4.3.2.2 Function blockGUID-134E8524-738D-4232-A6BD-4C9BD2A62F8D V1 ENFigure 204: Function block4.3.2.3 FunctionalityThe transformer differential protection TR2PTDF is designed to protect two-winding transformers and generator-transformer blocks. TR2PTDF includes lowbiased and high instantaneous stages.The biased low stage provides a fast clearance of faults while remaining stable withhigh currents passing through the protected zone increasing errors on currentmeasuring. The second harmonic restraint, together with the waveform basedalgorithms, ensures that the low stage does not operate due to the transformerinrush currents. The fifth harmonic restraint ensures that the low stage does notoperate on apparent differential current caused by a harmless transformer over-excitation.The instantaneous high stage provides a very fast clearance of severe faults with ahigh differential current regardless of their harmonics.The setting characteristic can be set more sensitive with the aid of tap changerposition compensation. The correction of transformation ratio due to the changes intap position is done automatically based on the tap changer status information.4.3.2.4 Operation principleThe function can be enabled and disabled with the Operation setting. Thecorresponding parameter values are "On" and "Off".The operation of transformer differential protection can be described by using amodule diagram. All the modules in the diagram are explained in the next sections.Section 4 1YHT530004D05 DProtection functions384 615 seriesTechnical Manual
