Question

An alternator operating at 50 Hz is delivering 40 MW power to a system. Due to increase in load, generation was increased by 5 MW using droop control with frequency value dropping by 0.50% of rated value. As load further increases, the frequency of operation becomes 49.20 Hz and hence the power supplied by alternator at this frequency will be

• A. 47 MW
• B. 56 MW
• C. 52 MW
• D. 50 MW

Answer 1

The correct option is B 56 MW

Assuming full load frequency to be 50 Hz
By extra loading of 5 MW, frequency drop by 0.5%

i.e., $\frac{0.5\times 50}{100}=0.25Hz$

$\therefore$New frequency $=50-0.25=49.75Hz$


$tan\theta =\frac{50-49.75}{45-40}=\frac{49.75-49.20}{x-45}$

$\frac{0.25}{5}=\frac{0.55}{x-45}$

$x-45=11$

$x=11+45=56MW$