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The traceability method directly affects the reliability and accuracy of the measurement of electronic transformers. The stability and unreliable traceability performance of analog devices would affect the traditional analog differential... more
The traceability method directly affects the reliability and accuracy of the measurement of electronic transformers. The stability and unreliable traceability performance of analog devices would affect the traditional analog differential method. Thus, we propose a digital differential method combining a time series-weighted correlation degree extension integrating Hilbert phase-shift of four-term continuous third-derivative Nuttall window function, effectively suppressing the end effect problem and realizing the high-precision addition of the differential. Results of simulation experiments showed that the differential’s deviation was <10−10, much less than that (1.32 × 10−4) due to the analog differential. The voltage and current ratio difference’s combined standard uncertainty was 5.01 × 10−5 and 5.08 × 10−5, respectively, and 0.1718′ in the phase error. Finally, an automatic traceability detection system was constructed. Compared with the traditional method, the accuracy and st...
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The calibration method of electronic transformer is one of the key technologies to ensure the gradual improvement of reliability and accuracy. For the phenomenon that the electronic transformer is affected by working condition, the... more
The calibration method of electronic transformer is one of the key technologies to ensure the gradual improvement of reliability and accuracy. For the phenomenon that the electronic transformer is affected by working condition, the measurement signal contains harmonics, noise and frequency fluctuation, a calibration method based on correlation and lattice notch filter is proposed. The simplified adaptive lattice notch filter is used to preprocess the collected data and extract frequency, filter out the interference of harmonics and noise, and improve the precision of the ratio error. And the interpolation correlation method which is not sensitive to noise and harmonic is used to calculate the phase difference. For the non integral period sampling caused by frequency fluctuation, the sampling data is interpolated according to the size of frequency offset. This process achieves the integral period sampling and further improve the calibration precision of angle error. Simulation result...
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The capacitor voltage transformer is now widely used in the high-voltage grid and its ratio error drift is one of the major fault developed from the maintenance experience. Thus, monitoring its ratio error drift efficiently attracts great... more
The capacitor voltage transformer is now widely used in the high-voltage grid and its ratio error drift is one of the major fault developed from the maintenance experience. Thus, monitoring its ratio error drift efficiently attracts great interests. Conventional methods are time-consuming and need power cut, while some innovative data-driven methods are not so practical because of its rigorous precondition. Therefore, we propose a fuzzy modeling method for CVTs connected to the same phase along with the principal component analysis(PCA). Besides, the kernel density estimation(KDE) is also applied to improve its sensitivity. The KDE-PCA is more sensitive to the ratio error drift than the conventional PCA method as well as previous proposed methods through a field application in a 220kV thermal power plant.
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Capacitive voltage transformer (CVT) is a measurement device widely used in high-voltage power grids. Evaluating CVT's internal insulation online and replacing faulty device are critical for power grid's safety. However, the... more
Capacitive voltage transformer (CVT) is a measurement device widely used in high-voltage power grids. Evaluating CVT's internal insulation online and replacing faulty device are critical for power grid's safety. However, the existing online evaluation methods mainly relaying on installing auxiliary sensors inside the device, which may change its internal electric field distribution and makes the device easy to be broken. In response to these challenges, an online evaluation method for the internal insulation state of CVT based on its measurements is proposed. This method explores the internal connection between the internal insulation state of CVT and its measurement error information, and then inverts the change of the internal insulation state of the CVT by monitoring the change of the measurement information of the CVT, and realizes the real-time online evaluation of the internal insulation state of the CVT based on the support vector machine. Experimental analysis shows that this method can accurately evaluate the internal insulation state of the CVT without the need for power outages and external sensors.