Download ElEctric and MagnEtic FiElds (EMF)

Electric and Magnetic Fields (EMF)
Answers to frequently asked
questions for Xcel Energy customers
EMF in nature
Electric and magnetic fields
Long before humans figured out
how to capture electricity for
everyday use, electric and
magnetic fields (EMF) were natural
phenomena. We can see that a
compass needle is affected by the
earth’s natural magnetic field – and
it is a stronger field than those found
around most household appliances
and electric power lines.
Electric and magnetic fields are created by the electricity we need to run the
appliances and lights in our homes. EMF is present around electric power
lines as well.
The difference between natural
EMF and human-made EMF is
natural fields are static – they don’t
alternate back and forth – while
the electricity we use is alternating
current. It operates at a frequency of
60-Hertz, meaning electric charges
move back and forth 60 times every
second and therefore is referred to
as alternating current.
Electrical substations serve many functions in controlling and transferring
power on an electrical system. Several different types of equipment might be
present, depending on the functions of the particular substation. For example,
transformers change the high voltages used by transmission lines to the
lower voltages used by distribution lines. Circuit breakers are used to turn
power lines on and off.
There are two basic types of power lines: transmission lines and distribution
lines. Transmission lines are high-voltage power lines. The high voltage
allows electric power to be carried efficiently over long distances from
electrical generation facilities to substations. In the United states, most
transmission lines use alternating current (ac) and operate at voltages
between 50 and 765 kV (1 kV or kilovolt = 1000 volts (V)).
Utilities use lower-voltage distribution lines to bring power from
substations to businesses and homes. Distribution lines operate at voltages
at or below 35 kV. For residential customers, these levels are further reduced
to 120/240 V once the power reaches your home.
Transmission lines
(50–765 kV)
Transmission station
Steam electric
generating plant
Distribution station
Distribution lines
(4–44 kV)
EMF | Xcel Energy | 2
Wherever there’s electricity…
…There are electric and magnetic fields (EMF).
Electric and magnetic fields are invisible–just like radio or TV signals. They surround any wire that is conducting
electricity. The distribution power line serving your neighborhood produces EMF. So do household appliances such as
your toaster, hair dryer, lamps and washing machine. Business equipment, such as computers, copiers and fluorescent
lights, produce EMF, too.
Typical 60 Hz magnetic field levels from some common home appliances
Magnetic field 6 inches from appliance (mG)
Magnetic field 2 feet away (mG)
Electric shaver
100
—
Vacuum cleaner
300
10
Electric oven
9
—
Dishwasher
20
4
Microwave oven
200
10
Hair dryer
300
—
Computers
14
2
Fluorescent lights
40
2
Faxogram machines
6
—
Copy machines
90
7
Garbage disposals
80
2
Source: National Institute of Environmental Health Services / National Institutes of Health: EMF Associated with the Use of Electric Power
For more information, call the EMF answer-line, (612) 330-6548 or Customer Service at 1(800) 895-4999.
EMF | Xcel Energy | 3
Wherever there’s elecricity… (continued)
Electric fields
An electric field is created by voltage.
The higher the voltage, the greater
the electric field. For example, a
high-voltage transmission line that
brings electricity to a city will create
a much stronger electric field than
a television set or electric range.
Electric field strength is measured
in volts per meter (V/m) or kilovolts
per meter (kV/m).
An electric field is different from
a magnetic field. An electric field
is created whenever an electrical
appliance is plugged in–even
when it’s turned off.
Magnetic fields
When you turn on an electric
appliance, the electric current
creates a magnetic field. The higher
the current, the greater the magnetic
field. If you use a hair dryer on
the low setting, for example, the
magnetic field will be less than when
you use the high setting. Magnetic
field measurement is expressed in
units called Gauss (G) or milliGauss
(mG). A milliGauss is one-thousandth
of a Gauss. In a home, the
background magnetic field might be
0.5 to 4.0 mG, while a measurement
directly under a transmission line or
near an operating appliance might be
20 to 200 mG.
Turn on an electrical appliance
and you make a magnetic field
around the appliance.
EMF | Xcel Energy | 4
Properties of electric and magnetic fields
Ability to pass through objects
Most objects, such as a wall or even a tree, block electric fields. Unlike
electric fields, magnetic fields cannot easily be shielded, and therefore
will penetrate structures.
