Introduction
The demand of power is increasing with each passing day which
requires more resources of generation and construction of new
grids. The developing countries that do not have sufficient
resources have to perform load shedding in order to achieve ‘power
system stability’. When the load increases, the generators connected
to a power system start slowing down that in turn results
in reduced electrical frequency. The minimum threshold value
for frequency in Pakistan is 49.5 Hz. When frequency decreases
below its threshold value due to a sudden increase in load or
tripping of major power plants (or transmission lines), the whole
system becomes vulnerable to losing its stability. The tripping of
one major generator (or power plant) or a transmission line results
in the re-distribution of load on other generators or transmission
lines and if they are not able to bear this increased load (particularly
in case when they already are operating near their rated
capacities), the whole system could collapse. This condition is
known as cascaded failure or blackout [1].
The cascaded failures are a major threat to power systems. They
should not be allowed to happen as they can prove detrimental to