Training Manual on Energy Efficiency - APO Asian Productivity ...

Figure 5-5 Maximizing capacity
The vector sum of the active power and reactive power make up the total
(or apparent) power used. This is the power to be supplied by the utility for
meeting all active and reactive power needs of users and utility electrical
generation and distribution systems are designed accordingly.
Since it is only the active power or kilowatts that are of real use, there is
an advantage in operating with a power factor close to unity—that is, drawing
close to zero reactive power from the utility. In this way, the capacity of a
utility electrical network can be optimally used, with minimum losses. In fact,
the utilities penalize users for low power factors and sometimes incentivize
high power factors at the user end, in their tariff structures. Installing and
maintaining capacitors helps industry to balance the reactive power of
inductive loads and to improve power factors at the user end, which also offers
benefits of better voltage, reduced maximum demand, and lower distribution
losses within the industry premises.
Capacitor locations:
For motors of 50 hp and above, it is best to install power factor correction
capacitors at the motor terminals since distribution circuit loading is reduced.
Figure 5-6 shows capacitor banks connected at the bus for each motor control
centre. This compromise to Method 1 will reduce installation costs. The least
expensive method shows capacitor banks connected at the service entrance.
However, the disadvantage is that higher feeder currents still flow from the
service entrance to the end-of-line equipment and will only benefit the utility in
a real sense.
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Electrical Load Management