Question

A synchronous generator is connected to infinite bus through a loss-less line and a circuit breaker. The generator is delivering 1.0 p.u. power to infinite bus. The time of operation of CB is 0.1 sec. If the mechanical input to synchronous generator is suddenly increased to double, the time of operation of CB should be

• A. 0.1 second
• B. more than 0.1 second but less than 0.2 seconds
• C. does not depend on mechanical input
• D. less than 0.1 second

Answer 1

The correct option is D less than 0.1 second

The maximum time of operation of CB is $t_c$ second,

$t_c=Criticaltime$

$t_c=\sqrt{\frac{2H({\delta }_{cr}-{\delta }_0)}{\pi f.P_s}}$

$t_c\propto \frac{1}{\sqrt{P}}$

If $P\uparrow ,\to t_c\downarrow sotimeofoperationofCBshouldbelessthan0.1second$