An adaptive scheme for digital protection of power transformers

The development of an adaptive scheme for digital differential protection of power transformers is described. The transformer status is monitored to decide if the transformer is disconnected or is in normal operating condition. When the transformer is energized, a two-state Kalman filter model monitors the transformer during normal operating conditions. The current transformer ratios and tap values are included in the algorithm to obtain an adaptive percentage differential characteristic. This adaptive scheme was tested on data obtained in the laboratory and proved to be highly accurate and fast