Correct Answer - Option 1 : 60

__Concept:__

Speed of synchronous generator in rpm is given by

\({N_s} = \frac{{120f}}{P}\;\)

Where,

f = supply frequency in Hz

P = Number of poles

Calculation:

Given-

Ns = 100 r/min = 100 rpm,

f = 50 Hz

When hydraulic turbine is connected to synchronous generator, then both are running at same speed

∴ \(100 = \frac{{120 \times 50}}{P}\)

P = 60