Voltage transformer field calibration system and state diagnosis method

Abstract

The invention discloses a voltage transformer field calibration system and a state diagnosis method, and relates to the technical field of power equipment detection, and the method comprises the following steps: measuring the primary voltage and secondary voltage of a standard voltage transformer, and calculating the transformation ratio of the voltage transformer and the phase difference of the standard voltage transformer; obtaining the secondary voltage of the voltage transformer, and combining the primary voltage of the voltage transformer to obtain the phase difference of the voltage transformer; calculating a voltage error rate according to the secondary voltage of the standard voltage transformer and the secondary voltage of the voltage transformer, constructing a comprehensive calibration index model, and obtaining a field calibration coefficient of the voltage transformer; and acquiring working state data of the voltage transformer, constructing a state diagnosis model by adopting a support vector machine algorithm in combination with the field calibration coefficient of the voltage transformer to obtain a state diagnosis coefficient, performing comparative analysis on the state diagnosis coefficient and a state diagnosis threshold value, and diagnosing whether the state of the voltage sensor is abnormal or not. The method further improves the verification precision, and solves a problem that a conventional measurement and calculation method is large in error.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment detection, and more specifically, to a on-site calibration system and a state diagnosis method for a voltage transformer. Background Art

[0002] Voltage transformers are widely used in power systems for voltage measurement and monitoring, and their accuracy is crucial for the stability of power systems. As the service time of power equipment increases, voltage transformers may experience performance degradation or failures. Therefore, regular on-site calibration and state diagnosis become particularly important. However, traditional voltage transformer calibration methods are mostly manual inspections, which are inefficient and easily affected by human factors, and lack real-time monitoring and diagnosis of equipment status. Voltage transformers are mainly used to transform voltages proportionally and play a crucial role in power systems. They can convert high voltages into low voltages proportionally for voltage measurement by various measuring instruments and protection actions of relay protection devices.

[0003] In the prior art, traditional voltage transformer calibration methods have many deficiencies. On the one hand, most calibrations rely only on the comparison of single voltage parameters and cannot comprehensively reflect the true performance of voltage transformers, resulting in poor accuracy of calibration results. For example, only focusing on the secondary voltage value and ignoring important parameters such as phase difference may cause voltage transformers with phase deviation problems to not be detected in time. On the other hand, the hardware of on-site calibration systems lacks adaptability. In a complex electromagnetic environment, the signal acquisition module cannot effectively cope with interference, and the conventional fixed sampling frequency cannot specifically avoid or capture interference frequency bands, seriously affecting the accuracy of calibration data. At the same time, due to the large differences in on-site power supply situations, it is difficult for the power supply modules of existing calibration systems to be flexibly adapted, and there are often situations of unstable power supply or even inability to work. In addition, for the state diagnosis of voltage transformers, at present, it mostly relies on manual experience judgment, lacking scientific data support and accurate diagnosis models. Facing a large number of voltage transformers with different models and various operating conditions, it is difficult for traditional experience judgment to timely and accurately detect potential faults, posing safety hazards to the operation of power systems.

[0004] In view of the above problems, the present invention proposes a solution. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a on-site calibration system and a state diagnosis method for a voltage transformer, which solve the problems raised in the above background art through on-site calibration and state diagnosis of the voltage transformer.

[0006] To achieve the above object, the present invention provides the following technical solutions: A on-site calibration system and a state diagnosis method for a voltage transformer, including the following steps: Measure the primary voltage and secondary voltage of the standard voltage transformer, and calculate the voltage transformer ratio and the phase difference of the standard voltage transformer according to the primary voltage and secondary voltage of the standard voltage transformer; Obtain the secondary voltage of the voltage transformer by combining the primary voltage of the voltage transformer and the voltage transformer ratio and adaptively adjusting the frequency, and obtain the phase difference of the voltage transformer by combining the primary voltage of the voltage transformer; Calculate the voltage error rate according to the secondary voltage of the standard voltage transformer and the secondary voltage of the voltage transformer, construct a comprehensive verification index model by combining the phase difference of the standard voltage transformer and the phase difference of the voltage transformer, and obtain the on-site verification coefficient of the voltage transformer; Collect the working state data of the voltage transformer, construct a state diagnosis model using the support vector machine algorithm by combining the on-site verification coefficient of the voltage transformer to obtain the state diagnosis coefficient, and compare and analyze the state diagnosis coefficient with the state diagnosis threshold to diagnose whether there is an abnormality in the state of the voltage sensor.

