Research into an Online Calibration System for the Errors of Voltage Transformers Based on Open–Closed Capacitor

Li, Zhenhua; Li, Qiuhui; Wu, Zhengtian; Li, Zhenxing

doi:10.3390/en11061455

Cited by 12 publications

(8 citation statements)

References 18 publications

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“…e VDR of the CVD is assumed to be approximately equal to that of the CVT. Besides, the VDR of the CVD depends mainly on the bulk capacitance, the stray capacitance of the CVD to ground and the high-voltage terminal [33][34][35][36].…”

Section: Structure and Operation Principle Of The Cvtmentioning

confidence: 99%

Studying the Effect of Stray Capacitance on the Measurement Accuracy of the CVT Based on the Boundary Element Method

et al. 2021

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The capacitive voltage transformer (CVT) is a special measuring and protecting device, which is commonly applied in high-voltage power systems. Its measurement accuracy is affected seriously by the stray capacitances of the capacitance voltage divider (CVD) to ground and other charged parts. In this study, based on the boundary element method, a mathematical model was established firstly to calculate the stray capacitance. Then, the voltage distribution of the CVD was obtained by the CVD’s equivalent circuit model. Next, the effect of stray capacitance on the voltage distribution and the voltage difference ratio (VDR) of CVD was analysed in detail. We finally designed three types of shield and optimized their structure parameters to reduce VDR. The results indicated that the average deviation rate between calculated and experimental measured voltages is only 0.015%; that is to say, the method has high calculation precision. The stray capacitance of the CVD to ground is far larger than that of the CVD to the high-voltage terminal. It results in the inhomogeneous distribution of voltage and the increase of VDR. For the test CVT, its VDR exceeds the requirement of class 0.2. Among all of the three types of shield, the C type reduced the VDR of the test CVT the most. After optimizing the structure parameters of C-type shield, the VDR is further reduced to 0.08%. It is not only in accord with the requirement of class 0.2 but also has an adequate margin.

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Section: Structure and Operation Principle Of The Cvtmentioning

confidence: 99%

Studying the Effect of Stray Capacitance on the Measurement Accuracy of the CVT Based on the Boundary Element Method

et al. 2021

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“…However, this method requires periodic power failure operations, and the standard transformer is inconvenient to transport. In [5], the author proposed a calibration method without power failure, but the safety of the operation is difficult to guarantee, and it still needs to be calibrated by standard transformers, which is difficult to be widely used.…”

Section: Introductionmentioning

confidence: 99%

Error Evaluation Method of Capacitive Voltage Transformer Based on Improved Principal Component Analysis

Zhao,

Wei

2023

J. Phys.: Conf. Ser.

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The capacitive voltage transformer is an important data source for electricity trading and is easily influenced by environmental factors during operation, resulting in decreased metering accuracy. Because the voltage data does not satisfy the Gaussian distribution, the accuracy of the traditional principal component analysis method is poor when evaluating the error of capacitive voltage transformers. This paper proposes an improved principal component analysis method based on the local outlier factor. First, principal component analysis is utilized to separate the primary voltage fluctuation and error change. Then, a new statistic is established by using the local outlier factor instead of the traditional statistic as an evaluation standard, which reduces the missed diagnosis and misdiagnosis caused by the data distribution characteristics. The experimental results show that the improved method is better than the traditional method in terms of the detection rate of transformer anomaly detection, can effectively detect the abnormal change of transformer error and is more suitable for capacitive voltage transformers in operation.

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“…Traditional blackout detection methods evaluate by measuring parameters such as insulation resistance, dielectric loss angle and partial discharge of the CVT under blackout conditions [5]. However, the disadvantage of this method is that it is not only impossible to track the operating status of the CVT in adjacent detection cycles, but also that each high-voltage bus connected to the CVT must be operating in a non-fault power outage during detection [6]. This affects the reliability of the power supply, the detection process is heavy and there are safety risks [7].…”

Section: Introductionmentioning

confidence: 99%

Online Evaluation Method of CVT Internal Insulation Abnormality Based on Self-Supervised Learning

He,

Zhou,

Tong

et al. 2023

Energies

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A capacitive voltage transformer (CVT) is one of the electrical quantities measurement devices, and the state of its internal insulation is the key factor for ensuring the accuracy of its measurement of electrical energy. In view of the fact that the traditional real-time evaluation method of a CVT internal insulation anomaly mainly relies on empirical rules and prior knowledge and lacks the ability to independently mine effective features, an online evaluation method of a CVT internal insulation anomaly based on self-supervised learning is proposed. Firstly, an autoencoder is constructed to extract the residual sequence of the CVT secondary voltage and eliminate the influence of primary voltage fluctuation and power system voltage regulation. Without any prior knowledge, the complex dependence of the residual sequences in time and feature dimensions is learned by using a parallel graph attention layer (GATv2). Finally, a joint optimization based on the prediction and reconstruction model is introduced to obtain the abnormal inference score at each timestamp and realize the evaluation of the CVT internal insulation status. Experimental analysis shows that this method can effectively eliminate the influence of primary voltage fluctuation and power system voltage regulation on the online evaluation of the CVT internal insulation status and independently excavate the abnormal characteristics of the CVT secondary voltage to realize real-time monitoring and early warning of the CVT internal insulation status.

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Research into an Online Calibration System for the Errors of Voltage Transformers Based on Open–Closed Capacitor

Cited by 12 publications

References 18 publications

Studying the Effect of Stray Capacitance on the Measurement Accuracy of the CVT Based on the Boundary Element Method

Studying the Effect of Stray Capacitance on the Measurement Accuracy of the CVT Based on the Boundary Element Method

Error Evaluation Method of Capacitive Voltage Transformer Based on Improved Principal Component Analysis

Online Evaluation Method of CVT Internal Insulation Abnormality Based on Self-Supervised Learning

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