Abstract
The electronic voltage transformer (EVT) has received much attention with the recent global trend to establish smart grids and digital substations. One of the main issues of the EVT is the deterioration of its performance with long-term operation which affects the control and protection systems it is employed for and hence the overall reliability of the power grids. This calls for the essential need for a reliable technique to regularly assess the accuracy of operating EVT in real-time. Unfortunately, traditional calibration methods cannot detect the incipient EVT performance change in real-time. As such, this paper presents a new online method to evaluate the accuracy of the EVT. In this regard, the Q-statistic is calculated based on the recursive principal components analysis (RPCA) using the output data of EVT to map up the changes of metering error on the electric–physics relationship. By employing the output data of the EVT along with the power grid characteristics, the performance of the EVT is evaluated without the need for a standard transformer, as per the current industry practice. Results show that the proposed method can assess the EVT with a 0.2 accuracy class.
Highlights
The electronic voltage transformer (EVT) is a metering device that comprises a sensing element and data processing unit
The main issue of the EVT is its poor stability over a long-term operation which calls for further improvement
As can be seen from (2), the output of the EVT includes the data of the power grid which is linearly correlated with xt along with the EVT measurement errors that are nonlinearly correlated with xt
Summary
The electronic voltage transformer (EVT) is a metering device that comprises a sensing element and data processing unit. Energies 2020, 13, 5576 or two years, using equipment containing a standard transformer [9,10] This offline calibration method calls for the disconnection of the operating EVT which causes an interruption to the power grids. In the expected harsh operating environment of high voltage and strong magnetic field, the issue of accuracy degradation of the calibration system itself may arise due to its electromagnetic or capacitance-based structure. This has motivated researchers to come up with new calibration systems without using a standard voltage transformer. The correlation between the power grid characteristics and the output data of the EVT is investigated and a new online evaluation technique without using a standard voltage transformer is developed
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