Research on the reliability of capacitor voltage transformers calibration results

The capacitor voltage transformer (CVT) is one of the most important measurement equipment in the power system, and its measurement accuracy is a key factor to ensure the safety of the power system and the fairness of electricity trade. To ensure the steady-state measurement accuracy, the conventional calibration is carried out to CVTs before operating in substations, and the operating CVTs must be calibrated periodically. However, excessive measurement error often occurs to CVTs which have passed the calibrations. In this paper, the reasons for the inconsistency between calibration results and actual measurement errors are proposed. The calibration in the laboratory, on-site calibration and three-phase operating CVTs are simulated according to actual operating conditions. Both the theoretical analysis and simulation results demonstrate that significant differences exist between the actual measurement errors and the calibration results of CVTs. Some experiments corresponding to the simulations verify the conclusions above. Finally, some suggestions to improve the reliability of calibration results are given. (C) 2019 Elsevier Ltd. All rights reserved.