Intensity over distance
Both electric and magnetic fields are strongest close to their source.
For example, if you move a few feet away from an operating toaster,
the magnetic field reaching your body will be substantially less.
Exposure to magnetic fields decreases with distance
Suppose you’re standing in your kitchen, waiting for a cup of coffee to heat in
the microwave. Out of your window, you can see two Xcel Energy employees
working on a large distribution power line.
What’s your exposure to the magnetic field around the distribution
line and to the magnetic field around your microwave? Read on.
• The worker up near the line is in a magnetic field of about 50 milliGauss
(mG), the worker below the line is in a magnetic field of about 4 mG;
while you–80 feet away–are in a magnetic field of approximately 1 mG
from the power line.
• If you were standing 1 foot in front of your microwave, your exposure
from your microwave alone would be about 60 mG. Move another
couple feet away and the magnetic field from your microwave would
be approximately 4 mG.
Changes with time
Since Xcel Energy carefully regulates the voltage at which we generate
power, electric fields around power lines and household appliances will be
quite constant throughout the day or year, whether power is being conducted
or not. Unlike the constant electric fields, magnetic fields vary with the
amount of current being drawn. For example, when you come home from
work or school and turn on the electric range or other electrical appliances,
the current flowing in your home increases, as do the magnetic fields. The
strength of these fields is determined by current flow and how close you are
to the source.
EMF | Xcel Energy | 5
Useful terms about electricity and EMF
Current: The movement or flow of electricity. Current is measured in amperes or amps.
Distribution lines: Power lines carrying power to neighborhoods (primary distribution) and to one or several buildings
(secondary distribution). These typically operate at 35 kV (35,000 volts) or less.
Electric fields: An electric field is created by voltage. An electric field is created whenever an electrical appliance is
plugged in–even when it’s turned off. The higher the voltage the greater the electric field.
Epidemiology: The science of occurrence of diseases in human populations, with the purpose of identifying cause
and effect. Much of EMF research is epidemiological research.
Magnetic fields: When you turn on an electric appliance, the electric current creates a magnetic field. The higher the
current, the greater the magnetic field.
Neutrals: A grounded conductor that completes the electrical loop allowing current to flow back to the source.
Because the neutral conductor is grounded, the earth will provide a parallel path for this neutral return current.
Power frequency fields: These are low-frequency fields (50–60 Hz) with low energy levels, generated by power lines
and wiring in buildings and appliances.
Right-of-way (ROW): An area of land around a power line that a utility has acquired for the construction and operation
of the line.
Service: Point of connection between the electric utility and the customer’s electrical system.
Service drop: The overhead or underground cable that brings power to a residence or business from the distribution
line; it usually attaches to the eave of the building if overhead.
Transmission line: A power line carrying high-voltage electricity between regions. Transmission lines are built on
steel towers, steel poles and wood poles, and operate at voltages between 50 and 765 kilovolts.
Underground (UG): Refers to electrical conductors and equipment located below ground surface.
Voltage: The measurement of the electric force required to move an electric charge. Voltage is measured in volts.
1,000 volts = 1 kilovolt (kV)
Volts-per-meter: Measurement for electric fields. 1,000 volts-per-meter = 1 kV/m
Wire codes: Classifications of electrical wiring configurations of power lines near residences. Introduced as a
surrogate measure to estimate long-term magnetic field exposure.
EMF | Xcel Energy | 6
Can EMF be harmful? Past and present research
Several studies and statements
from expert agencies and work
groups have indicated that exposure
to EMF is not linked to particular
health outcomes. After 30 years
of research there is no conclusive
evidence of harmful effects.
In order to analyze the possibility that
any exposure to EMF could present
a health risk for humans, scientists
have conducted numerous national
research programs and many more
are in progress. This research takes
several forms.
• Laboratory studies in which single
cells or cell groups are exposed to
EMF under a variety of controlled
conditions.
• Laboratory studies in which
animals (such as rats and mice)
are exposed to EMF in controlled
conditions and any possible
effects are analyzed.
• Studies of human populations in
various communities, attempting
either to prove or disprove that
EMF and various diseases have
any linkage.
• Studies in occupational settings,
attempting to investigate
workplace exposure to EMF
and any effects these fields
might have on the development
of various diseases.
