A Fast Approach for Short Circuit Analysis on 330kV Nigeria Power System

Abstract

Fault in electrical power system is unavoidable. The occurrence of faults in power system
network destabilizes the system. Thus, it requires a fast technique to stabilize the system to
avoid total system collapse. In this work, an application program was developed using
MATLAB tool based on bus impedance matrix method. Bus impedance matrix is used because
it has several advantages over Thevenin equivalent method and other conventional
approaches since it can be used to analyze large network and solve for branch currents. This
approach contains off-diagonal elements of the system which Thevenin and other
conventional approaches do not have. The work investigated line-to-line fault on a 4-
bus/330kV Nigeria power system, under unbolted fault condition. The total fault current was
found to be 10p.u while the voltages for buses 1, 2, 3 and 4 were obtained as 1p.u at phase a
which shows that phase a was not affected during the fault. Phase b and phase c show equal
voltages for the respective buses during the fault. Bus-3 shows a lesser voltage of 0. 97p.u
due to fault occurring at bus 3. The approach can identify the rating of the protective device
for effective protection of the system over short circuit occurrence at a short period of about
1sec.