[0007] In a preferred embodiment, the process of calculating the phase difference of the standard voltage transformer is as follows: Collect the signals of the primary voltage and secondary voltage to obtain a discrete voltage signal sequence and , where n is the sampling point number; Preprocess the collected voltage signals, including filtering and denoising operations; Perform Fourier transform on the preprocessed voltage signals to obtain the spectra of the primary voltage and secondary voltage signals respectively and , where k is the frequency component number; Extract the phases of the fundamental components of the primary voltage and secondary voltage from the spectra and ; According to the phases of the fundamental components of the primary voltage and secondary voltage and Calculate the phase difference of the standard voltage transformer , and the formula is: .

[0008] In a preferred embodiment, the process of the adaptive adjustment of the frequency is as follows: Sample the primary voltage at the initial sampling frequency to obtain a discrete primary voltage sequence , where N is the number of sampling points; Perform spectrum analysis on the collected primary voltage sequence, use the fast Fourier transform to obtain the spectrum of the signal, and analyze the frequency components and intensity distribution of the interference signals in the spectrum; Determine the interference frequency range according to the frequency components and intensity distribution of the interference signal and the interference signal intensity; And obtain the corresponding spectrum index according to the main interference frequency range, and determine the adjusted sampling frequency in combination with the interference signal intensity and the initial sampling frequency. The calculation formula is as follows: , In the formula, is the adjusted sampling frequency; is the initial sampling frequency; is the interference signal intensity; is the reference interference signal intensity; the spectrum of the signal; are the interference frequencies corresponding spectrum indices respectively; , are adjustment coefficients.

[0009] In a preferred embodiment, the process of obtaining the interference signal intensity is as follows: For narrowband interference, directly read the amplitude value of the interference signal at its center frequency as a measure of the interference signal intensity; For broadband interference, it is necessary to perform an integral calculation on the power within the frequency band occupied by the interference signal to obtain the interference signal intensity. The specific process is as follows: Measure the power spectral density function through a spectrum analyzer, and obtain the interference signal intensity through integral calculation in combination with the main interference frequency range. The specific calculation formula is as follows: , In the formula, is the interference signal intensity, and the interference frequency range is , is the power spectral density function.

[0010] In a preferred embodiment, the specific process of obtaining the phase difference of the voltage transformer is as follows: Find the zero-crossing points of the new primary voltage sequence and the secondary voltage sequence of the voltage transformer by comparing the signs of adjacent sampling points respectively; Record the sampling moments and of the adjacent zero-crossing points of the primary voltage and the secondary voltage signals, and calculate the phase difference of the voltage transformer in combination with the period t of the signal. The formula is .

[0011] In a preferred embodiment, the process of obtaining the secondary voltage sequence is as follows: Measure the ambient temperature and humidity during the first voltage measurement. Combine the new first voltage sequence and the voltage transformer ratio to calculate the secondary voltage sequence of the voltage transformer. The specific calculation formula is as follows: , In the formula, is the secondary voltage sequence of the voltage transformer, is the new first voltage sequence, N is the number of sampling points, B is the voltage transformer ratio, T is the ambient temperature, is the ambient temperature reference value, is the ambient humidity, is the ambient humidity reference value, 、 are the ambient temperature and humidity weight coefficients respectively. In a preferred embodiment, the expression of the comprehensive verification index model is: , In the formula, X is the on-site verification coefficient of the voltage transformer, is the phase difference of the standard voltage transformer, is the phase difference of the voltage transformer, w is the voltage error rate, , , is the verification index, determined by historical verification data.

