Almost to go for increased use of distributed generation

Almost in every modern civilization field, there is
the requirement of electrical energy which has resulted in a considerable
increase of electrical power consumption. To reach the large electrical energy
demand, the size of the power generating stations has become large. Now days,
in many cases, the generating stations are connected among themselves by
interconnected networks (power grids) and makes the utility systems extremely
large. Modern electrical power grids also have put forward to go for increased
use of distributed generation (DG) which is placing smaller local generation
sources closer to the loads.


Usually the consumption area of electrical power is
very wide, the chances of any kind of accident, fault or abnormal condition is
very common. In a power utility network, an short circuit is created by sudden
accidents. The sudden reduction of the impedance of the power utility network
during short circuit causes an increase in current, termed a fault current. It
is a large fault current surging through the various parts of power grids and
responsible for causing a voltage reduction too.

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The increase of electric power consumption has
necessitated an increase in the system fault current levels which has led to
larger mechanical and thermal stresses and endangers the mechanical integrity
of power system hardware viz. circuit breakers, transformers and other
equipments. The increase in load, generation, interconnection and penetration of
DG into power network rapidly increase the short circuit fault current level to
or exceeds the capacity of protective switchgear such as circuit breaker. The
short circuit fault current level in some places becomes so high that the
breaking capacity of the circuit breaker reached to its maximum possible rating
which is limited by the physics of the applied dielectric medium. Hence, the
circuit breaker must either be upgraded or replaced in the near future. Neither
up gradation nor replacement is economical and feasible from utilities
perspective as the levels of fault currents would continue to grow with the
increase in power demand. Because of these reasons the importance of limiting
the fault current has been increased considerably. With the limited fault
current, a breaker with a low rating or existing rating can be used and is cost
effective compared to the breaker replacement.