the secondary voltage waveform of the CVT to be defect-identified shows a mutation, it can be clearly inferred that the abnormality originates from the internal defect or abnormal operating state of the CVT to be defect-identified, rather than being caused by external system factors such as transient overvoltage and load changes. This comparative analysis can significantly enhance the pertinence and accuracy of the judgment.
[0066] It can be understood that it is required to compare the CVTs in the same phase installed at different positions. If a voltage mutation occurs in the CVT to be defect-identified, it indicates that the defect is due to the problem of the CVT itself rather than an external system problem.
[0067] Step S3: According to the secondary voltage waveform signal of the CVT to be defect-identified, determine whether there is a peak distortion in the CVT to be defect-identified.
[0068] In a preferred embodiment, the determining whether there is a peak distortion in the CVT to be defect-identified according to the secondary voltage waveform signal of the CVT to be defect-identified includes:
[0069] According to the secondary voltage waveform signal of the CVT to be defect-identified, extract the position of the voltage mutation and the target voltage amplitudes of a preset number of sampling points before and after the zero-crossing point;
[0070] Judge whether the position of the voltage mutation of the CVT to be defect-identified is only located at the peak. If not, judge that the CVT to be defect-identified has no peak distortion; if so, judge whether each target voltage amplitude is 0;
[0071] In the case where each target voltage amplitude is 0, it is determined that the CVT to be defect-identified has no peak distortion;
[0072] In the case where there is a target voltage amplitude that is not 0, it is determined that the CVT to be defect-identified has a peak distortion.
[0073] In a specific implementation, based on the secondary voltage waveform signal of the CVT to be defect-identified, the positions of voltage mutations and the target voltage amplitudes of a preset number of sampling points before and after the zero-crossing point are extracted, and the positions of voltage mutations are analyzed emphatically to determine whether they occur only in the peak region of the waveform. If the voltage mutations do not concentrate in the peaks but appear at other positions, especially near the zero-crossing point, it can be directly determined that the CVT to be defect-identified has no peak distortion; if the mutations are indeed only located in the peak region, the voltage amplitude characteristics of the target sampling points before and after the zero-crossing point need to be further analyzed. If the target voltage amplitudes of several sampling points before and after the zero-crossing point are all non-zero, it indicates that the waveform remains continuous at the zero-crossing point, and the mutation at the peak may be caused by other factors, so it can be determined that there is peak distortion; but if the target voltage amplitudes of the sampling points are all zero, it indicates that there may be an interruption phenomenon caused by discharge at the peak, so it can be determined that the CVT to be defect-identified has no peak distortion.
[0074] It should be noted that poor contact defects can cause waveform distortion, but the distortion positions caused by poor contact at different positions are different. The typical characteristic of the defect that the low-voltage terminal of this type of CVT is not grounded is that there is waveform distortion at the peak, but the distortion is local. When the position of poor contact is connected through arc discharge, the waveform returns to normal. In addition, different from the defect of poor contact in the circuit, the waveform of this type of defect is smooth and has no interruption phenomenon at the zero-crossing point. Therefore, the waveform is required to be continuous at the zero-crossing point.
[0075] Step S4: According to the secondary voltage waveform signal of the CVT to be defect-identified, calculate and generate a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation, and determine whether the CVT to be defect-identified has charge-discharge defects according to the first voltage integral value and the second voltage integral value.
[0076] In a preferred embodiment, the step of calculating and generating a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation according to the secondary voltage waveform signal of the CVT to be defect-identified, and determining whether the CVT to be defect-identified has charge-discharge defects according to the first voltage integral value and the second voltage integral value includes:
[0077] According to the secondary voltage waveform signal of the CVT to be defect-identified, calculate and generate a first voltage integral value within a preset period before the voltage mutation and a second voltage integral value within a preset period after the voltage mutation;
[0078] Calculate the absolute difference between the first voltage integral value and the second voltage integral value to generate an integral difference;
[0079] Determine whether the integral difference exceeds a preset local distortion threshold. If so, determine that the CVT to be defect-identified has charge-discharge defects; if not, determine that the CVT to be defect-identified has no charge-discharge defects.