[0012] In a preferred embodiment, the working state data includes the current fluctuation coefficient and the load power factor change rate; The process of obtaining the current fluctuation coefficient is as follows: In the secondary circuit of the voltage transformer, a high-precision current transformer is connected in series to collect the load current in real time, and the load current sequence ; According to the load current sequence, obtain the maximum and minimum values of the load current, and calculate the average value of the load current to obtain the current fluctuation coefficient. The specific calculation formula is as follows: , In the formula, is the current fluctuation coefficient, is the average value of the load current, is the maximum value of the load current, is the minimum value of the load current; The process of obtaining the load power factor change rate is as follows: Use a power factor meter and power calculation to calculate the load power factor at multiple time points. Calculate the load power factor change rate according to the load power factor and the time points. The formula is as follows: , In the formula, is the load power factor change rate, is the load power factor of the (k + 1)-th measurement, is the time point of the (k + 1)-th measurement, is the load power factor of the k-th measurement, is the time point of the k-th measurement.

[0013] In a preferred embodiment, the process of obtaining the state diagnosis coefficient is as follows: Combine the current fluctuation coefficient, the load power factor change rate, and the on-site calibration coefficient of the voltage transformer into a feature vector A; Label each feature vector with the corresponding state category y, with the normal state marked as +1 and the abnormal state marked as -1; And form a data set with the feature vector A and the corresponding state category y, and divide the data set into a training set and a test set according to a certain ratio; Based on the sequential minimal optimization algorithm, obtain the decision function values of the samples in the test set, and calculate the absolute value of the decision function values to obtain the state diagnosis coefficient.

[0014] In a preferred embodiment, the process of comparing the state diagnosis coefficient with the state diagnosis threshold to diagnose whether there is an abnormality in the voltage sensor state is as follows: Compare the calculated state diagnosis coefficient with the state diagnosis threshold: If the state diagnosis coefficient is greater than or equal to the state diagnosis threshold, it is diagnosed that the voltage sensor state is normal; If the state diagnosis coefficient is less than or equal to the state diagnosis threshold, it is diagnosed that the voltage sensor state is abnormal, analyze the reasons for the abnormal state of the voltage sensor, and take corresponding maintenance measures.

[0015] The technical effects and advantages of the on-site calibration system and state diagnosis method for a voltage transformer of the present invention: 1. The present invention constructs a comprehensive verification index by simultaneously collecting parameters such as the primary voltage, secondary voltage, and phase difference of a voltage transformer. Compared with the traditional verification method that only relies on the comparison of a single voltage parameter, the present invention comprehensively considers multiple key performance indicators of the voltage transformer. This method of multi-parameter fusion can more accurately reflect the true performance of the voltage transformer, greatly improve the accuracy of the verification results, and effectively reduce the operation risks of the power system caused by inaccurate verification. Advanced measuring equipment and complex calculation formulas are adopted in the process of measuring the parameters of the standard voltage transformer and subsequent calculation of the transformation ratio, phase difference, etc. For example, when measuring the primary voltage and secondary voltage, high-precision voltage sensors are selected, and signal preprocessing is carried out, including operations such as filtering, denoising, and environmental correction. When calculating the transformation ratio, the statistical analysis of the instantaneous transformation ratio sequence is carried out, and the weighted average method is used to determine the final transformation ratio, making the transformation ratio calculation more accurate. In the calculation of the phase difference, algorithms such as Hilbert transform and Kalman filter are used to effectively reduce the influence of measurement errors and interference, further improving the accuracy of the verification. The verification system can monitor the on-site electromagnetic environment in real time. According to the main frequency component range of the interference signal, the sampling frequency is adaptively adjusted through a formula. In a complex electromagnetic environment, the verification system with a traditional fixed sampling frequency is easily interfered, resulting in inaccurate sampling data, which in turn affects the verification results. The adaptive sampling frequency adjustment mechanism of the present invention can conduct more intensive sampling on the sensitive frequency band of the interference signal, effectively reducing the influence of interference on the verification data, ensuring that the signals of the voltage transformer can be accurately collected in various complex electromagnetic environments, and improving the reliability and stability of the verification system. The power supply module of the verification system can monitor the input power supply voltage in real time according to different on-site power supply situations through a formula and dynamically adjust the transformation ratio to ensure that a stable voltage is output to supply power to each part of the system. In the actual power system site, the power supply situation is complex and changeable, and problems such as voltage fluctuations and harmonics may exist. The adaptive adjustment function of the power supply module of the present invention enables the verification system to work normally under different power supply conditions, avoiding verification interruption or data errors caused by unstable power supply, and enhancing the environmental adaptability of the verification system.

