A current transformer dielectric loss detection method, device, equipment and medium

Abstract

This invention belongs to the field of current transformer technology, specifically relating to a method, device, equipment, and dielectric for detecting dielectric loss in current transformers. Through dynamic trend analysis, by continuously monitoring and recording changes in dielectric loss over time, this invention can promptly identify abnormal growth patterns, provide early warnings of potential faults, and improve system operation and maintenance efficiency. Temperature and humidity correction steps are introduced to ensure that measurement results are not affected by external environmental fluctuations, improving the reliability and accuracy of the detection data. By combining the relationship between dielectric loss factor and voltage change, the equivalent dielectric constant is calculated and compared with standard values ​​or historical data, providing a quantitative assessment basis for the degree of dielectric aging. This helps to formulate more reasonable maintenance strategies. Through comprehensive analysis, it can not only determine the current operational safety of the transformer but also predict potential future risks, effectively extending the equipment's service life and ensuring the stability and safety of the power grid operation.

Description

Technical Field

[0001] This invention belongs to the field of current transformer technology, specifically relating to a method, apparatus, equipment, and medium for detecting dielectric loss in current transformers. Background Technology

[0002] Current transformers, as key components in power systems, are responsible for converting large currents on the high-voltage side into smaller currents on the low-voltage side, facilitating measurement and protection equipment monitoring the power grid's operational status. The performance of their internal insulation materials directly affects the transformer's reliability and service life. Dielectric loss, the energy loss caused by polarization hysteresis in the insulation material under an alternating electric field, is an important indicator of insulation performance. Over time and with changes in operating conditions, the insulation material may gradually age, leading to increased dielectric loss and consequently affecting the safety and stability of the current transformer.

[0003] Traditional methods for detecting dielectric loss often focus on measurements at a single moment, lacking the ability to track and analyze the evolution of dielectric loss over time. Furthermore, they often fail to adequately correct for environmental factors, potentially hindering the accurate assessment of long-term operational risks of instrument transformers. Especially in complex and variable real-world operating environments, fluctuations in temperature and humidity significantly impact dielectric loss; neglecting these factors can lead to misjudgments of the instrument transformer's health status.

[0004] The main problems faced by existing current transformer dielectric loss detection technologies include:

[0005] Lack of dynamic monitoring mechanism: Focusing only on real-time measurement results and ignoring the trend analysis of dielectric loss over time makes it difficult to detect potential insulation degradation problems in the early stage.

[0006] Insufficient correction for environmental factors: The direct impact of changes in ambient temperature and humidity on the measurement results was not adequately corrected, reducing the accuracy of the test results.

[0007] Inaccurate aging assessment: The lack of an effective method for calculating the equivalent dielectric constant makes it difficult to accurately quantify the aging degree of the medium, affecting the scientific nature of maintenance decisions. Summary of the Invention

[0008] The purpose of this invention is to provide a method, apparatus, equipment, and medium for detecting dielectric loss in current transformers. By integrating dynamic monitoring, environmental correction, and accurate assessment of aging, it significantly improves the scientific rigor and practicality of dielectric loss detection in current transformers, providing strong technical support for the safe operation and maintenance of power systems, and solving the problems in the prior art mentioned in the background.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a method for detecting dielectric loss in a current transformer, comprising the following steps:

[0010] a) Isolate the current transformer to be tested from the power system and ensure that it is in a non-operating state. Connect an AC voltage source to the primary side of the current transformer and set the voltage source to output an AC voltage with a preset frequency and amplitude.

[0011] b) Connect a high-impedance measuring device to the secondary side of the current transformer to detect the small current caused by dielectric loss.

[0012] c) Start the AC voltage source to make the current transformer run under the set AC voltage. Record the change of dielectric loss current in the first 5 minutes after the AC voltage is applied. Use a spectrum analyzer to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points.

[0013] d) Adjust the output voltage of the AC voltage source to another preset value, repeat step c), and obtain loss data at different voltage levels;

[0014] e) Based on the obtained loss factor and the trend of current change with voltage, calculate the equivalent dielectric constant of the medium, compare the calculated equivalent dielectric constant with the standard value or historical data, and assess the aging degree of the medium.

[0015] f) Analyze the trend of dielectric loss over time, identify any abnormal growth, and, in conjunction with ambient temperature and humidity conditions, correct the measurement results to determine the safe operating status of the current transformer.

[0016] 2. The method for detecting dielectric loss in a current transformer according to claim 1, characterized in that, in step a), connecting an AC voltage source to the primary side of the current transformer and setting the voltage source to output an AC voltage with a preset frequency and amplitude, includes:

[0017] Prepare the AC voltage source equipment, adjust its output frequency and amplitude to the preset value according to the testing requirements, and use a cable to connect the AC voltage source to the primary side interface of the current transformer.

[0018] The frequency of the output AC voltage is set on the AC voltage source according to the test standards of the current transformer or the actual operating conditions.

[0019] Gradually adjust the output voltage of the voltage source to the preset amplitude.

[0020] Preferably, a high-impedance measuring device is connected to the secondary side of the current transformer to detect minute currents caused by dielectric losses, including:

[0021] Ground the grounding terminal of the measuring device, and connect the input wire of the measuring device to the secondary side terminal of the current transformer;

[0022] The weak electrical signal is amplified by a high-impedance amplifier in the measuring device, and then the signal is processed.

[0023] The ADC digitizes the processed signal, converting it into a digital signal.

[0024] Preferably, in c), a spectrum analyzer is used to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points, including:

[0025] Start the AC voltage source and gradually increase the output of the AC voltage source until the preset voltage amplitude is reached;

[0026] Real-time monitoring and recording: Once the AC voltage stabilizes, the recording of dielectric loss current measured by the high-impedance measuring device on the secondary side of the current transformer will begin immediately.

