Application Note

3 Fluke Corporation The costs of poor power quality
Useful kilowatts (power available)
Reactive (unusable) power
Kilowatts made unusable
by unbalance issues
Kilowatts made unusable
by harmonics
Neutral current
Total cost of wasted kilowatt hours
• Old motors, old drives, and
other motor-related issues.
• Highly distorted power, which
may cause excessive heating
in the power system.
You can avoid power fac-
tor penalties by correcting for
power factor. Generally this
involves installing correction
capacitors. But, first correct for
distortion on the system—capac-
itors can present low impedance
to harmonics and installing
inappropriate PF correction can
result in resonance or burned
out capacitors. Consult a power
quality engineer before correct-
ing PF if harmonics are present.
You can reduce peak
demand charges by manag-
ing peak loading. Unfortunately,
many people overlook a major
component of this cost—the
effect of poor power quality on
peak power usage—and thus
underestimate their overpay-
ments. To determine the real
costs of peak loading, you need
to know three things:
1. “Normal” power usage
2. “Clean power” power usage
3. Peak loading charge structure
By eliminating the power qual-
ity problems, you reduce the size
of the peak demands and the
base from which they start.
By using load management, you
control when specific equipment
operates and thus how the loads
“stack on top of each other.”
Now your building averages
515 kWh and your peak load
pegs at 650 kWh. But, you add
load management to move some
loads around and now fewer
loads stack on top of each other
at once —your new peak load
rarely goes beyond 595 kWh.
Energy costs
To reduce your power bill, you
need to record consumption
patterns and adjust the system
and load timing to reduce one or
more of the following.
1. Actual power (kWh) usage
2. Power factor penalties
3. A peak demand charge
structure
Until now, capturing the cost of
energy waste caused by power
quality issues was a task for the
most expert engineers. The cost
of waste could only be calculated
by serious number crunching,
a direct measurement of the
waste and monetization was
not possible. With the patented
algorithms used in the Fluke 430
Series II products, waste caused
by common power quality issues
such as harmonics and unbal-
ance can be measured directly.
By inputting the cost of energy
in to the instrument the cost is
directly calculated.
You can reduce power usage by
eliminating inefficiencies in your
distribution system. Inefficiency
sources include:
• High neutral currents due to
unbalanced loads and triplen
harmonics.
• Heavily loaded transformers,
especially those serving
non-linear loads.
Let’s walk through an example. Your factory/office complex aver-
ages 570 kWh of consumption during the workday, but hits peaks
of 710 kWh most days. Your utility charges you for each 10 kWh
over 600 kWh for the whole month, any time you exceed 600kWh
during a 15-minute peak measurement window. If you were to
correct for power factor, mitigate harmonics, correct for sags, and
install a load management system, you would see a different
power usage picture—one you can calculate.