[0016] 2. The present invention collects a large amount of historical calibration data and operating status data of voltage transformers under different models, operating times, and working conditions by using big data analysis technology, including parameters such as voltage error, phase error, ambient temperature, operating duration, load characteristics, and insulation performance. A state diagnosis model is constructed using the support vector machine algorithm. By finding the optimal classification hyperplane, the data in the low-dimensional space is mapped to the high-dimensional space for classification. Compared with the traditional state diagnosis method that relies on manual experience judgment, the diagnosis model based on big data and advanced algorithms of the present invention can analyze the operating status of voltage transformers more comprehensively and accurately, give early warnings of potential faults, and improve the safety and reliability of the power system. The state diagnosis coefficient is obtained through the state diagnosis model and compared with the pre-set state diagnosis threshold for analysis to determine whether there is an abnormality in the voltage transformer. This quantitative diagnosis method has clear judgment criteria, avoids the influence of subjective factors, and improves the accuracy and consistency of the diagnosis results. At the same time, according to different application scenarios and the importance of voltage transformers, the state diagnosis threshold can be flexibly adjusted to achieve personalized state diagnosis and better meet the actual needs of power system operation and maintenance. The present invention integrates the on-site calibration and state diagnosis functions of voltage transformers in one system, reducing the cumbersome steps of using multiple independent devices and performing multiple operations in the traditional calibration and diagnosis processes. The staff can complete all the work from calibration to diagnosis on one system platform, greatly improving work efficiency and saving time and labor costs. Through accurate state diagnosis, potential faults of voltage transformers can be detected in advance, maintenance measures can be taken in a timely manner, and power outages and equipment damage caused by equipment failures can be avoided. This not only reduces the economic losses caused by power outages but also reduces the costs of equipment maintenance and replacement, realizing preventive maintenance of the power system and improving the overall economic benefits of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of an on-site calibration system and state diagnosis method for a voltage transformer according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] Embodiment 1, Figure 1 An on-site calibration system and state diagnosis method for a voltage transformer according to the present invention are given.

[0020] Measure the primary voltage and secondary voltage of the standard voltage transformer, and calculate the voltage transformer ratio and the phase difference of the standard voltage transformer based on the primary voltage and secondary voltage of the standard voltage transformer; The process of measuring the primary voltage and secondary voltage of the standard voltage transformer is as follows: Select a high-precision voltage measuring device to measure the primary voltage and secondary voltage of the standard voltage transformer; Connect the measuring device to the primary side and secondary side of the standard voltage transformer; It should be noted that when connecting, it is necessary to strictly follow the electrical safety specifications to ensure good electrical connection between the measuring device and the voltage transformer, and avoid problems such as poor contact or short circuit; Under the condition that the standard voltage transformer is operating normally, start the measuring device and record the measured values of the primary voltage and secondary voltage; To improve the measurement accuracy, perform multiple measurements and take the average value as the final measurement result.

[0021] The specific process of calculating the voltage transformer ratio based on the primary voltage and secondary voltage of the standard voltage transformer is as follows: Obtain the voltage transformer ratio by calculating the ratio of the primary voltage to the secondary voltage of the standard voltage transformer; The voltage transformer ratio reflects the ability of the voltage transformer to convert high voltage to low voltage. The specific calculation formula is as follows: , In the formula, B is the voltage transformer ratio, is the measured value of the primary voltage of the standard voltage transformer, is the measured value of the secondary voltage of the standard voltage transformer.

[0022] The process of calculating the phase difference of the standard voltage transformer is as follows: Use a data acquisition system to collect the signals of the primary voltage and secondary voltage to obtain discrete voltage signal sequences and , where n is the sampling point number; Preprocess the collected voltage signals, including filtering and denoising operations, to improve the signal quality; Perform Fourier transform on the preprocessed voltage signals to obtain the spectra of the primary voltage and secondary voltage signals respectively and , where k is the frequency component number; Extract the phases of the fundamental components of the primary voltage and secondary voltage from the spectra and ; According to the phases of the fundamental components of the primary voltage and secondary voltage and Calculating the phase difference of a standard voltage transformer , the formula is: .

