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 computed at different load levels. A graph for the conductors is drawn as a comparison,
indicating the most economical conductor size required for each particular load level.
8.4.7 Power Factor Correction. Power factor is defined as the rate of useful working current
to total current in the line. Since power is the product of current and voltage, power factor can
also be defined as the ratio of real power to apparent power. This ratio is expressed as:
kW
Power Factor
=
kVA
Where:
kW = real power
kVA = apparent power
It is advantageous to have the power factor near unity. If the power factor is below 90 percent, a
penalty is imposed by most utilities or power suppliers. Under these circumstances, the energy
losses are too high. In order to correct the situation, capacitors are installed on-line at strategic
locations.
The advantages of installing capacitors are:
(a) Improvement in power factor.
(b) Reduction of energy losses.
(c) Rise in voltage.
(d) Service reliability.
(e) Avoidance of expensive line conversion cost.
The power factor correction study can be best performed in conjunction with the voltage drop
study. The capacitor placements can be performed by checking the power factor value or the
kVAR losses on the circuit resulting from the load it is carrying. Installing the capacitors and
improving the power factor to near unity will reduce the kVAR losses and raise the voltage,
thereby reducing the voltage drop on the circuit.
8-27
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