Detection of anomalies on substation protection using oscillography relays

This work elucidates how the authors detected a discoordination case involving overcurrent relays of a feeder and a electric energy substation transformer of AES Sul-Distribuidora Gaucha de Energia concession´s area, originating on the disregarding, on the protection adjust period, of the different load levels of distribution feeders and total current from the substation transformer. If the relays didn´t include an oscillographics option on substation digital protection, this problem probably would not be recognized. Also, the providences to this problem of bad coordination in the company are presented.