[0080] Exemplarily, according to the secondary voltage waveform signal of the CVT to be defect-identified, one preset period (such as 1 / 4 power frequency period or a complete period) before and after the voltage mutation is selected as the analysis window, and the first voltage integral value within the preset period before the voltage mutation and the second voltage integral value within the preset period after the voltage mutation are calculated and generated respectively. These integral values are obtained by accumulating or summing the amplitudes of the waveform within this time period, thus reflecting the cumulative change of the waveform energy.
[0081] Then, calculate the absolute difference between the first voltage integral value and the second voltage integral value to generate an integral difference. This difference reflects the degree of change in the energy distribution within the same time period before and after the voltage waveform mutation. To ensure the accuracy of the analysis, high-frequency interference signals can be filtered during the integral calculation process, and at the same time, the sampling rate should be high enough, such as 5 MHz, to capture fine waveform features.
[0082] Next, determine whether the integral difference exceeds a preset local distortion threshold. For example, a threshold range set based on historical data or actual experience, such as 5% or lower. If the integral difference exceeds the preset threshold, it can be determined that the CVT to be defect-identified has a charge-discharge defect, indicating a significant impact on the abnormal operating state of its secondary voltage signal; if the integral difference does not exceed the preset threshold, it can be determined that the CVT to be defect-identified does not have a charge-discharge defect, indicating that the overall fluctuation of its secondary voltage signal is small and not affected by obvious abnormalities.
[0083] It should be noted that there are significant differences between periodic charge-discharge defects and other types of defects. Specifically, periodic charge-discharge defects usually cause overall distortion of the entire waveform. For example, there are multiple voltage abnormalities or obvious amplitude fluctuations within the waveform period. The defect of the ungrounded low-voltage terminal of the CVT mainly shows local distortion of the waveform, especially voltage abnormalities at specific moments or specific positions of the waveform (such as peaks or valleys). This local feature makes the change in the voltage integral value between the normal section and the abnormal section of the waveform relatively small, while periodic charge-discharge defects will significantly affect the integral value difference of the entire waveform. Therefore, by comparing the change in the voltage integral value within a short period before and after the mutation, the defect of the ungrounded low-voltage terminal and periodic charge-discharge defects can be effectively distinguished, thereby improving the accuracy of diagnosis.
[0084] Step S5: According to the preset fundamental wave amplitude range, the preset harmonic content threshold, and the secondary voltage waveform signal of the CVT to be defect-identified, determine whether the CVT to be defect-identified has abnormal fundamental wave amplitude and abnormal harmonics.
[0085] In a preferred embodiment, determining whether there are abnormalities in the fundamental wave amplitude and harmonics of the CVT to be defect-identified according to a preset fundamental wave amplitude range, a preset harmonic content threshold, and the secondary voltage waveform signal of the CVT to be defect-identified includes:
[0086] Perform a Fourier transform on the secondary voltage waveform signal of the CVT to be defect-identified to obtain the spectral information after the Fourier transform;
[0087] Extract and generate the fundamental wave amplitude and harmonic amplitudes from the spectral information;
[0088] Determine whether the fundamental wave amplitude of the CVT to be defect-identified is within the preset fundamental wave amplitude range. If so, determine that there is no abnormality in the fundamental wave amplitude of the CVT to be defect-identified. If not, determine that there is an abnormality in the fundamental wave amplitude of the CVT to be defect-identified;
[0089] Calculate and generate the harmonic content of the CVT to be defect-identified based on the harmonic amplitude and the fundamental wave amplitude;
[0090] Determine whether the harmonic content of the CVT to be defect-identified exceeds the preset harmonic content threshold. If so, determine that there is a harmonic abnormality in the CVT to be defect-identified. If not, determine that there is no harmonic abnormality in the CVT to be defect-identified.
