power distribution - Siemens

13Medium Voltage EquipmentMV Controllers (MVC) up to 7.2 kVMotor Protection OptionsDrive motors often play a decisive role inthe functioning of a production process.Motor damage and breakdowns notinfrequently lead also to consequentialdamage and production shutdowns, thecost of which significantly exceeds thecost of repairing the motor. Optimumdesign of the motor protection ensuresthat damage following thermal overloadis prevented, meaning that there is noreduction to the normal service life.Secondary faults are minimized in theevent of short circuits, ground faults andwinding faults. The spectrum extendsfrom small low-voltage motors with anoutput of a few kW to high voltagemotors with outputs measured in MW.Protection system design must be basedon the rating of the motor, theimportance of the drive for thetechnological process, the operatingconditions and the requirements of themotor manufacturer.Common motor protection functions andSIPROTEC motor protective relayselection tables are provided below.Protective RelayingSWITCHGEARProtection functions for various types of motor faultsFault Protection ANSI NumberStator thermal overload Stator thermal overload protection 49Rotor thermal overload during start2 Protection principles for the rotor overload protectiontoo long or blocked Motor starting time supervision 48too frequent Restart inhibit 66, 49RGround-fault Ground-fault protection (I 0 >;U 0 >; 10 MW7UM627UM61+ differential protection + (Option: Generator Basic)+ control functions 7UM62+ high accuracy (Option: Generator Basic)+ high sensitivity or with control functions via bay mimic diagram in graphic display+ operating range in a wide 7SJ64frequency band (11Hz - 68Hz)+ (Option: Generator Basic)For more information, please visit http://automation.usa.siemens.com/consultant/ or contact your local sales office.13-22Siemens Power Distribution & Control, SPEEDFAX 2007-2008 Product Catalog