[0023] Obtain the secondary voltage of the voltage transformer by combining the primary voltage of the voltage transformer and the voltage transformer ratio and adaptively adjusting the frequency, and obtain the phase difference of the voltage transformer by combining the primary voltage of the voltage transformer; Connect a high-precision voltage sensor to the primary side of the voltage transformer, and use a certain initial sampling frequency to sample the primary voltage to obtain a discrete primary voltage sequence , where N is the number of sampling points; Perform spectral analysis on the collected primary voltage sequence, use the fast Fourier transform to obtain the spectrum of the signal, and analyze the frequency components and intensity distribution of the interference signals in the spectrum; Determine the interference frequency range and the interference signal intensity according to the frequency components and intensity distribution of the interference signals; The process of obtaining the interference signal intensity is as follows: For narrowband interference, directly read the amplitude value of the interference signal at its center frequency as a measure of the interference signal intensity; For broadband interference, it is necessary to perform integral calculation on the power within the frequency band occupied by the interference signal to obtain the interference signal intensity. The specific process is as follows: Measure the power spectral density function through a spectrum analyzer, and obtain the interference signal intensity through integral calculation in combination with the main interference frequency range. The specific calculation formula is as follows: , In the formula, is the interference signal intensity, and the interference frequency range is , is the power spectral density function; And obtain the corresponding spectrum index according to the main interference frequency range, and determine the adjusted sampling frequency in combination with the interference signal intensity and the initial sampling frequency. The calculation formula is as follows: , In the formula, is the adjusted sampling frequency; is the initial sampling frequency; is the interference signal intensity; is the reference interference signal intensity; the spectrum of the signal; are the interference frequencies corresponding spectrum indices respectively; 、 is an adjustment coefficient that needs to be calibrated and determined according to the actual situation; Re - collect the primary voltage of the voltage transformer using the adjusted sampling frequency to obtain a new primary voltage sequence ; The characteristics of the primary voltage signal can be captured more accurately, reducing the influence of interference; When calculating the secondary voltage, not only the transformation ratio k of the voltage transformer needs to be considered, but also the influence of environmental factors on the transformation ratio; Obtain the environmental temperature and humidity when measuring the primary voltage, and calculate the secondary voltage sequence of the voltage transformer in combination with the new primary voltage sequence and the transformation ratio of the voltage transformer. The specific calculation formula is as follows: , In the formula, is the secondary voltage sequence of the voltage transformer, is the new primary voltage sequence, N is the number of sampling points, B is the transformation ratio of the voltage transformer, T is the environmental temperature, is the reference value of the environmental temperature, is the environmental humidity, is the reference value of the environmental humidity, , are the weight coefficients of environmental temperature and humidity respectively, determined by the historical environment.

[0024] According to the secondary voltage of the voltage transformer, the specific process of obtaining the phase difference of the voltage transformer in combination with the primary voltage of the voltage transformer is as follows: Find the zero - crossing points of the new primary voltage sequence and the secondary voltage sequence of the voltage transformer respectively by comparing the signs of adjacent sampling points. The zero - crossing point refers to the point where the signal crosses the zero level from negative to positive or from positive to negative; Record the sampling moments of adjacent zero - crossing points of the primary voltage and secondary voltage signals and , and calculate the phase difference of the voltage transformer in combination with the period t of the signal. The formula is .

[0025] Calculate the voltage error rate according to the secondary voltage of the standard voltage transformer and the secondary voltage of the voltage transformer, and construct a comprehensive calibration index model in combination with the phase difference of the standard voltage transformer and the phase difference of the voltage transformer to obtain the on - site calibration coefficient of the voltage transformer; Calculate the secondary voltage of the voltage transformer by weighted summation of the secondary voltage sequence of the voltage transformer, and calculate the voltage error rate in combination with the secondary voltage of the standard voltage transformer. The specific formula is as follows: , In the formula, is the voltage error rate, is the secondary voltage of the standard voltage transformer, is the secondary voltage of the voltage transformer; The expression of the comprehensive verification index model is: , where X is the on-site verification coefficient of the voltage transformer, is the phase difference of the standard voltage transformer, is the phase difference of the voltage transformer, w is the voltage error rate, , , is the verification index, which is determined by historical verification data.

