The costs of poor
power quality
Productivity is the key to survival in today’s globally competitive environment. When
you think about the basic inputs to production—time, labor, and materials—you can
see there isn’t much room for optimization. You have 24 hours per day, labor is costly,
and you don’t have much choice in materials. Thus, every company must use automation to gain more output from the same inputs, or perish.
So, we rely on automation, which in turn relies on clean power. Power quality
problems can cause processes and equipment to malfunction or shut down. And the
consequences can range from excessive energy costs to complete work stoppage.
Obviously, power quality is critical.
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The interdependence of various
systems adds layers of complexity to power quality issues.
Your computers are fine, but the
network is down so nobody can
book a flight or file an expense
report. The process is operating correctly, but the HVAC has
shut down and production must
stop. Mission-critical systems
exist throughout the facility and
throughout the enterprise—power
quality problems can bring any
one of these to a grinding halt at
any time. And that will usually
be the worst possible time.
Where do power quality problems come from? Most originate
inside the facility. They may be
due to problems with:
• Installation—improper ground-
ing, improper routing, or
undersized distribution.
• Operation—equipment
operated outside of design
parameters.
• Mitigation—improper
shielding or lack of power
factor correction.
• Maintenance—deteriorated
cable insulation or grounding
connections.
Even perfectly installed and
maintained equipment in a
perfectly designed facility can
introduce power quality problems as it ages.
The direct measurement of
wastes due to poor power quality can be achieved with the
Fluke 430 Series II instruments,
which directly measure waste
due to harmonics and unbalance,
and quantify the cost of that
waste based on the unit cost of
power from the utility.
Power quality problems can
also originate from outside the
facility. We live with the threat
of unpredictable outages, voltage sags, and power surges.
Obviously, there’s a cost here.
How do you quantify it?
Let’s walk through an example. Your factory makes 1,000
widgets per hour, and each widget produces $9 of revenue. Thus,
your revenue per hour is $9,000. If your costs of production are
$3,000 per hour, your operating income is $6,000 per hour when
production is running. When production is down, you lose $6,000
per hour of income and you still have to pay your fixed costs
(e.g., overhead and wages). That’s what it costs to be down. But,
downtime has other costs associated with it:
• Scrap. How much raw material or work in process do you have
to throw away if a process goes down?
• Restart. How much does it cost to clean up and restart after an
unplanned shutdown?
• Additional labor. Do you need to pay overtime or outsource
work to respond to a downtime incident?
Downtime
To quantify system downtime
costs, you need to know two
things:
1. The revenue per hour your
system produces.
2. The costs of production.
Also, consider the business
process. Is it a continuous, fully
utilized process (e.g., a refinery)?
Must your product be consumed
when produced (e.g., a power
plant)? Can customers instantly
switch to an alternative if the
product is not available (e.g., a
credit card)? If the answer to any
of these questions is yes, then
lost revenue is difficult or impossible to recover.
Are you an OEM producer? If
you can’t make timely deliveries,
your customer may switch to a
source that can.
Equipment problems
Exact costs are hard to quantify,
because you are dealing with
many variables. Did that motor
really fail from excess harmonics, or was there some other
cause? Is Line Three producing
scrap because variations in the
power supply are causing variations in machine performance?
To get the correct answers, you
need to do two things:
1. Troubleshoot to the root
cause.
2. Determine the actual costs.
Measuring power
quality costs
Power quality problems make
their effects felt in three general
areas: downtime, equipment
problems, and energy costs.
2 Fluke Corporation The costs of poor power quality
Here’s an example. Your factory is making plastic webbing that
must be of uniform thickness. Operators consistently report high
scrap rates in the late afternoon. You can directly trace machine
speed variances to low voltage caused by heavy HVAC loads. The
operations manager calculates the net scrap costs are $3,000 per
day. That’s the revenue cost of your low voltage. But, don’t forget
other costs, such as those we identified for downtime.
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
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 unbalance 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.
• 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 factor penalties by correcting for
power factor. Generally this
involves installing correction
capacitors. But, first correct for
distortion on the system—capacitors 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 correcting 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
underestimate their overpayments. 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 quality 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.
effect of poor power quality on
peak power usage—and thus
Let’s walk through an example. Your factory/office complex averages 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 600kWh
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.
3 Fluke Corporation The costs of poor power quality
Saving money with PQ
You’ve tallied up the costs of
poor power quality. Now, you
need to know how to eliminate
those costs. The following steps
will get you there.
• Examine design. Determine
how your system can best
support your processes and
what infrastructure you need
to prevent failure. Verify
circuit capacity before installing new equipment.
Re-check critical equipment
after configuration changes.
• Comply with standards.
For example, examine your
grounding system for compliance with IEEE-142. Examine
your power distribution
system for compliance with
IEEE-141.
• Examine power protection.
This includes lightning
protection, TVSS, and surge
suppression. Are these properly specified and installed?
• Get baseline test data on all
loads. This is the key to
predictive maintenance, and
it allows you to spot emerging
problems.
• Question mitigation.
Mitigating power quality problems includes correction (e.g.,
grounding repair) and coping
(e.g., K-rated transformers).
Consider power conditioning
and backup power.
• Review maintenance
practices. Are you testing,
then following up with
corrective actions? Conduct
periodic surveys at critical
points—for example, check
neutral to ground voltage and
ground current on feeders
and critical branch circuits.
Conduct infrared surveys
of distribution equipment.
Determine root causes of
failures, so you know how to
prevent recurrences.
• Use monitoring. Can you see
voltage distortions before they
overheat motors? Can you track
transients? If you don’t have
power monitoring installed, you
probably won’t see a problem
coming—but you will see the
downtime it causes.
At this point, you need to determine the costs of prevention and
remediation—and then compare
those to the costs of poor power
quality. This comparison will
allow you to justify the investment needed to fix the power
quality problems. Because this
should be an ongoing effort, use
the right tools so you can do
your own power quality testing
and monitoring rather than
outsourcing it. Today, it’s surprisingly affordable—and it will
always cost less than downtime.
Fluke. Keeping your world
up and running.
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4 Fluke Corporation The costs of poor power quality
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