Question

The maximum reactive power generation of a generator is limited due to:-
1. over heating of the rotor
2. stability limit of the machine
3. thermal consideration
4. both (1) & (2)

Answer 1

Correct Answer - Option 1 : over heating of the rotor

Capability curve of synchronous generator:

• The Capability Curve of a Synchronous Generator defines a boundary within which the machine can operate safely.
• For an applied shaft power, the reactive power output of a generator is limited by either field current or heating of armature winding
• Thermal capabilities impose limitations on the synchronous generator reactive power capability.
   

The limitation of operation is restricted to the following:

• The MVA loading should not exceed the generator rating, this limit is determined by the armature of the stator heating by the armature current.
• The MW loading should not exceed the rating of the prime mover.
• The field current should not be allowed to exceed a specified value determined by the heating of the field.
• For steady-state or stable operation, the load angle δ must be less than 90 degrees.