[0027] After collecting and organizing the data, stop recording the data after 5 minutes, export the collected current data, perform spectrum analysis to generate a spectrum of the current signal, and identify and mark the key frequency points in the spectrum.

[0028] Loss factor calculation and evaluation: Based on the results of spectrum analysis, the loss factor at each key frequency point is calculated.

[0029] Preferably, in d), loss data at different voltage levels is obtained, including:

[0030] Before adjusting the voltage, record the current test data, including the loss factor, key frequency points, and corresponding current amplitude.

[0031] After safely shutting off the AC voltage source, reset the output voltage of the AC voltage source to the next preset value;

[0032] Repeated dielectric loss current recording and spectrum analysis: As described in step c), record the changes in dielectric loss current in the first 5 minutes after the AC voltage is applied, and use a spectrum analyzer to perform spectrum analysis to determine the key frequency points and loss factors at the new voltage level.

[0033] Preferably, in e), the calculated equivalent dielectric constant is compared with a standard value or historical data to assess the degree of aging of the dielectric, including:

[0034] Summarize all loss factors and corresponding current data obtained from tests at different voltage levels; for each voltage level, use the known loss factors and current amplitudes to estimate the loss angle of the dielectric and solve for the equivalent dielectric constant of the dielectric at different voltage levels.

[0035] Analyze the trend of the equivalent dielectric constant with voltage, and observe whether it increases monotonically, decreases or remains stable as the voltage increases;

[0036] The calculated equivalent dielectric constant is compared with the standard value or historical data of the current transformer under new conditions to obtain the comparison result. Based on the comparison result, the degree of aging of the dielectric is evaluated.

[0037] Preferably, in f), determining the safe operating status of the current transformer includes:

[0038] Monitor the dielectric loss factor, current, voltage, and capacitance of the current transformer, and record the ambient temperature and humidity during each measurement;

[0039] Establish a database to record the time, dielectric loss factor, ambient temperature and relative humidity parameters for each test. Use the collected data to plot the trend of dielectric loss factor over time and observe whether the dielectric loss factor shows a stable, increasing or decreasing trend.

[0040] Identify abnormal growth, set a threshold, and mark a potential abnormal growth point when the dielectric loss factor in a certain measurement exceeds this threshold;

[0041] The measurement results are corrected based on ambient temperature and humidity. The corrected value of the dielectric loss factor is compared with the uncorrected value to assess the importance of temperature and humidity correction.

[0042] The operating status of the current transformer is evaluated by combining the trend of dielectric loss factor over time, environmental correction results, and safety limits.

[0043] On the other hand, the present invention proposes a current transformer dielectric loss detection device, comprising:

[0044] The detection condition setting module is used to isolate the current transformer to be tested from the power system and ensure that it is in a non-operating state. It connects an AC voltage source to the primary side of the current transformer and sets the AC voltage output of the voltage source to a preset frequency and amplitude.

[0045] A micro-current detection module is used to connect a high-impedance measuring device to the secondary side of a current transformer to detect micro-currents caused by dielectric loss.

[0046] The spectrum analysis module is used to start the AC voltage source, so that the current transformer operates under the set AC voltage, record the change of dielectric loss current in the first 5 minutes after the AC voltage is applied, and use a spectrum analyzer to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points.

[0047] The repeat detection module is used to adjust the output voltage of the AC voltage source to another preset value and obtain loss data at different voltage levels.

[0048] The evaluation module is used to calculate the equivalent dielectric constant of the dielectric based on the obtained loss factor and the trend of current change with voltage, compare the calculated equivalent dielectric constant with the standard value or historical data, and evaluate the aging degree of the dielectric.

[0049] The status judgment module is used to analyze the trend of dielectric loss over time, identify whether there is abnormal growth, and correct the measurement results in combination with ambient temperature and humidity conditions to determine the safe operating status of the current transformer.

[0050] On the other hand, the present invention proposes a current transformer dielectric loss detection device, which includes a processor, a memory, and a dielectric loss detection program stored in the memory and executable by the processor. When the dielectric loss detection program is executed by the processor, it implements the steps of the current transformer dielectric loss detection method as described above.

[0051] On the other hand, the present invention proposes a computer-readable storage medium storing a dielectric loss detection program, wherein when the dielectric loss detection program is executed by a processor, it implements the steps of the current transformer dielectric loss detection method as described above.

[0052] Technical effects and advantages of the present invention: The method, apparatus, equipment and medium for detecting dielectric loss of current transformers proposed in this invention have the following advantages compared with the prior art:

[0053] This invention utilizes dynamic trend analysis: by continuously monitoring and recording the changes in dielectric loss over time, it can promptly identify abnormal growth patterns, provide early warnings of potential faults, and improve the system's operation and maintenance efficiency. It introduces temperature and humidity correction steps to ensure that measurement results are unaffected by external environmental fluctuations, thus improving the reliability and accuracy of the detection data. By combining the relationship between dielectric loss factor and voltage changes, it calculates the equivalent dielectric constant and compares it with standard values ​​or historical data, providing a quantitative assessment basis for the degree of dielectric aging. This helps in formulating more reasonable maintenance strategies. Through comprehensive analysis, it can not only determine the current operational safety of the instrument transformer but also predict potential future risks, effectively extending the equipment's service life and ensuring the stability and safety of the power grid operation. Attached Figure Description

[0054] Figure 1 This is a flowchart of a current transformer dielectric loss detection method according to the present invention;

[0055] Figure 2 This is a block diagram of a current transformer dielectric loss detection device according to the present invention;

[0056] Figure 3This is a block diagram of a current transformer dielectric loss detection device according to the present invention. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] This invention provides a method for detecting dielectric loss in current transformers. By integrating dynamic monitoring, environmental correction, and precise aging assessment, it significantly improves the scientific rigor and practicality of current transformer dielectric loss detection, providing strong technical support for the safe operation and maintenance of power systems. Details are as follows:

[0059] like Figure 1 As shown, Figure 1 This is a flowchart of a current transformer dielectric loss detection method according to the present invention.

