Digital Differential Protection of the «Generator-Transformer» Block

This article discusses methods of lowering the influence of aperiodic components on operation of digital relay protection of generators by units “generator-transformer”. We show that there are four possible selections for excluding the false operation of relay protection determined by saturation of magnetic conductors in current transformers and existence in short-circuit currents in aperiodic components. Features of relay protection of block “generator-transformer” in case of change of transformation coefficient of the transformer are considered. Authors propose the alternative method of separation of odd harmonics in currents of switching on of power transformers after switch-off of short circuits.