Single time constant(min)Short time constant (min)Long time constant (min)Weighting factor p50 5.1 82 0.455 5.6 90 0.460 6.1 98 0.465 6.7 107 0.470 7.2 115 0.475 7.8 124 0.4The default Max temperature setting is 105°C. This value is chosen since even thoughthe IEC 60076-7 standard recommends 98°C as the maximum allowable temperaturein long-time loading, the standard also states that a transformer can withstand theemergency loading for weeks or even months, which may produce the windingtemperature of 140°C. Therefore, 105°C is a safe maximum temperature value for atransformer if the Max temperature setting value is not given by the transformermanufacturer.4.1.5.7 SignalsTable 409:T2PTTR Input signalsName Type Default DescriptionI3P SIGNAL - Three-phase currentsBLOCK BOOLEAN 0=False Block signal for activating the blocking modeAMB_TEMP FLOAT32 0 The ambient temperature used in the calculationTable 410:T2PTTR Output signalsName Type DescriptionOPERATE BOOLEAN OperateSTART BOOLEAN StartALARM BOOLEAN Thermal AlarmBLK_CLOSE BOOLEAN Thermal overload indicator. To inhibite reclose.4.1.5.8 SettingsTable 411:T2PTTR Group settings (Basic)Parameter Values (Range) Unit Step Default DescriptionEnv temperature Set -50...100 °C 1 40 Ambient temperature used when noexternal temperature measurementavailableTemperature rise 0.0...200.0 °C 0.1 78.0 End temperature rise above ambientMax temperature 22.0...200.0 °C 0.1 105.0 Maximum temperature allowed for thetransformerTable continues on next page1MRS759142 C Section 4Protection functionsREX640 373Technical Manual