[0060] In this embodiment, the above-mentioned method for detecting dielectric loss in a current transformer includes the following steps:

[0061] a) Isolate the current transformer to be tested from the power system and ensure that it is in a non-operating state. Connect an AC voltage source to the primary side of the current transformer and set the voltage source to output an AC voltage with a preset frequency and amplitude.

[0062] The specific steps for connecting an AC voltage source to the primary side of a current transformer and setting the output parameters are as follows:

[0063] Select a suitable AC voltage source: Based on the rated voltage of the current transformer and the test requirements, select an AC voltage source that can provide sufficient power and stable output. Ensure that the device has adjustable frequency and voltage output functions.

[0064] Prepare the connecting wires: Select high-quality insulated wires suitable for the current and voltage ratings. The length should be appropriate to avoid voltage drop due to excessive length or operational inconvenience due to excessive length. Check that the connecting terminals at both ends of the wire are clean and free of oxidation, and ensure that the contact surfaces are flat.

[0065] Disconnect the primary circuit: After ensuring that the current transformer is completely isolated from the power system, open the primary side junction box or connection point of the current transformer to prepare for connection to the AC voltage source.

[0066] Connecting to the AC voltage source: Securely connect one end of the prepared wire to the output port of the AC voltage source, and carefully connect the other end to the primary side terminal or winding terminal of the current transformer. During the connection process, follow the principle of "connecting the ground terminal first, then the power supply terminal" to reduce the generation of electrical sparks.

[0067] Set output parameters:

[0068] Frequency setting: On the control panel of the AC voltage source, set the frequency of the output AC voltage according to the test standards of the current transformer or the actual operating conditions. The general industrial standard is 50Hz or 60Hz, which can be adjusted by rotating the knob or by digital input.

[0069] Amplitude setting: According to the test plan, gradually adjust the output voltage of the voltage source to the preset amplitude. This process should be carried out slowly, while monitoring the voltmeter display to ensure that the output is stable and does not exceed the rated voltage of the current transformer.

[0070] Verification and Adjustment: Use a high-precision voltmeter and frequency meter to verify the actual output of the AC voltage source, ensuring that the frequency and voltage values ​​are consistent with the set values. If there is a deviation, fine-tune according to the measurement results until the expected set values ​​are achieved.

[0071] Before officially starting the test, double-check that all connections are secure and that safety measures are in place to ensure the entire test system is ready.

[0072] b) Connect a high-impedance measuring device to the secondary side of the current transformer to detect the small current caused by dielectric loss.

[0073] Furthermore, the specific steps for connecting a high-impedance measuring device to the secondary side of the current transformer are as follows:

[0074] Select a suitable high-impedance measuring device: Based on the specifications of the current transformer and the test requirements, select a measuring device with high sensitivity and high impedance (usually greater than 1MΩ) to ensure that it can accurately capture the small current signal generated by dielectric loss.

[0075] Prepare the measuring leads: Select low-noise, high-insulation-strength shielded wires as connecting leads to reduce the impact of external interference on the measurement results. Ensure that the connectors at both ends of the leads are compatible with the interfaces of the measuring device and the current transformer.

[0076] Disconnect secondary load: Before making any connections, ensure that there are no loads connected to the secondary side of the current transformer to avoid measurement errors and safety hazards.

[0077] Connecting the High Impedance Measuring Device: First, properly ground the measuring device's grounding terminal to eliminate electrostatic interference. Then, carefully connect the measuring device's input leads to the secondary side terminals of the current transformer, following the correct polarity connection (if the measuring device has polarity requirements). Ensure the connection is secure, but avoid overtightening to the point of damaging the terminals or leads. Calibration and Warm-up: Turn on the high impedance measuring device and perform the necessary calibration operations according to the operation manual, including zero-point adjustment and range setting. Allow the measuring device to warm up for a period of time, typically according to the time recommended in the equipment manual, to ensure measurement accuracy.

[0078] Pre-test checks: Before officially starting the AC voltage source, double-check all connections to ensure they are correct and that the measuring device is functioning normally without any abnormal alarms or indications. Ensure the test area is safe and unobstructed, and prepare to record measurement data. These steps ensure the high-impedance measuring device is correctly and safely connected to the secondary side of the current transformer, preparing for subsequent dielectric loss testing.

[0079] The specific structural components and working principle of the high-impedance measuring device are summarized below:

[0080] Core Component: High-Impedance Amplifier: This is the core component of the measuring device, designed to amplify weak electrical signals. It features extremely high input impedance (typically greater than 100MΩ), ensuring that no additional load is placed on the small current on the secondary side of the current transformer during the measurement process, thus guaranteeing measurement accuracy.

[0081] Filtering and damping circuits: In order to reduce external electromagnetic interference and internal circuit oscillations, the device usually includes a low-pass filter and a damping resistor to filter out high-frequency noise and stabilize the circuit response, making the measurement results purer and more stable.

[0082] Preamplifier stage: First, the small current signal is initially amplified. This stage is usually designed with high gain and low noise characteristics to ensure the effective extraction of weak signals.

[0083] Gain adjustment and range switching: To adapt to different measurement needs, the device is usually equipped with adjustable gain control and range selection switch, allowing users to adjust the amplification factor according to the expected signal size, thereby optimizing the measurement range and resolution.

[0084] Analog-to-digital converter (ADC): The pre-amplified signal is fed into the ADC for digitization, converting it into a digital signal for subsequent analysis and display. The ADC's resolution and sampling rate directly affect the accuracy and real-time performance of the measurement results.

