This paper is concerned with using the fault
analysis to establish the requirements for the proper selection of
circuit breaker; A Case Study of Power Holding company of
Nigeria (PHCN) 330-kV Transmission Grid System. The work is
modelled for Fault Analysis and it is written in a flexible
MATLAB programs to accommodate addition or reduction in
the Transmission Grid System. It aimed at establishing the
Circuit Breaker Capacity at any point in the system. The result is
then compared with the existing circuit breaker capacity of
PHCN 330-kV system. The short-circuit fault is simulated by
combining a solution of algebraic equations describing the
changes in the network with a numerical solution of the
differential equations. Two MATLAB programs were written
and simulated; one for Lord Flow study to know the pre-fault
bus voltages based on Gauss-Seidel Method; the other for Short
Circuit Studies which made use of Thevenin’s theorem
application. The highest Circuit Breaker Capacity established by
the result of this study is relatively lower and the investments
needed for this are smaller compared with the normal practice
with PHCN system. This reveals that PHCN system can be
protected with this low capacity circuit breaker with a reduced
cost effectiveness and equal sensitivity which is a break-through
in terms of Circuit Breaker Capacity in the field of power system
protection
