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In the system shown below, the generator was initially supplying power to the grid. A temporary LLLG bolted fault occurs at F very close to circuit breaker 1. The circuit breakers open to isolate the line. The fault self-clears. The circuit breakers reclose and restore the line. Which one of the following diagrams best indicates the rotor accelerating and decelerating areas?
Fig. (i)
Fig. (ii)
Fig. (iii)
Fig. (iv)
Given: A temporary LLLG bolted fault occurs at point F near to bus-bar 
.
Let 
: Reactance of Transmission lines
After fault occurs (when CB open the faulty line),
Initial operating point: 
on Curve 1 (under Normal conditions).
when 3-phase symmetrical fault occurs near bus-bar,
(electrical power transfer during fault) 
Operating pt. moves to 
.
to 
: Duration of fault or Time taken by 
to clear the fault
At pt. 
opens and isolate the faulty line.
Due to which operating pt. moves to pt. c on curve-2.
Then, due to accelerating power, operating pt. accelerate upto pt. 
on curve 2 .
At some pt. D, CB again closes after rectification of fault & thus curve again moves to curve 1, operating pt. E. and can swing upto pt. F maintaining stable conditions.
for stable conditions, Accelerating Area 
decelerating Area 
Hence, option (b) is correct.