Patent ID: 10389107

Abstract:
The invention is concerned with a protection device, method and computer program product for protecting a transformer including a tap changer and a transformer arrangement including a transformer and a protection device. The transformer has at least two magnetically coupled windings with terminals (MT1, MT2, MT3, MT4) at which power enters and exits the transformer and a tap changer having impedance elements and a switch configured to gradually connect the impedance elements when changing between two tap changer positions during a tap changing operation. The method is performed in the protection device and includes: obtaining measurements of power transmission properties (Iin, Uin, Iout, Uout) at the magnetically coupled windings, estimating energy deposited in the impedance elements during a tap changing operation based on the measured physical properties, comparing the estimated deposited energy with a failure threshold, and protecting the transformer in case the threshold is exceeded, wherein the estimating of the deposited energy includes determining the power loss of the transformer between the terminals (MT1, MT2) where power enters and the terminals (MT3, MT4) where power leaves the transformer and integrating the power loss.