# Equal area criterion short note ```Lecture_11
Equal Area Criterion
Equal area criterion is one of the methods
method to analyse the stability of power
system. In this method, the
t
fault clearing time is considered as it plays
important role on transient stability.
When fault occurs in the system, in that case, if the fault is cleared much faster,
that is much very quickly,, then the system may remain stable.
Whereas, if more time
me is taken to clear the fault then the disturbance, that is the
accelerating power or decelerating
dec
power, will be remaining for a much longer
period of time. And the system become unstable under such situation.
Take an example, where a synchronous machine is connected to an infinite bus,
through a transformer and a transmission line as shown in fig, as follows.
Critical Clearing Angle
How to find Critical Clearing Angle
a. From Equal area criterion
b. From Swing equation
Case of Two Parallel Lines
a. Equal area criterion applied to the opening of one of the two lines in
parallel
b. Equal area criterion applied to Short circuit at one end of line and
disconnected at δC
c. Equal area criterion applied to Short circuit at middle of one line and
line is disconnected at δC
****
```