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.
The costs of poor
power quality
The interdependence of various
systems adds layers of
complexity to this issue. 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
Utility
power
Ground
system
Main switchgear
UPS
panel
drive
Transfer
switch
480 V/
277 V
panel
120 V/
202 V
panel
Lighting
Transformer
Emergency
generator
Receptacle
000124
swit
PDU
480 V
Starter
Disconnect
Power
factor
correction
capacitors
Adjustable
speed motor
000124
CAT II
300 V
CAT III
1000 V
CAT IV
600 V
F r o m t h e F l u k e D i g i t a l L i b r a r y @ w w w. f l u k e . c o m / l i b r a r y
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.
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
grounding, 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.
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?
Measuring power
quality costs
Power quality problems make
their effects felt in three general
areas: downtime, equipment
problems, and energy costs.
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.
2 Fluke Corporation The costs of poor power quality
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.
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.
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 managing 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 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.
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?
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.
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
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.
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 drops to
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.
Saving PQ dollars
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.
3 Fluke Corporation The costs of poor power quality
• 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.
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.
The costs of poor
power quality
The interdependence of various
systems adds layers of
complexity to this issue. 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
Utility
power
Ground
system
Main switchgear
UPS
panel
drive
Transfer
switch
480 V/
277 V
panel
120 V/
202 V
panel
Lighting
Transformer
Emergency
generator
Receptacle
000124
swit
PDU
480 V
Starter
Disconnect
Power
factor
correction
capacitors
Adjustable
speed motor
000124
CAT II
300 V
CAT III
1000 V
CAT IV
600 V
F r o m t h e F l u k e D i g i t a l L i b r a r y @ w w w. f l u k e . c o m / l i b r a r y
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.
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
grounding, 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.
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?
Measuring power
quality costs
Power quality problems make
their effects felt in three general
areas: downtime, equipment
problems, and energy costs.
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.
2 Fluke Corporation The costs of poor power quality
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.
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.
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 managing 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 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.
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?
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.
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
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.
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 drops to
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.
Saving PQ dollars
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.
3 Fluke Corporation The costs of poor power quality
• 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.
BCD Electric RSS feed