[0091] Exemplarily, the harmonic content of the CVT to be defect-identified is calculated by the following formula:
[0092]
[0093] where THD is the harmonic content of the CVT to be defect-identified; V 1 is the fundamental wave amplitude; V i (i≠1) is the harmonic amplitude numbered i; n is the serial number of the harmonic amplitude.
[0094] In a specific implementation, perform a Fourier transform on the secondary voltage waveform signal of the CVT to be defect-identified, decompose it into multiple frequency components, and obtain the spectral information after the Fourier transform. This spectral information includes the amplitudes and phases of each frequency component and can intuitively reflect the energy distribution of the secondary voltage waveform in the frequency domain.
[0095] Extract the fundamental wave (usually 50Hz) amplitude and the amplitudes of the main low-order harmonics (such as the 3rd and 5th harmonics) from the spectral information. For the extraction of harmonic amplitudes, key harmonic frequency components that may affect the stability of the power grid can be analyzed focus to ensure the accuracy of the results.
[0096] Determine whether the fundamental wave amplitude of the CVT to be defect-identified is within a preset fundamental wave amplitude range. This range is usually set based on actual operating experience or specification requirements. For example, the fundamental wave amplitude does not exceed 1.5 times the rated value (such as 1.5 times the overvoltage value). If the fundamental wave amplitude is within the range, it is determined that the CVT to be defect-identified has no abnormal fundamental wave amplitude; if it exceeds the range, it is determined that the CVT to be defect-identified has an abnormal fundamental wave amplitude.
[0097] According to the extracted harmonic amplitude and fundamental wave amplitude, calculate the harmonic content of the CVT to be defect-identified. Usually, the total harmonic distortion rate (THD) or the ratio of a specific sub-harmonic to the fundamental wave amplitude is used to measure it.
[0098] Determine whether the harmonic content of the CVT to be defect-identified exceeds a preset harmonic content threshold. For example, it is stipulated that the harmonic contents of the 3rd and 5th harmonics do not exceed 4% respectively. If the harmonic content does not exceed the threshold, it is determined that the CVT to be defect-identified has no harmonic abnormality; if the harmonic content exceeds the standard, it is determined that the CVT to be defect-identified has a harmonic abnormality.
[0099] It can be understood that through spectrum analysis of the secondary voltage waveform signal, if the main frequency is clearly 50Hz and there is no significant low-frequency component interference, the possibility of the existence of low-frequency components in the system voltage can be excluded. This indicates that there is no frequency disturbance in the system, and the operating voltage frequency of the CVT conforms to the normal operating range. When the main frequency is 50Hz, the fundamental wave amplitude is detected. If its amplitude meets the requirement of the overvoltage multiple (for example, it does not exceed 1.5 times the rated voltage), it means that the CVT is not in an overvoltage operating state. Overvoltage will cause the CVT iron core to saturate, resulting in distortion of the secondary waveform and non-linear transmission characteristics, while the normal fundamental wave amplitude indicates that there is no such saturation phenomenon. Calculate the harmonic content to ensure that it does not exceed the preset threshold. A lower harmonic content indicates that the system is not affected by external electromagnetic interference and there is no harmonic distortion problem caused by load non-linearity. In particular, the amplitudes of low-order harmonics (such as the 3rd and 5th harmonics) should be strictly controlled to avoid instability and misdiagnosis caused by harmonics.
[0100] Step S6: When the CVT to be defect-identified has internal defects, has peak distortion, has no charge-discharge defects, has an abnormal fundamental wave amplitude, and has a harmonic abnormality, determine that the CVT to be defect-identified has a defect that the low-voltage terminal is not grounded; otherwise, determine that the CVT to be defect-identified has no defect that the low-voltage terminal is not grounded.
