This project presents a methodological approach, suggestions and information
in uprating the existing 275kV transmission overhead line. The work also calculate
and analyses the effect of conductor swing angle on L3 tower top geometrics and keep
the probability of flashover at low state. In this project, the insulator length and
clearances of swing conductor to tower body, top cross-arm, bottom cross-arm and
conductor to conductor are considered. The purpose of this work is to determine the
clearances necessary to insulator withstand for 400kV line. In addition, it is also
important to make sure that conductors have to maintain the clearances under TOV
(temporary over-voltage), switching and lightning overvoltages. The work in this
project have used Excel and Smart Draw to analyze the results and plot the clearance
distances of swing conductor, also the phase to phase rms voltage and redrawing the
existing overhead tower. Therefore, voltages rating for the L3 tower can be
determined through the available clearances. Firstly, the voltage rating is determined
with standard 400kV specification of insulator length. Then, the insulator is being
shorted to do the analysis to the voltage rating and lastly, the overall cross-arm is
changed to fully insulate such as composite cross-arm. As the result, by using standard
insulator length, the tower only carried 351kV rather than composite cross-arm that
carry 450kV. The standard L3 tower will be increase the power transfer capacity to
400kV in term of voltage by changing the steel cross-arm to composite cross-arm
