Generator Capability Curve

REAL & REACTIVE POWER CONCEPTS and GENERATOR CAPABILITY CURVE - K. Arputharaju, Assistant Executive Engineer / Operation, Basin Bridge Gas Turbine Power Station, TANGEDCO, TNEB Ltd., Chennai – 600 012. 1

REQUIREMENTS OF POWER SYSTEM  It must supply energy practically everywhere the customer demands.  The load demands vary with time. The system must able to supply this ever changing demand.  The delivered energy must meet certain minimum requirements in regard to quality. The following factors determine the quality: a) The system frequency must be kept around 50Hz with a variation of ±0.05Hz. b) The magnitude of the bus voltages are maintained within prescribed limit around the normal value. Generally the voltage variation should be limited to ±5%.  The energy must be available with high reliability.  The energy must be delivered without overloading any element in the power system.  The energy must be delivered at minimum cost.

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REAL POWER (P): The real power, P is defined as the average value of P and therefore, physically, means the useful power being transmitted. Its magnitude depends very strongly on the power factor cosΦ. REACTIVE POWER (Q): The reactive power, Q is by definition equal to the peak value of that power component that travels back & forth on the line, resulting in zero average, and therefore capable of no useful work. 3

TYPE OF LOADS: TYPE OF LOAD

PHASOR

PHASE ANGLE

POWER ABSORBED BY THE LOAD P Q

I V

I

R

I

V

Ф = 0°

P>0

Q=0

Ф = +90°

P=0

Q>0

Ф = - 90°

P=0

Q