The three-phase
system is an economical way of bulk power transmission over long
distances and for distribution. The three-phase system consists of a
three-phase voltage source connected to a three-phase load by means of
transformers and transmission lines. Two types of connections are
possible, namely delta (Δ) connection and star or wye (Y) connection.
The load and the source can be either in delta or star. The transmission
line will be in delta connection. Normally the power system is
operated in balanced three-phase condition. Most of the bulk loads such
as industrial loads are three-phase balanced loads in nature. However,
when there is a mix of single-phase and three-phase loads such as
residential loads, the load will be unbalanced. Nevertheless, an
unbalanced load can be resolved into a set of more than one balanced
system. Hence, the analysis of a balanced system at steady state will be
enough to understand three-phase system