[0085] Data Analysis and Display Unit: The final digital signal is sent to the processor or microcontroller, where it is processed by built-in algorithms to calculate parameters related to dielectric loss, such as the dielectric loss factor (tanδ). The processing results are displayed on the screen or output to a computer via a communication interface for further analysis.

[0086] In summary, the high-impedance measurement device, through precise electronic design, enables accurate capture and analysis of minute currents on the secondary side of current transformers, providing crucial data support for evaluating the insulation performance of current transformers.

[0087] c) Start the AC voltage source to make the current transformer run under the set AC voltage. Record the change of dielectric loss current in the first 5 minutes after the AC voltage is applied. Use a spectrum analyzer to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points.

[0088] The specific steps for starting the AC voltage source and performing spectrum analysis of the dielectric loss current are as follows:

[0089] Pre-start safety checks: Before turning on the AC voltage source, double-check the isolation status of the current transformer, ensure all connections are correct, and confirm that the measuring equipment is ready. Ensure all personnel are away from high-voltage areas and notify relevant personnel that testing is about to begin.

[0090] Start the AC voltage source: According to the established test plan, gradually increase the output of the AC voltage source until the preset voltage amplitude is reached. This process should be slow and smooth, while monitoring the voltmeter reading to ensure stable output.

[0091] Real-time monitoring and recording: Once the AC voltage stabilizes, immediately begin recording the dielectric loss current on the secondary side of the current transformer as measured by the high-impedance measuring device. Use a data acquisition system or set it directly on the measuring device to record the current changes within the first 5 minutes after the AC voltage is applied. Ensure the recording intervals are short enough to capture any instantaneous changes.

[0092] Data collection and processing: After 5 minutes, stop data recording and export the collected current data to a computer or other analysis tools to prepare for subsequent analysis.

[0093] Spectrum analysis: Use professional spectrum analysis software or hardware spectrum analyzer to import the recorded dielectric loss current data.

[0094] Choose an appropriate analysis window and resolution bandwidth to reduce leakage effects and improve analysis accuracy. Perform a Fast Fourier Transform (FFT) or other applicable spectrum analysis algorithm to generate a spectrum of the current signal. Identify and mark the key frequency points in the spectrum; these are usually the frequencies where dielectric loss is most significant, corresponding to specific vibration modes or defect responses within the dielectric.

[0095] Loss Factor Calculation and Assessment: Based on the results of spectrum analysis, calculate the loss factor (tanδ) at each key frequency point, which is the ratio of dielectric power loss to energy storage power. Compare these loss factors with standard values ​​or historical data to assess the health status of the current transformer's insulation material. If an abnormally high loss factor is found, further analysis of the cause should be conducted, and maintenance measures should be considered.

[0096] The above steps can effectively evaluate the dielectric loss characteristics of a current transformer when it operates under a set AC voltage, providing a scientific basis for the diagnosis of insulation performance.

[0097] The following is a detailed procedure for performing spectral analysis on the recorded dielectric loss current using a spectrum analyzer:

[0098] Data preparation: Ensure that the dielectric loss current data collected from the current transformer has been completely and accurately transmitted to the spectrum analyzer or connected computer. This typically involves importing the data file into the spectrum analysis software via USB, Ethernet, or a dedicated interface.

[0099] Software Setup: Open the spectrum analysis software, select "New Project" or "Workspace," and import the current time series data file obtained from the current transformer. Set the sampling rate and time range, ensuring they match the settings used during the original data acquisition to maintain data accuracy.

[0100] Preprocessing adjustments: Apply appropriate filters to remove high-frequency noise and low-frequency trends, such as using high-pass and low-pass filters, to ensure the analysis is focused on the frequency range of interest. Consider baseline correction to remove any DC bias or background noise for clearer observation of dielectric loss characteristics.

[0101] Perform spectrum analysis: Select the Fast Fourier Transform (FFT) as the analysis method, which is the standard technique for analyzing the spectrum of periodic signals. Set the spectral resolution and select an appropriate frequency resolution bandwidth (FRB) based on the frequency details required for analysis. Perform the FFT transform to generate a spectrum of the current signal, showing the amplitude distribution at different frequencies.

[0102] Identifying key frequency points: Examine the spectrum and note those frequency points exhibiting significant peaks, as these are often the main contributors to dielectric loss. Record the location of these key frequency points and their corresponding amplitude values; these points may indicate specific failure modes or defects in the insulation material.

[0103] The specific steps for calculating the loss factor (tanδ) at each key frequency point based on the spectral analysis results are as follows:

[0104] Data extraction: Identify and record the amplitude of all key frequency points from the spectrum analysis results. Key frequency points are typically those frequencies that exhibit abnormally high dielectric losses (manifested as peaks on the spectrum).

[0105] Reactive power amplitude determination: Determine a reference frequency point representing a lossless (or near-lossless) state, typically far from any significant loss peaks. Record the current amplitude at this frequency; this will be used to calculate the relative amount of energy storage power. Ensure the selected reference point reflects the ideal or baseline behavior of the equipment.

[0106] Calculating the energy storage power amplitude: Assuming the current amplitude at the reference frequency represents the energy storage component (lossless current), calculate the energy storage power amplitude. Although actual calculations of energy storage power require more complex formulas, in this simplified model, the energy storage power can be approximated as the square of the amplitude at the reference frequency multiplied by a constant factor (depending on the specific parameters of the system, such as inductance and capacitance).

[0107] Calculating the dielectric loss power amplitude: For each critical frequency point, the corresponding dielectric loss power amplitude can be estimated by multiplying the difference between the square of the current amplitude at that frequency point and the square of the current amplitude at the reference frequency point by the same constant factor. This is because the loss power reflects the lossy current component.