[0101] In a preferred embodiment, the method for identifying the defect that the low-voltage terminal of the CVT is not grounded further includes: when there is no voltage mutation in the CVT to be defect-identified, determine that the CVT to be defect-identified has no defect that the low-voltage terminal is not grounded.
[0102] It is understandable that, on the basis of the presence of internal defects in the CVT to be defect-identified, by comprehensively analyzing its characteristics such as peak distortion, charge-discharge defects, fundamental wave amplitude abnormality, and harmonic abnormality, and through the cross-verification of these multi-dimensional indicators, the nature of the defects in the CVT to be defect-identified is judged. When there are mutations in the peak region of the secondary voltage waveform signal, the local waveform characteristics are significantly different from the normal state, and the fundamental wave amplitude deviates from the preset range, and at the same time the harmonic content exceeds the threshold, it indicates that the CVT may have serious electrical characteristic abnormalities. In this case, if all the abnormal characteristics are satisfied simultaneously, it can be further determined that the abnormality originates from the defect of the low-voltage terminal not being grounded, rather than other types of faults or external condition influences. This diagnostic method effectively utilizes the complementarity and correlation of different characteristics, improving the accuracy and reliability of identifying the defect of the low-voltage terminal not being grounded. If the above characteristics are not all satisfied, it can be judged that the CVT to be defect-identified does not have the defect of the low-voltage terminal not being grounded.
[0103] As Figure 2 shown, the present invention provides an actual measurement diagram of the secondary voltage waveform of a CVT with a defect of the low-voltage terminal not being grounded; as Figure 3 shown, the present invention provides a simulation diagram of the secondary voltage waveform of a CVT with a defect of the low-voltage terminal not being grounded;
[0104] From Figure 2 and Figure 3 it can be seen that whether it is the measured data or the simulation result, when there is a defect of the low-voltage terminal not being grounded in this secondary voltage waveform, it is significantly different from the steady-state amplitude change characteristics caused by the defects of the capacitive voltage divider and short-circuit defects. Further observing the waveform characteristics, it can be found that this defect does not significantly change the overall shape of the waveform, the voltage waveform still maintains the basic sine wave shape, and the harmonic content is low, indicating that the main frequency and harmonic components of the waveform are within the normal range. Most significantly, the defect is mainly manifested as local oscillations occurring at the waveform peak, and near the zero-crossing point, the waveform does not undergo distortion, which is significantly different from the waveform manifestations of other types of defects.
[0105] Combined with the foregoing judgment conditions, through the comprehensive analysis of peak distortion, charge-discharge defects, fundamental wave amplitude, and harmonic abnormality, the presence of this defect can be accurately identified. In particular, when it is detected that the voltage mutation only occurs in the peak region, and the waveform characteristics at the zero-crossing point are continuous and smooth, it is further confirmed that this defect is the defect of the low-voltage terminal not being grounded, rather than an electrical problem caused by other external factors. By this method, the defect of the low-voltage terminal not being grounded is identified in a timely and accurate manner, avoiding the equipment running in a defective state for a long time, preventing a series of chain reactions such as repeated arcing at the grounding point resulting in equipment ablation and reduced sealing performance, thereby effectively reducing the risk of equipment damage and ensuring the safety and stability of the power system.
[0106] Based on the above method embodiment, the present invention correspondingly provides a device embodiment.
