Figure 5.
Load distribution.
6.
PHASE BALANCE
it must carry and on the allowable
voltage drop.
Keep in mind that the
Although a generator is balanced, an
larger the wire size, the greater its
inspection of the phases at any point
capacity and the less resistance it
in the distribution system may reveal
will have, hence, less voltage drop.
that the phases are out of balance.
Economy, however, should be considered
in size determination.
Table 1 shows
In a 3 4W system, three hot wires and
the
KVA
and
current
carrying
a neutral leave the generator with the
capacities for wires ranging from a
three hot wires carrying the same
No. 8 to a 4/0.
power.
At one pole, power may be
delivered to one of the 1 2W loads in
a. Types of conductors. Conductors
the
installation
by
feeding
the
used in overhead distribution systems
facility with a branch consisting of
at Army posts are usually copper,
one phase and the neutral. Therefore,
although they may be steel, aluminum,
between this pole and the next, the
or combinations of these metals.
three phases will not be balanced.
Variations
of
this
situation
may
(1) Copper.
Copper has high
occur.
Such phase or pole to pole
conductivity and is easily spliced.
unbalances are not uncommon due to the
Hard-drawn or medium-hard-drawn copper
various loads applied to the system.
is
desirable
for
distribution
Unlike the generator balancing case,
conductors because of its strength.
this situation may be allowed to exist
Since annealing reduces the wire's
without any harmful effects to the
tensile strength from 50,000 pounds
system.
per square inch to 35,000 pounds,
soldered splices should not be used on
7.
WIRE
SIZE
AND
VOLTAGE
DROP
hard-drawn copper wire because the hot
DETERMINATION
solder anneals the joints.
Splicing
sleeves are normally used when making
The size of wire for a given section
joints.
of a system is selected on the basis
of the amount of electrical load that
2-8
Previous Page