[0026] It should be noted that constructing the comprehensive verification index model and obtaining the on-site verification coefficient of the voltage transformer have important roles in many aspects, which are mainly reflected in the following aspects: Accurately evaluate the performance of the transformer: The performance evaluation of the voltage transformer cannot rely solely on a single index. The comprehensive verification index model takes into account multiple key factors such as the voltage error rate and the phase difference. By reasonably integrating these factors, the obtained on-site verification coefficient can comprehensively and accurately reflect the comprehensive performance of the voltage transformer under actual operating conditions, including the accuracy of its transformation ratio and phase characteristics, etc., so as to more accurately judge whether the transformer meets the operating requirements of the power system.

[0027] Improve the verification accuracy: Traditional verification methods may only focus on some parameters and easily ignore some factors that have important impacts on the performance of the transformer, resulting in deviations in the verification results. The comprehensive verification index model comprehensively analyzes multiple parameters through a mathematical model, can more comprehensively consider the mutual relationships between various factors, thus effectively improving the verification accuracy, reducing errors, and providing a more reliable guarantee for the safe and stable operation of the power system.

[0028] Facilitate fault diagnosis and location: When the voltage transformer shows abnormalities, the verification coefficient obtained from the comprehensive verification index model can help the staff more quickly locate the type and location of the fault. For example, if the voltage error rate and the phase difference show abnormalities, by analyzing the changes in the verification coefficient and the relationships between various parameters, it can be judged whether there are faults in the windings, cores or other related components of the transformer, providing a strong basis for subsequent maintenance and debugging, shortening the fault handling time, and improving the reliability of the power system.

[0029] Provide a basis for status evaluation: Combining the operating status data of the voltage transformer, the on-site calibration coefficient is an important basis for constructing a status diagnosis model. It provides a quantitative index for status diagnosis. By comparing with historical data and the standard values under normal operating conditions, the performance change trend of the voltage transformer can be detected in a timely manner, potential fault risks can be predicted in advance, the status monitoring and preventive maintenance of the voltage transformer can be realized, the operation risk of the power system can be reduced, and the service life and operation efficiency of the equipment can be improved.

[0030] Meet the requirements of different application scenarios: Different application scenarios of the power system may have different performance requirements for the voltage transformer. The comprehensive calibration index model can adjust the weights of each parameter according to the specific application scenario and requirements, so as to obtain the on-site calibration coefficient suitable for a specific scenario. This can ensure that the performance of the voltage transformer can be accurately evaluated under different working conditions, meeting the diverse operation needs of the power system.

[0031] Collect the operating status data of the voltage transformer, and use the support vector machine algorithm to construct a status diagnosis model with the on-site calibration coefficient of the voltage transformer to obtain the status diagnosis coefficient. Compare and analyze the status diagnosis coefficient with the status diagnosis threshold to diagnose whether there is an abnormality in the status of the voltage sensor.

[0032] The operating status data includes the current fluctuation coefficient and the load power factor change rate; The process of obtaining the current fluctuation coefficient is as follows: In the secondary circuit of the voltage transformer, a high-precision current transformer is connected in series to collect the load current in real time, and a load current sequence is obtained ; Obtain the maximum and minimum values of the load current according to the load current sequence, and calculate the average value of the load current to obtain the current fluctuation coefficient. The specific calculation formula is as follows: , In the formula, is the current fluctuation coefficient, is the average value of the load current, is the maximum value of the load current, is the minimum value of the load current; The process of obtaining the load power factor change rate is as follows: Use a power factor meter to calculate the load power factor at multiple time points in combination with power. Calculate the load power factor change rate according to the load power factor and the time points. The formula is as follows: , In the formula, is the load power factor change rate, is the load power factor measured at the (k + 1)th time, is the time point of the (k + 1)-th measurement, is the load power factor of the k-th measurement, is the time point of the k-th measurement.

[0033] Combine the current fluctuation coefficient, the change rate of load power factor, and the on-site calibration coefficient of the voltage transformer into the feature vector A; Label the corresponding state category y for each feature vector, with the normal state marked as +1 and the abnormal state marked as -1; And form a data set with the feature vector A and the corresponding state category y, and divide the data set into a training set and a test set according to a certain ratio; Based on the sequential minimal optimization algorithm, obtain the decision function values of the samples in the test set, and calculate the absolute value of the decision function values to obtain the state diagnosis coefficient.