[0107] As Figure 4 shown, an embodiment of the present invention provides a recognition device for the defect of ungrounded low-voltage terminal of a CVT, including: a data acquisition module, an internal defect determination module, a crest distortion determination module, a charge and discharge defect determination module, a fundamental wave amplitude anomaly and harmonic anomaly module, and an ungrounded low-voltage terminal defect determination module;
[0108] The data acquisition module is configured to acquire the secondary voltage waveform signal of the CVT to be defect-recognized and the secondary voltage waveform signal of the in-phase CVT; wherein, the in-phase CVT is a CVT that is installed at a different position in the substation from the CVT to be defect-recognized but belongs to the same phase; there is no defect in the in-phase CVT;
[0109] The internal defect determination module is configured to, when there is a voltage mutation in the CVT to be defect-recognized, determine whether there is an internal defect in the CVT to be defect-recognized according to the secondary voltage waveform signal of the in-phase CVT;
[0110] The crest distortion determination module is configured to determine whether there is a crest distortion in the CVT to be defect-recognized according to the secondary voltage waveform signal of the CVT to be defect-recognized;
[0111] The charge and discharge defect determination module is configured to calculate and generate a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation according to the secondary voltage waveform signal of the CVT to be defect-recognized, and determine whether there is a charge and discharge defect in the CVT to be defect-recognized according to the first voltage integral value and the second voltage integral value;
[0112] The fundamental wave amplitude anomaly and harmonic anomaly module is configured to determine whether there is a fundamental wave amplitude anomaly and a harmonic anomaly in the CVT to be defect-recognized according to a preset fundamental wave amplitude range, a preset harmonic content threshold, and the secondary voltage waveform signal of the CVT to be defect-recognized;
[0113] The ungrounded low-voltage terminal defect determination module is configured to, when there is an internal defect, a crest distortion, no charge and discharge defect, a fundamental wave amplitude anomaly, and a harmonic anomaly in the CVT to be defect-recognized, determine that the CVT to be defect-recognized has an ungrounded low-voltage terminal defect, otherwise determine that the CVT to be defect-recognized does not have an ungrounded low-voltage terminal defect.
[0114] It should be noted that the embodiments of the device described above correspond to the above embodiments of the present invention and can implement the method for identifying the defect that the low-voltage terminal of the CVT is not grounded described in any of the above of the present invention. In addition, the embodiments of the above device are merely illustrative. The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the attached drawings of the device embodiments provided by the present invention, the connection relationship between modules indicates that they have a communication connection, which can be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art can understand and implement it without creative efforts.
[0115] Based on the above method embodiments of the present invention, a corresponding embodiment of an electronic device is provided.
[0116] An embodiment of the present invention provides an electronic device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the method for identifying the defect that the low-voltage terminal of the CVT is not grounded described in any one of the present invention, or when the processor executes the computer program, it implements the functions of each module in the above device embodiments.
[0117] Exemplarily, the computer program can be divided into one or more modules. The one or more modules are stored in the memory and executed by the processor to complete the present invention. The one or more modules can be a series of computer program instruction segments capable of completing specific functions, and these instruction segments are used to describe the execution process of the computer program in the terminal device.
[0118] The terminal device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The terminal device may include, but is not limited to, a processor and a memory.
[0119] The so-called processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The processor is the control center of the terminal device and connects various parts of the entire terminal device through various interfaces and lines.
[0120] The memory can be used to store the computer program and / or module. The processor realizes various functions of the terminal device by running or executing the computer program and / or module stored in the memory, and by calling the data stored in the memory. The memory mainly includes a program storage area and a data storage area. Among them, the program storage area can store an operating system, application programs required for at least one function, etc.; the data storage area can store data created according to the use of the mobile phone, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, at least one magnetic disk storage device, a flash memory device, or other volatile solid-state storage devices.
[0121] Based on the above method item embodiments, the present invention correspondingly provides storage medium item embodiments;
[0122] Another embodiment of the present invention provides a storage medium, which includes a stored computer program. When the computer program runs, it controls the device where the storage medium is located to execute any one of the above-mentioned CVT low-voltage terminal ungrounded defect identification methods of the present invention.
[0123] Among them, the above storage medium is a computer-readable storage medium, and the computer program includes computer program code, which can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.
[0124] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example" or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.
[0125] The above is the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.