[0108] Calculate the loss factor (tanδ): Calculate the loss factor (tanδ) at each critical frequency point using the following formula: [\tan\de l ta=\frac{\text{dielectric loss power amplitude}}{\text{energy storage power amplitude}}=\frac{I_{\text{l oss}}^2}{I_{\text{ref}}^2}\t imes\text{constant factor}] where l oss is the current amplitude at the critical frequency point, ref is the current amplitude at the reference frequency point, and the constant factor needs to be determined according to the actual situation.

[0109] Assessment and Interpretation: Analyze the calculated loss factor values, compare them at different frequency points or with standard thresholds and historical data to assess the health of the dielectric. A higher tanδ value indicates greater dielectric loss at the corresponding frequency, which may be a sign of deteriorated insulation performance, requiring further investigation into the cause, such as partial discharge, aging, or contamination. Prepare an assessment report, summarizing the loss factor at each key frequency point, identifying potential problem areas, and proposing maintenance or monitoring recommendations.

[0110] By following the steps above, we can not only quantify the degree of dielectric loss, but also pinpoint the frequency of problems, providing a scientific basis for maintenance decisions of power equipment.

[0111] d) Adjust the output voltage of the AC voltage source to another preset value, repeat step c), and obtain loss data at different voltage levels;

[0112] Furthermore, the specific steps for adjusting the AC voltage source output and repeating step c) to obtain loss data at different voltage levels are as follows:

[0113] Record current test data: Before adjusting the voltage, ensure that all test data at the current voltage level has been recorded in detail, including loss factor, key frequency points, and corresponding current amplitude, for subsequent analysis and comparison.

[0114] Safely shut off the AC voltage source: Following the equipment operating procedures, safely reduce and shut off the current AC voltage output, ensuring the current transformer returns to a non-test state. At this point, the AC voltage source can be appropriately disconnected from the current transformer to facilitate further voltage adjustment.

[0115] Adjust the AC voltage source settings: According to the test plan, reset the output voltage of the AC voltage source to the next preset value. This new voltage should be higher or lower than the previous test value to explore the effect of different voltage levels on dielectric loss characteristics. During adjustment, care should be taken to avoid exceeding the rated voltage range of the current transformer to ensure test safety.

[0116] Restart the AC voltage source: After verifying that all connections are correct, gradually start the AC voltage source, following the previous operating procedure, slowly increasing the voltage to the new preset value, and ensuring stable output.

[0117] Repeated dielectric loss current recording and spectrum analysis: Following step c), record the changes in dielectric loss current again within the first 5 minutes after the AC voltage is applied, and perform spectrum analysis using a spectrum analyzer to determine the key frequency points and loss factor at the new voltage level. Ensure that the test conditions and analysis parameters are consistent with the previous step to facilitate data comparison.

[0118] Data processing and comparison: Compare the test results at the new voltage level with the test data at the previous voltage level to analyze the trend of dielectric loss as voltage changes. Pay special attention to the increase or decrease of the loss factor and whether there are changes at key frequency points. This helps to understand the impact of voltage on insulation performance and evaluate the stability of the current transformer under different operating conditions.

[0119] Recording and Archiving: Record all data and observations from this test in detail, including the voltage adjustment process, test parameters, and analytical conclusions, to form a complete test report. Ensure all data is accurately preserved for future research, verification, or long-term tracking.

[0120] By following the steps above, the dielectric loss characteristics of current transformers at different voltage levels can be systematically evaluated, providing comprehensive data support for a deeper understanding of their insulation performance.

[0121] e) Based on the obtained loss factor and the trend of current change with voltage, calculate the equivalent dielectric constant of the medium, compare the calculated equivalent dielectric constant with the standard value or historical data, and assess the aging degree of the medium.

[0122] The specific steps for assessing the aging degree of a dielectric material are as follows: The equivalent dielectric constant of the dielectric is calculated based on the loss factor and the current-voltage variation trend.

[0123] Data processing: Summarize all loss factors (tanδ) and corresponding current data obtained from tests at different voltage levels. Ensure the accuracy and completeness of the data to prepare for subsequent calculations.

[0124] Calculate the dielectric loss angle: For each voltage level, using the known loss factor (tanδ) and current amplitude, the dielectric loss angle (δ) is initially calculated through theoretical models or experimental formulas. This is a direct reflection of dielectric loss.

[0125] Apply a dielectric constant model: Use an appropriate theoretical model (such as the Debye model, the Colle-Colle model, or a simplified model) to correlate the loss factor, current (or capacitance), and dielectric constant (ε). These models typically include the real part (ε') and the imaginary part (ε”) of the dielectric constant, the latter of which is related to the loss.

[0126] Calculating the equivalent dielectric constant: Based on the above model and experimental data, the equivalent dielectric constant of the dielectric at different voltage levels is calculated. The equivalent dielectric constant may be a complex function involving multiple variables such as loss factor, frequency, and voltage, and the calculation needs to be performed according to the specific model and experimental conditions.

[0127] Trend analysis: This involves analyzing the trend of the equivalent dielectric constant as a function of voltage, observing whether it monotonically increases, decreases, or remains stable with increasing voltage. This trend helps in understanding how dielectric properties change with electric field strength and is one of the key indicators for evaluating aging characteristics.

[0128] Comparison and assessment of aging: Compare the calculated equivalent dielectric constant value with standard values ​​or historical data of this type of current transformer under new conditions. Significant deviations from standard or historical data may indicate dielectric aging or performance degradation. Analyze the rate of change of the equivalent dielectric constant or the slope of the loss factor with voltage; increases in these parameters generally indicate increased dielectric losses and accelerated aging.

[0129] Based on the comparison results, the aging degree of the medium is comprehensively assessed, classified into levels (such as light, moderate, and severe aging), and corresponding maintenance or replacement recommendations are proposed.

[0130] Report Formulation: Compile all calculations, analysis results, and assessment conclusions into a written report, including graphs showing changes in the equivalent dielectric constant, comparative analysis with standard or historical data, and a detailed assessment of the degree of aging. The report should provide a clear basis for subsequent decision-making.

