Synchronous Motor Applications

The 869 is equipped to protect and control synchronous machines

without the need for external hardware. All protection functions essential

to the synchronous motor during asynchronous operation while starting

up, during normal and overload operations and under fault conditions

are available. In addition to stator  protection and control, the relay

provides protection and monitoring of exciting rotor during pull-out or

loss of synchronism condition with elements like Out-of-Step, Loss-of

Field, Reactive Power, and Power Factor. With its well established and

matured Thermal Model, it prevents overheating of both stator and rotor

windings during both synchronous and asynchronous operation. During

asynchronous operation or startup, the thermal model with VD (voltage

dependent) function provides protection against excessive heating in the

damper winding due to stalled or locked rotor conditions.