Claims
1. A method for identifying a CVT low-voltage terminal ungrounded defect, characterized in that: include: Acquire the secondary voltage waveform signal of the CVT to be identified by defects and the secondary voltage waveform signal of the same-phase CVT; wherein the same-phase CVT is a CVT installed at a different position of the substation than the CVT to be identified by defects but belonging to the same phase; the same-phase CVT has no defects; In the case that the CVT to be identified has a voltage mutation, it is determined whether the CVT to be identified has an internal defect based on the secondary voltage waveform signal of the in-phase CVT; According to the secondary voltage waveform signal of the CVT to be identified by the defect, it is determined whether the CVT to be identified by the defect has peak distortion; According to the secondary voltage waveform signal of the CVT to be identified by the defect, a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation are calculated and generated, and whether the CVT to be identified by the defect has a charge and discharge defect is judged according to the first voltage integral value and the second voltage integral value; According to the preset fundamental wave amplitude range, the preset harmonic content threshold and the secondary voltage waveform signal of the CVT to be identified by the defect, it is judged whether the CVT to be identified by the defect has a fundamental wave amplitude abnormality and a harmonic abnormality; When the CVT to be identified has internal defects, peak distortion, no charging and discharging defects, abnormal fundamental amplitude and harmonic abnormalities, it is determined that the CVT to be identified has a low-voltage terminal ungrounding defect; otherwise, it is determined that the CVT to be identified does not have a low-voltage terminal ungrounding defect.
2. A method for identifying a CVT low-voltage terminal ungrounded defect as claimed in claim 1, characterized in that: Determine whether the CVT to be identified has a voltage mutation by the following methods: According to the preset time window, determine whether the voltage amplitude change of the secondary voltage waveform signal of the CVT to be identified within any time window exceeds the preset voltage mutation threshold. If so, it is determined that the CVT to be identified has a voltage mutation; if not, it is determined that the CVT to be identified has no voltage mutation.
3. A method for identifying a CVT low-voltage terminal ungrounded defect as claimed in claim 2, characterized in that: In the case that the CVT to be identified as defective has a voltage mutation, judging whether the CVT to be identified as defective has an internal defect according to the secondary voltage waveform signal of the CVT in phase, includes: According to the preset time window, determine whether the voltage amplitude change of the secondary voltage waveform signal of the same-phase CVT in any time window exceeds the preset voltage mutation threshold value. If so, determine that the same-phase CVT has a voltage mutation; if not, determine that the same-phase CVT does not have a voltage mutation; In the case of a voltage mutation in the same-phase CVT, it is determined that the CVT to be identified has no internal defects; When there is no voltage mutation in the same-phase CVT, it is determined that the CVT to be identified has an internal defect.
4. A method for identifying a CVT low-voltage terminal ungrounded defect as claimed in claim 3, characterized in that: The determining whether the CVT to be identified for defects has peak distortion according to the secondary voltage waveform signal of the CVT to be identified for defects includes: According to the secondary voltage waveform signal of the CVT to be identified by defects, the location of the voltage mutation and the target voltage amplitude of a preset number of sampling points before and after the zero crossing point are extracted; Determine whether the position of the voltage mutation of the CVT to be identified is only at the peak. If not, determine that there is no peak distortion in the CVT to be identified. If so, determine whether each target voltage amplitude is 0. When the target voltage amplitudes are all 0, it is determined that the CVT to be identified has no peak distortion; When the target voltage amplitude is not 0, it is determined that the CVT to be defect-identified has peak distortion.
5. A method for identifying a CVT low-voltage terminal ungrounded defect as claimed in claim 4, characterized in that: The method of calculating and generating a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation according to the secondary voltage waveform signal of the CVT to be identified by the defect, and judging whether the CVT to be identified by the defect has a charge and discharge defect according to the first voltage integral value and the second voltage integral value, comprises: According to the secondary voltage waveform signal of the CVT to be identified by the defect, a first voltage integral value within a preset period before the voltage mutation and a second voltage integral value within a preset period after the voltage mutation are calculated and generated; Calculate the absolute difference between the first voltage integral value and the second voltage integral value to generate an integral difference value; It is determined whether the integral difference exceeds a preset local distortion threshold value. If so, it is determined that the CVT to be identified has a charge and discharge defect. If not, it is determined that the CVT to be identified does not have a charge and discharge defect.
