1MRS751802-MUM REX 521235Protection RelayTechnical Reference Manual, Standard Configurations11.7.2. MeasurementsThe following measurements are supported in this application example:• True RMS measurement of phase currents• True RMS measurement of phase-to-phase voltages• True RMS measurement of neutral current• True RMS measurement of residual voltage• Fundamental frequency active power [kW]• Fundamental frequency reactive power [kVAr]• Fundamental frequency displacement power factor cos (φ)• Power factor PF including the harmonics• Fundamental frequency active energy [kWh]• Fundamental frequency reactive energy [kvarh]• System frequency measurement11.7.3. ProtectionAll the necessary settings for the protection functions can be set via Relay SettingTool or the local HMI. The settings can be found in Main menu\Protection\.11.7.3.1. Thermal overload protectionThermal Overload Protection (3Ithdev>) constitutes a full three-phase thermaloverload protection. When applied to motor protection, the thermal unit forms anoverload protection with two time-constants, separately for both the stator and therotor.Two setting groups (basic settings and advanced settings) are available. Normally,the user sets the motor data only to the basic settings, and the relay automaticallycalculates the advanced settings.• The type of the motor to be protected is selected by means of the Device typesetting.• The Starting current setting is the ratio of the motor starting current to full loadcurrent.• The Starting time setting is the maximum permitted starting time for motor.• No of starts setting specifies how many times the motor is allowed to be startedfrom cold condition state (assuming the motor has the ambient temperature).• Cooling factor setting determines how slowly (compared to running condition)the motor cools down in case the motor is stopped. It can be defined also as aratio of cooling constant (for a stopped motor) to heating constant.A normal, totally enclosed motor cooled by a fan on therotor shaft generally has the setting of 4...6.• By means of Ambient temp. setting, the thermal protection can be given astandard temperature reference level (typically 40°C).Coolingτ Heatingτ⁄=
