Fluke 1760, 1760TR, 434 II, 435 I, 435 II Service Guide
...
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.
Starter Disconnect
480 V
panel
000124
Power
Disconnect
factor
correction
capacitors
Adjustable
speed motor
drive
Disconnect
Application Note
Motor
Motor
Transfer
Utility
power
Ground
system
480 V
CAT IV
600 V
Main switchgear
switch
Transformer
CAT III
1000 V
Emergency
generator
UPS
From the Fluke Digital Library @ www.fluke.com/library
PDU
480 V/
277 V
panel
120 V/
202 V
panel
Servers
Lighting
Receptacle
CAT II
300 V
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.
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