6. A method for identifying a CVT low-voltage terminal ungrounded defect as claimed in claim 5, characterized in that: The method of judging whether the CVT to be identified for defects has abnormal fundamental amplitude and abnormal harmonics according to a preset fundamental amplitude range, a preset harmonic content threshold, and a secondary voltage waveform signal of the CVT to be identified for defects includes: Perform Fourier transform on the secondary voltage waveform signal of the CVT to be identified, and obtain the spectrum information after Fourier transform; Extracting and generating fundamental wave amplitude and harmonic wave amplitude from the frequency spectrum information; Determine whether the fundamental wave amplitude of the CVT to be identified by defects is within a preset fundamental wave amplitude range. If so, determine that there is no fundamental wave amplitude abnormality in the CVT to be identified by defects. If not, determine that there is a fundamental wave amplitude abnormality in the CVT to be identified by defects. Calculate and generate the harmonic content of the CVT to be defect-identified according to the harmonic amplitude and the fundamental amplitude; Determine whether the harmonic content of the CVT to be identified as defective exceeds a preset harmonic content threshold. If so, determine that the CVT to be identified as defective has harmonic abnormality. If not, determine that the CVT to be identified as defective does not have harmonic abnormality.
7. A method for identifying a CVT low-voltage terminal ungrounded defect as claimed in claim 6, characterized in that: Also includes: When there is no voltage mutation in the CVT to be identified as defective, it is determined that there is no low-voltage terminal ungrounding defect in the CVT to be identified as defective.
8. A device for identifying a CVT low-voltage terminal ungrounded defect, characterized in that: include: Data acquisition module, internal defect judgment module, peak distortion judgment module, charge and discharge defect judgment module, fundamental wave amplitude abnormality and harmonic abnormality module and low voltage terminal ungrounded defect judgment module; The data acquisition module is used to acquire the secondary voltage waveform signal of the CVT to be identified by defects and the secondary voltage waveform signal of the same-phase CVT; wherein the same-phase CVT is a CVT installed at a different position of the substation than the CVT to be identified by defects but belonging to the same phase; the same-phase CVT has no defects; The internal defect determination module is used to determine whether the CVT to be identified has an internal defect based on the secondary voltage waveform signal of the same-phase CVT when there is a voltage mutation in the CVT to be identified; The peak distortion determination module is used to determine whether the CVT to be identified for defects has peak distortion according to the secondary voltage waveform signal of the CVT to be identified for defects; The charge and discharge defect determination module is used to calculate and generate a first voltage integral value before the voltage mutation and a second voltage integral value after the voltage mutation according to the secondary voltage waveform signal of the CVT to be identified as a defect, and determine whether the CVT to be identified as a defect has a charge and discharge defect according to the first voltage integral value and the second voltage integral value; The fundamental wave amplitude abnormality and harmonic abnormality module is used to determine whether the CVT to be identified for defects has fundamental wave amplitude abnormality and harmonic abnormality according to a preset fundamental wave amplitude interval, a preset harmonic content threshold and a secondary voltage waveform signal of the CVT to be identified for defects; The low-voltage terminal ungrounded defect judgment module is used to determine that the CVT to be defectively identified has a low-voltage terminal ungrounded defect when the CVT to be defectively identified has internal defects, peak distortion, no charging and discharging defects, fundamental wave amplitude abnormalities, and harmonic abnormalities; otherwise, it is determined that the CVT to be defectively identified does not have a low-voltage terminal ungrounded defect.
9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method for identifying the ungrounded defect of the CVT low-voltage terminal as described in any one of claims 1 to 7 can be implemented.
10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for identifying the ungrounded defect of the CVT low-voltage terminal as described in any one of claims 1 to 7 can be implemented.