Now, suppose, that a self clearing transient three phase short circuit fault occurs on the line. During the fault, the electrical output power drops to zero. The resulting rotor acceleration advances rotor angle to . After a time interval , corresponding to angle , the fault is cleared and the operating point jumps back to the sinusoidal curve. As per equal area criteria, the rotor will swing up to maximum rotor angle , such that,
Accelerating Area (A₁) = Decelerating Area (A₂)
Rotor angle corresponding to fault clearing time can be computed by swing equation,

where H is the equivalent rotor angle inertia.
During fault, P_e = 0, hence,

On integrating both the sides with respect to variable t,

Recall that prior to fault, is a stationary point. Hence, the initial condition of is specified as follows: