Utility Savings

Bill McGroarty

Suburban Electric Supply Co

What is Power Factor?

• “Power factor” involves a relationship between two types of power– working power – reactive power

Inductive Loads

• Most loads in modern electrical distribution systems are inductive: which means that they require an electromagnetic field to operate.

• Require two kinds of current:– Working power– Reactive power

Working power

• Measured in kilowatts(KW)

• Does the work for the system- providing the motion, heat or whatever else is required

Reactive Power

• Measured in kilovolt-amperes-reactive(KVAR)

• Does not do useful work

• Simply sustains the electromagnetic field

Relationship of three types of power

• Following right power triangle illustrates the relationship between these three types of power

• square of apparent power equals the square of working power plus the square of reactive power

• finally the power factor is the ratio of working power to apparent power or KW/KVA

Relationship of powerWorking power (KW)

Reactive power (KVAR)Apparent power

(KVA)

Power Factor = Working power/ Apparent power

What does power factor measure?

• Power factor measures how effectively electrical power is being used.

• A high power factor means that electrical power is being utilized effectively

• A low power factor indicates poor utilization of electrical power

• numerical eg. Paper mill operating at 100kw (working power)and the apparent power consumed was 125 KVA, you would divide 100 by 125 and come up with a power factor of 80%--represents fairly low power factor

Why should I be concerned about low power factor?

• Low power factor means that you’re not fully utilizing the electrical power you’re paying for

• In the previous example, with a power factor of 80%, your paper mill would be utilizing only 80% of the energy supplied by the utility. This means that only 80% of the incoming current is being used to produce useful work.

What can I do to improve power factor?

• The simplest way to improve power factor is to add power factor correction capacitors to your plant distribution system

• Power capacitors act as reactive current generators.

• By providing the reactive current, they reduce the total amount of current your system must draw from the utility

How much can I save by installing power capacitors?• Power capacitors provide many benefits:

– Reduced electrical utility bills ( a typical payback period is less than one year)

– Increased system capacity– Improved voltage– Reduced heat losses