Inductive coupling method for on-line frequency response analysis (FRA) for transformer winding diagnostic

Based on two-probe inductive coupling and two-port cascade network theorem, in-circuit impedance extraction of primary of operational transformer has been discussed and validated. The importance of this approach is to overcome drawbacks in existing on-line Frequency Response Analysis (FRA) which is used to monitor impedance of the transformer winding to detect movement or deformation of transformer winding and predict early sign of transformer failure. Hence, it can be used for on-line FRA on operational transformer without expensive outage of the system.