On-line Monitoring of Current Transformer Dielectric Loss Based on Absolute Measurement

CT (Current Transformer) is often used for current conversion in high voltage or extra high voltage grids, so the problem of insulation is very prominent. Since dielectric loss is very effective to judge deterioration and being moistened defects of current transformer, it can be detected by two individual currents. This paper proposes an on-line monitoring system of current transformer’s dielectric loss based on absolute measuring method. To guarantee the precision, active zero magnetic flux current sensor is developed. The data in the laboratory demonstrated that the uncertainty of system is less than 0.01%. The field data prove that the variation range of dielectric loss meets the requirements of CT operating normally. Compared to traditional technique, it improves the efficiency and guarantees the accuracy.