[0131] These steps allow for a systematic assessment of the dielectric properties and aging degree of current transformer media, providing important maintenance guidance for the safe operation of power systems.

[0132] The specific steps for calculating the dielectric loss angle (δ) are as follows. Here, we directly use the known loss factor (tanδ) for calculation, because the loss factor is defined as the tangent of the dielectric loss angle:

[0133] Data collection: Ensure you have accurately measured and recorded the dielectric loss factor (tanδ) at different voltage levels. The loss factor is the ratio of dielectric power loss to energy storage power, and in practice, it is usually obtained indirectly through methods such as spectrum analysis.

[0134] Understanding the concept: Review and confirm the relationship between the loss factor (tanδ) and the dielectric loss angle (δ). Mathematically, [\tanδ=\frac{\si nδ}{\cosδ}=\tan(δ)], therefore, the loss angle δ can be directly obtained through the arctangent function of the loss factor (arctan or tan^-1).

[0135] Calculate the loss angle: For each voltage level, use the arctangent function of a calculator or mathematical software to calculate the loss angle (δ) in degrees. Most modern calculation tools offer both degrees and radians; ensure that degrees are selected as the appropriate unit for your engineering application. Record the loss angle (δ) value for each voltage level.

[0136] Unit conversion: If the calculation result is given in radians, but engineering practice uses degrees, remember to convert the unit. 1 radian is approximately equal to 57.3 degrees, that is, [δ_{\text{degree}}=δ_{\text{radian}}\t imes\frac{180}{\pi}].

[0137] Data organization: Organize all calculated loss angle (δ) values ​​into tables or graphs according to voltage levels for easy and intuitive analysis. The trend of loss angle changes with voltage may reflect changes in dielectric properties, such as aging or contamination levels.

[0138] Analysis and Interpretation: The impact of the dielectric loss angle (δ) on dielectric properties is analyzed. Generally, a larger loss angle indicates higher dielectric loss, potentially indicating a decline in the quality or aging of the insulating material. Comparing the loss angles at different voltage levels assesses the variation of dielectric properties with electric field strength, providing a basis for subsequent maintenance and fault diagnosis.

[0139] Through the above steps, the dielectric loss angle (δ) can be directly calculated from the known loss factor (tanδ), thereby enabling in-depth analysis and understanding of the dielectric properties and their changing trends of the current transformer insulation material.

[0140] The specific steps for applying a dielectric constant model to correlate loss factor, current (or capacitance), and dielectric constant (ε) are as follows. Here, the commonly used Colle-Colle model is used as an example because it can well describe the complex dielectric properties of many practical materials:

[0141] Data preparation: Ensure that current (or more accurately, capacitance) data at different frequencies or voltages, along with the corresponding loss factors (tanδ), have been collected. Organize this data to prepare for model fitting.

[0142] Model Selection: The Colle-Colle model was chosen because it considers not only the real part (ε') of the dielectric constant but also the imaginary part (ε”) related to losses, making it suitable for describing media with multiple relaxation mechanisms.

[0143] Understanding the Colle-Colle model:

[0144] ε*(ω)=ε′(ω)-jε″(ω)=ε ∞ +Δε / 1+(jωτ) 1-α

[0145] Where ε*(ω) is the complex permittivity, ε′ is the real part of the permittivity, and ε″ is the imaginary part of the permittivity. ∞ It is the dielectric constant in the high-frequency limit, Δε=εs -ε ∞ ω is the relaxation strength of the dielectric constant, ω is the angular frequency, τ is the relaxation time, and α is the dispersion index (usually between 0 and 1).

[0146] Parameter estimation: Based on existing experimental data, preliminary estimation of model parameters is performed. This may require using numerical methods (such as least squares) to fit the experimental data to the model equations and find the optimal parameter combination (Δε, τ, α). Parameter optimization is then performed using software tools (such as MATLAB, Python, etc.) through iterative calculations to minimize the error between the model predictions and the measured data.

[0147] Model Validation: Using the optimized parameters, the Colle-Colle model was applied to all data to calculate the real and imaginary parts of the dielectric constant at each frequency or voltage. The curves of the real part (ε′) and imaginary part (ε″) as a function of frequency or voltage were plotted and compared with experimental data to verify the applicability and accuracy of the model.

[0148] Analysis and Application: Analyze the trend of dielectric constant (especially ε″) with frequency or voltage to evaluate the loss characteristics of the dielectric. Compare the calculated dielectric constant with standard values ​​or historical data to assess the aging of the dielectric. Based on the model results, propose specific recommendations for improving or maintaining the dielectric performance.

[0149] Through the above steps, the Colle-Colle model can be effectively applied to correlate loss factor, current (or capacitance) and dielectric constant, providing strong theoretical support for a deeper understanding of the dielectric properties and aging state of materials.

[0150] f) Analyze the trend of dielectric loss over time, identify any abnormal growth, and, in conjunction with ambient temperature and humidity conditions, correct the measurement results to determine the safe operating status of the current transformer.

[0151] The specific steps for analyzing the trend of dielectric loss over time and combining the measurement results with environmental factors to determine the safe operating status of the current transformer are as follows:

[0152] 1. Data collection and organization

[0153] Long-term monitoring: Record the dielectric loss factor (tanδ), current, voltage and capacitance of the current transformer regularly (e.g., monthly or quarterly), and record the ambient temperature and humidity at the time of each measurement.

[0154] Data processing: Establish a database to record key parameters such as the time of each test, dielectric loss factor, ambient temperature (T), and relative humidity (RH).

[0155] 2. Trend Analysis

[0156] Plot a trend graph: Using the collected data, plot a trend graph of the dielectric loss factor (tanδ) over time. Observe whether tanδ shows a stable, increasing, or decreasing trend.

