Abstract
Steady state voltage problems in power
systems are those associated with undervoltages resulting
from increasing loads. Steady overvoltages can also arise
when loads served by networks are reduced, and the
problem can be exacerbated if lines supplying load centres
are long. This paper reports on a study that was conducted
to assess the impact of derating voltage of lines, by using
step down transformers on the lowest load a network can
accommodate without overvoltages. A program written in
Python and using PSS/E to perform loadflows, was used to
perform analyses at various load levels. The study showed
that with derating transformers installed, voltages in the
system were better, there was less reactive power flow, and
active power losses were lower. Derating lines using step
down transformers is therefore a potential solution for
serving low load levels.