[0034] By analyzing the training set and a large amount of historical data, use methods such as cross-validation and receiver operating characteristic curve (ROC) analysis to determine a suitable state diagnosis threshold.

[0035] Compare the calculated state diagnosis coefficient with the state diagnosis threshold: If the state diagnosis coefficient is greater than or equal to the state diagnosis threshold, it is diagnosed that the state of the voltage sensor is normal; If the state diagnosis coefficient is less than or equal to the state diagnosis threshold, it is diagnosed that the state of the voltage sensor is abnormal, and analyze the specific reasons for the abnormal state of the voltage sensor in order to take corresponding maintenance measures.

[0036] The above formulas are all dimensionless and take their numerical values for calculation. The formula is obtained by software simulation of a large amount of collected data to get a formula closest to the actual situation. The preset parameters in the formula are set by those skilled in the art according to the actual situation.

[0037] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any other combination. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product.

[0038] Those of ordinary skill in the art can realize that the modules and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0039] In addition, in each embodiment of the present application, each functional module may be integrated into a processing module, may exist physically alone for each module, or two or more modules may be integrated into one module.

[0040] As described above, the above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0041] Finally: The above is only the preferred embodiment of the present invention and is not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A voltage transformer on-site calibration system and status diagnosis method, characterized in that: The following steps are involved: Measure the primary voltage and secondary voltage of the standard voltage transformer, and calculate the voltage transformer ratio and the standard voltage transformer phase difference according to the primary voltage and secondary voltage of the standard voltage transformer; The secondary voltage of the voltage transformer is obtained according to the primary voltage of the voltage transformer and the transformation ratio of the voltage transformer in combination with the adaptive frequency adjustment, and the phase difference of the voltage transformer is obtained in combination with the primary voltage of the voltage transformer; The voltage error rate is calculated based on the standard voltage transformer secondary voltage and the voltage transformer secondary voltage, and a comprehensive calibration index model is constructed by combining the standard voltage transformer phase difference and the voltage transformer phase difference to obtain the voltage transformer on-site calibration coefficient; The working status data of the voltage transformer is collected, and the support vector machine algorithm is used to build a status diagnosis model in combination with the on-site calibration coefficient of the voltage transformer to obtain the status diagnosis coefficient. The status diagnosis coefficient is compared and analyzed with the status diagnosis threshold to diagnose whether there is any abnormality in the voltage sensor status.

2. A voltage transformer on-site calibration system and status diagnosis method according to claim 1, characterized in that: The process of calculating the standard voltage transformer phase difference is as follows: The primary and secondary voltage signals are collected to obtain discrete voltage signal sequences. and , where n is the sampling point number; Preprocess the collected voltage signal, including filtering and denoising operations; Perform Fourier transform on the preprocessed voltage signal to obtain the frequency spectrum of the primary voltage and secondary voltage signals respectively. and , where k is the frequency component number; Extract the phase of the fundamental components of the primary and secondary voltages from the spectrum and ; According to the phase of the fundamental component of the primary voltage and the secondary voltage and Calculating the phase difference of a standard voltage transformer , the formula is: .

3. A voltage transformer on-site calibration system and status diagnosis method according to claim 2, characterized in that: The process of adaptively adjusting the frequency is as follows: At the initial sampling frequency For primary voltage Sampling is performed to obtain a discrete voltage sequence ,in N is the number of sampling points; Perform spectrum analysis on the collected primary voltage sequence, use fast Fourier transform to obtain the spectrum of the signal, and analyze the frequency components and intensity distribution of the interference signal in the spectrum; Determine the interference frequency range based on the frequency components and intensity distribution of the interference signal and the interference signal strength; And obtain the corresponding spectrum index according to the main interference frequency range, and adjust the sampling frequency based on the interference signal strength and the initial sampling frequency. The calculation formula is as follows: , In the formula, is to adjust the sampling frequency; is the initial sampling frequency; is the interference signal strength; is the reference interference signal strength; The spectrum of the signal; The interference frequencies are The corresponding spectrum index; , is the adjustment factor.