[0157] Identify abnormal growth: Set a threshold (such as the average value of historical data plus a certain standard deviation). When the tanδ of a certain measurement exceeds this threshold, it is marked as a potential abnormal growth point, and the cause needs to be further analyzed.

[0158] 3. Environmental correction

[0159] Temperature effect correction: The dielectric loss factor typically increases with increasing temperature. The measured tanδ is corrected for temperature using known temperature dependence formulas (such as the Arrhenius equation) or correction factors provided by the equipment manufacturer.

[0160] Humidity effect correction: In high humidity environments, moisture intrusion increases media loss. Based on equipment characteristics and published research findings, the influence of humidity on tanδ is determined, and corresponding corrections are made.

[0161] 4. Make a comprehensive judgment based on environmental factors.

[0162] Comprehensive analysis of environmental factors: Compare the corrected tanδ value with the uncorrected value to assess the importance of temperature and humidity corrections. Analyze whether the trend of tanδ has changed after correction, and whether this change indicates potential problems.

[0163] 5. Safety Status Assessment

[0164] Safety standard comparison: Refer to the safety limits for dielectric loss of current transformers in industry standards (such as IEC standards) to determine whether the corrected tanδ is still within the safe range.

[0165] Comprehensive assessment: The operating status of the current transformer is evaluated by combining the trend of tanδ over time, environmental correction results, and safety limits. If tanδ continues to increase and exceeds the safety limit, it indicates potential insulation aging or other fault risks, requiring timely measures such as enhanced monitoring, preventative maintenance, or replacement.

[0166] 6. Reports and Recommendations

[0167] Write an analysis report: Summarize the analysis process, correction methods, problems found and conclusions, and propose specific maintenance suggestions or preventive measures.

[0168] Feedback and Action: Submit the report to the relevant departments and arrange necessary maintenance work based on the recommendations to ensure the long-term safe operation of the current transformer.

[0169] By following the steps above, we can systematically analyze the changing trend of dielectric loss of current transformers over time, make reasonable corrections in conjunction with environmental factors, and thus accurately determine their safe operating status and take corresponding management measures.

[0170] On the other hand, the present invention proposes a current transformer dielectric loss detection device, such as... Figure 2 As shown, it includes: a detection condition setting module, a micro current detection module, a spectrum analysis module, a repeat detection module, an evaluation module, and a status judgment module.

[0171] Specifically, the detection condition setting module is used to isolate the current transformer to be tested from the power system and ensure that it is in a non-operating state, connect an AC voltage source to the primary side of the current transformer, and set the voltage source to output an AC voltage with a preset frequency and amplitude.

[0172] Specifically, the micro-current detection module is used to connect a high-impedance measuring device to the secondary side of the current transformer to detect the micro-current caused by dielectric loss.

[0173] Specifically, the spectrum analysis module is used to start the AC voltage source, enabling the current transformer to operate under the set AC voltage, record the change in dielectric loss current within the first 5 minutes after the AC voltage is applied, and use a spectrum analyzer to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points.

[0174] Specifically, the repetitive detection module is used to adjust the output voltage of the AC voltage source to another preset value and obtain loss data at different voltage levels;

[0175] Specifically, the evaluation module is used to calculate the equivalent dielectric constant of the dielectric based on the obtained loss factor and the trend of current changing with voltage, compare the calculated equivalent dielectric constant with the standard value or historical data, and evaluate the degree of aging of the dielectric.

[0176] Specifically, the status judgment module is used to analyze the trend of dielectric loss over time, identify whether there is abnormal growth, and, in combination with ambient temperature and humidity conditions, correct the measurement results to determine the safe operating status of the current transformer.

[0177] In addition, the aforementioned detection condition setting module, micro current detection module, spectrum analysis module, repeated detection module, evaluation module, and state judgment module are also used to implement other steps of the aforementioned current transformer dielectric loss detection method, which will not be elaborated here.

[0178] In addition, such as Figure 3As shown, the present invention also provides a terminal device. The current transformer dielectric loss detection method involved in this embodiment is mainly applied in the terminal device, which can be a PC, portable computer, mobile terminal or other device with display and processing functions.

[0179] Specifically, the terminal device may include a processor (e.g., CPU), a communication bus, a user interface, a network interface, and memory. The communication bus is used to enable communication between these components; the user interface may include a display screen or an input unit such as a keyboard; the network interface may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface); the memory may be high-speed RAM or non-volatile memory, such as disk storage, and may also optionally be a storage device independent of the aforementioned processor.

[0180] The memory stores a readable storage medium, which in turn stores a dielectric loss detection program. The processor can call the dielectric loss detection program stored in the memory and execute the current transformer dielectric loss detection method provided in this embodiment of the invention.

[0181] Understandably, a readable storage medium can be a tangible device capable of holding and storing instructions for use by an instruction execution device. A computer-readable storage medium can be, for example—but not limited to—an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination thereof. The computer-readable storage medium as used herein is not to be construed as a transient signal itself, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0182] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0183] Computer program instructions used to perform operations according to this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smallalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuits, such as programmable logic circuits, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), are personalized by utilizing state information from computer-readable program instructions. These electronic circuits can execute computer-readable program instructions to implement various aspects of this disclosure.

