Consideration of Condition Monitoring Methods for Capacitor Voltage Transformers

Changes in the characteristics of the insulating materials that compose the Capacitor Voltage Transformers (CVT) or insulation abnormalities in the oil-impregnated paper capacitors in the CVT are manifested as changes in the CVT transformation ratio. In this paper, a diagnostic method based on the measurement of CVT secondary voltage was investigated. The change in the CVT secondary voltage (calculated value) in the event of a single element breakdown of oil-impregnated paper capacitors is sufficiently large compared to the dispersion in the secondary voltage (measured value) of actual CVTs used in the substation. It was shown that CVT diagnosis is possible by comparing the secondary voltages of CVTs connected to the same bus bar in the substation with each other. A concrete example of the CVT diagnosis flow when applied to an actual substation is also presented.