4.1.5.10 Technical revision historyTable 236:T1PTTR Technical revision historyTechnical revision ChangeC Removed theSensor available setting parameterD Added the AMB_TEMP input4.1.6 Three-phase thermal overload protection for powertransformers, two time constants T2PTTR4.1.6.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberThree-phase thermal overloadprotection for power transformers, twotime constantsT2PTTR 3Ith>T 49T4.1.6.2 Function blockGUID-68AADF30-9DC7-49D5-8C77-14E774C8D1AF V2 ENFigure 117: Function block4.1.6.3 FunctionalityThe three-phase thermal overload, two time constant protection function T2PTTRprotects the transformer mainly from short-time overloads. The transformer isprotected from long-time overloads with the oil temperature detector included in itsequipment.The alarm signal gives an early warning to allow the operators to take action beforethe transformer trips. The early warning is based on the three-phase currentmeasuring function using a thermal model with two settable time constants. If thetemperature rise continues, T2PTTR operates based on the thermal model of thetransformer.After a thermal overload operation, the re-energizing of the transformer is inhibitedduring the transformer cooling time. The transformer cooling is estimated with athermal model.Section 4 1YHT530004D05 DProtection functions232 615 seriesTechnical Manual