[0184] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of detecting dielectric loss in a current transformer, characterized by, Includes the following steps: a) Isolate the current transformer to be tested from the power system and ensure that it is in a non-operating state. Connect an AC voltage source to the primary side of the current transformer and set the voltage source to output an AC voltage with a preset frequency and amplitude. b) Connect a high-impedance measuring device to the secondary side of the current transformer to detect the small current caused by dielectric loss. c) Start the AC voltage source to make the current transformer run under the set AC voltage. Record the change of dielectric loss current in the first 5 minutes after the AC voltage is applied. Use a spectrum analyzer to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points. d) Adjust the output voltage of the AC voltage source to another preset value, repeat step c), and obtain loss data at different voltage levels; e) Based on the obtained loss factor and the trend of current variation with voltage, calculate the equivalent dielectric constant of the dielectric, compare the calculated equivalent dielectric constant with the standard value or historical data, and assess the aging degree of the dielectric, including: Summarize all loss factors and corresponding current data obtained from tests at different voltage levels; for each voltage level, use the known loss factors and current amplitudes to estimate the loss angle of the dielectric and solve for the equivalent dielectric constant of the dielectric at different voltage levels. Analyze the trend of the equivalent dielectric constant with voltage, and observe whether it increases monotonically, decreases or remains stable as the voltage increases; The calculated equivalent dielectric constant value is compared with the standard value or historical data under the new condition of the current transformer to obtain the comparison result. Based on the comparison result, the degree of aging of the dielectric is evaluated. f) Analyze the trend of dielectric loss over time, identify any abnormal increases, and, in conjunction with ambient temperature and humidity conditions, correct the measurement results to determine the safe operating status of the current transformer, including: Monitor the dielectric loss factor, current, voltage, and capacitance of the current transformer, and record the ambient temperature and humidity during each measurement; Establish a database to record the time, dielectric loss factor, ambient temperature and relative humidity parameters for each test. Use the collected data to plot the trend of dielectric loss factor over time and observe whether the dielectric loss factor shows a stable, increasing or decreasing trend. Identify abnormal growth, set a threshold, and mark a potential abnormal growth point when the dielectric loss factor in a certain measurement exceeds this threshold; The measurement results are corrected based on ambient temperature and humidity. The corrected value of the dielectric loss factor is compared with the uncorrected value to assess the importance of temperature and humidity correction. The operating status of the current transformer is evaluated by combining the trend of dielectric loss factor over time, environmental correction results, and safety limits.

2. The method of claim 1, wherein, In step a), connecting an AC voltage source to the primary side of a current transformer and setting the voltage source to output an AC voltage with a preset frequency and amplitude includes: Prepare the AC voltage source equipment, adjust its output frequency and amplitude to the preset value according to the testing requirements, and use a cable to connect the AC voltage source to the primary side interface of the current transformer. The frequency of the output AC voltage is set on the AC voltage source according to the test standards of the current transformer or the actual operating conditions. Gradually adjust the output voltage of the voltage source to the preset amplitude.

3. The method of claim 2, wherein, In b), a high-impedance measuring device is connected to the secondary side of the current transformer to detect the minute current caused by dielectric loss, including: Ground the grounding terminal of the measuring device, and connect the input wire of the measuring device to the secondary side terminal of the current transformer; The weak electrical signal is amplified by a high-impedance amplifier in the measuring device, and then the signal is processed. The ADC digitizes the processed signal, converting it into a digital signal.

4. The method of claim 3, wherein, In c), a spectrum analyzer is used to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points, including: Start the AC voltage source and gradually increase the output of the AC voltage source until the preset voltage amplitude is reached; Real-time monitoring and recording: Once the AC voltage stabilizes, the recording of dielectric loss current measured by the high-impedance measuring device on the secondary side of the current transformer will begin immediately. After collecting and organizing the data, stop recording the data after 5 minutes, export the collected current data, perform spectrum analysis to generate a spectrum of the current signal, and identify and mark the key frequency points in the spectrum. Loss factor calculation and evaluation: Based on the results of spectrum analysis, the loss factor at each key frequency point is calculated.

5. The method of claim 4, wherein, In d), loss data at different voltage levels is obtained, including: Before adjusting the voltage, record the current test data, including the loss factor, key frequency points, and corresponding current amplitude. After safely shutting off the AC voltage source, reset the output voltage of the AC voltage source to the next preset value; Repeated dielectric loss current recording and spectrum analysis: As described in step c), record the changes in dielectric loss current in the first 5 minutes after the AC voltage is applied, and use a spectrum analyzer to perform spectrum analysis to determine the key frequency points and loss factors at the new voltage level.

6. A current transformer dielectric loss detection device, employing the current transformer dielectric loss detection method according to any one of claims 1-5, characterized in that, include: The detection condition setting module is used to isolate the current transformer to be tested from the power system and ensure that it is in a non-operating state. It connects an AC voltage source to the primary side of the current transformer and sets the AC voltage output of the voltage source to a preset frequency and amplitude. A micro-current detection module is used to connect a high-impedance measuring device to the secondary side of a current transformer to detect micro-currents caused by dielectric loss. The spectrum analysis module is used to start the AC voltage source, so that the current transformer operates under the set AC voltage, record the change of dielectric loss current in the first 5 minutes after the AC voltage is applied, and use a spectrum analyzer to perform spectrum analysis on the recorded dielectric loss current to determine the loss factor at key frequency points. The repeat detection module is used to adjust the output voltage of the AC voltage source to another preset value and obtain loss data at different voltage levels. The evaluation module is used to calculate the equivalent dielectric constant of the dielectric based on the obtained loss factor and the trend of current change with voltage, compare the calculated equivalent dielectric constant with the standard value or historical data, and evaluate the aging degree of the dielectric. The status judgment module is used to analyze the trend of dielectric loss over time, identify whether there is abnormal growth, and correct the measurement results in combination with ambient temperature and humidity conditions to determine the safe operating status of the current transformer.

7. A current transformer dielectric loss detection apparatus characterized by, The current transformer dielectric loss detection device includes a processor, a memory, and a dielectric loss detection program stored in the memory and executable by the processor, wherein when the dielectric loss detection program is executed by the processor, it implements the steps of the current transformer dielectric loss detection method as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a dielectric loss detection program, wherein when the dielectric loss detection program is executed by a processor, it implements the steps of the current transformer dielectric loss detection method as described in any one of claims 1 to 5.

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