4. A voltage transformer on-site calibration system and status diagnosis method according to claim 3, characterized in that: The interference signal strength acquisition process is as follows: For narrowband interference, the amplitude value of the interference signal at its center frequency is directly read as a measure of the interference signal strength; For broadband interference, it is necessary to integrate the power in the frequency band occupied by the interference signal to obtain the interference signal strength. The specific process is as follows: The power spectrum density function is measured by a spectrum analyzer, and the interference signal strength is obtained by integration calculation based on the main interference frequency range. The specific calculation formula is as follows: , In the formula, is the interference signal strength, and the interference frequency range is , is the power spectral density function.

5. A voltage transformer on-site calibration system and status diagnosis method according to claim 4, characterized in that: The specific process of obtaining the voltage transformer phase difference is as follows: By comparing the signs of adjacent sampling points, the zero-crossing points of the new primary voltage sequence and the secondary voltage sequence of the voltage transformer are found respectively; Record the sampling time of the adjacent zero-crossing points of the primary and secondary voltage signals and , combined with the signal period t to calculate the voltage transformer phase difference, the formula is .

6. A voltage transformer on-site calibration system and status diagnosis method according to claim 5, characterized in that: The secondary voltage sequence acquisition process is as follows: The ambient temperature and humidity when measuring the primary voltage are combined with the new primary voltage sequence and the voltage transformer ratio to calculate the voltage transformer secondary voltage sequence. The specific calculation formula is as follows: , In the formula, is the voltage transformer secondary voltage sequence, is the new primary voltage sequence, N is the number of sampling points, B is the voltage transformer ratio, T is the ambient temperature, is the ambient temperature reference value, is the ambient humidity, is the ambient humidity reference value, , are the weight coefficients of ambient temperature and humidity respectively.

7. A voltage transformer on-site calibration system and status diagnosis method according to claim 6, characterized in that: The expression of the comprehensive verification index model is: , Where X is the voltage transformer field calibration coefficient, is the standard voltage transformer phase difference, is the voltage transformer phase difference, w is the voltage error rate, , , is the calibration index, determined by historical calibration data.

8. A voltage transformer on-site calibration system and status diagnosis method according to claim 7, characterized in that: The working status data includes current fluctuation coefficient and load power factor change rate; The current fluctuation coefficient acquisition process is as follows: In the secondary side circuit of the voltage transformer, a high-precision current transformer is connected in series to collect the load current in real time and obtain the load current sequence ; According to the load current sequence, the maximum and minimum values ​​of the load current are obtained, and the average value of the load current is calculated to obtain the current fluctuation coefficient. The specific calculation formula is as follows: , In the formula, is the current fluctuation coefficient, The average load current, is the maximum load current, is the minimum load current; The load power factor change rate acquisition process is as follows: Use a power factor meter combined with power to calculate the load power factor at multiple time points, and calculate the load power factor change rate based on the load power factor and time point. The formula is as follows: , In the formula, is the load power factor change rate, is the load power factor measured for the k+1th time, is the time point of the k+1th measurement, is the load power factor measured for the kth time, is the time point of the kth measurement.

9. A voltage transformer on-site calibration system and status diagnosis method according to claim 8, characterized in that: The process of obtaining the status diagnosis coefficient is as follows: The current fluctuation coefficient, the load power factor change rate and the voltage transformer field calibration coefficient are combined into a characteristic vector A; Label each feature vector with the corresponding state category y, where the normal state is marked as +1 and the abnormal state is marked as -1; The feature vector A and the corresponding state category y form a data set, and the data set is divided into a training set and a test set according to a certain ratio; The decision function value of the samples in the test set is obtained based on the sequence minimum optimization algorithm, and the absolute value of the decision function value is calculated to obtain the state diagnosis coefficient.

10. A voltage transformer on-site calibration system and status diagnosis method according to claim 9, characterized in that: The process of comparing and analyzing the state diagnosis coefficient and the state diagnosis threshold to diagnose whether the voltage sensor state is abnormal is as follows: Compare the calculated state diagnosis coefficient with the state diagnosis threshold: If the state diagnosis coefficient is greater than or equal to the state diagnosis threshold, the state of the diagnosis voltage sensor is not abnormal; If the status diagnosis coefficient is less than or equal to the status diagnosis threshold, it is diagnosed that the voltage sensor status is abnormal, and the cause of the abnormal voltage sensor status is analyzed, and corresponding maintenance measures are taken.

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