When examining the issue of
EMF exposure and health risks, it
is necessary to consider all relevant
evidence, including studies reporting
no effect of the exposure, with
due attention to the relevance and
quality of the study. All four study
types (epidemiology, animal testing,
cellular, occupational) are subject to
many different sources of error, and
independent replication is needed
in different laboratories (or human
populations) before results can be
considered established.
Early research in the 1960s
concentrated on possible health
effects from electric fields. Electric
fields have received less attention,
partly because they are readily
shielded by building materials, so
that fields from overhead power
lines are very much weaker inside
a building than outside. By the early
1970s, most scientists had concluded
electric fields do not pose a threat to
human health, so study shifted away
from electric fields.
Since the late 1970s, the possible
health effects of magnetic fields
have been the subject of public
interest and significant study. The
most recent scientific research and
comprehensive review by federal
agencies and scientific organizations
concluded the evidence for a risk
of cancer and other human disease
from exposure to magnetic fields
is “weak.”
EMF | Xcel Energy | 7
Research on the
possible health effects
of EMF continues
While no one can state that
exposure to any substance or
agent is absolutely safe, research
can establish that a substance is
unsafe. The interaction of humans
with EMF is complicated and
continues to be an area of
public concern.
Research continues in areas that
scientists believe warrant fundamental
study, including leukemia, breast
cancer, neurodegenerative and
cardiovascular diseases, and
methodological modeling of
biophysical processes. Other research
programs are investigating the
implementation of new technologies
that lower EMF exposure.
Our commitment to you
You can count on Xcel Energy to be a
reliable, well-informed EMF resource.
If you have questions about EMF:
• Call the EMF answer-line,
612-330-6548, or customer
service at 1-800-895-4999;
• Or visit our website:
xcelenergy.com Go to
Safety & Education>
At Home & Work>
Electric Safety
Living with EMF
A few simple steps you can take to
help reduce your exposure to EMF
Experts are telling consumers that EMF exposure is probably not a health
hazard. However, if you are interested in reducing your exposure, follow
these simple tips:
• Move bedside motor-driven electric clocks or other electrical devices
away from your bed.
• Stand away from an operating microwave oven or other appliances
that use a lot of electricity.
• Remind family members to sit a few feet away from the TV and
at least arm’s length away from the computer screen.
• Tell your children not to play around electric equipment.
(This is important for safety reasons, too!)
Remember: to conserve energy, turn off lights and other appliances
when you’re not using them. When you turn them off, you’re lowering
your family’s magnetic field exposure as well. It is also important to
properly maintain your appliances.
Prudent avoidance:
The philosophy advocated by some until further EMF research results are
known. Under this philosophy, those EMF exposures that can be avoided–
without major investments–are avoided.
Appliance Magnetic Fields
Magnetic field measurements can vary by electrical device and the
number of devices and in use.
For more information, call the EMF answer-line, 612-330-6548 or
customer service at 1-800-895-4999.
EMF | Xcel Energy | 8
EMF vs. Stray Voltage
Two different issues
Stray voltage shouldn’t be confused
with electric and magnetic fields
(EMF). These are two different
concepts.
Stray voltage is low-level voltage–
usually less than 5 volts–on a metal
object. In a dairy barn, for example,
where the metal objects are tied
to the barn’s electrical grounding
system. Humans generally do not
notice the stray voltage, but some
farm animals–especially dairy
cows–are more sensitive.
Stray voltage is not a mystery. It
has been studied for years and
much is known about this
phenomenon. Research on the
problem has resulted in a number
of techniques to reduce stray
voltage to acceptable levels.
Electric and magnetic fields are a
separate issue. They exist around
anything that is conducting electricity,
including the appliances and wiring
in your home and office and the
power lines that run down the street.
Scientists generally agree that the
electric fields we encounter daily do
not cause any adverse health effects.
EMF | Xcel Energy | 9
The most recent scientific research
and comprehensive review by federal
agencies and scientific organizations
concluded that the evidence for a risk
of cancer and other human disease
from the magnetic fields is “weak.”
Answers to some frequently-asked questions about EMF
Q Why can’t someone figure
out a way to get rid of EMF?
Q Are there state or federal
standards for EMF exposure?
Q What do EMF measurements
tell me?
AThere is no known way to get
rid of EMF. Electric and magnetic
fields occur wherever there
is electric power. The same
electricity that powers the lights
and appliances in your home,
office or school creates these
electric and magnetic fields.
A There are no federal standards
limiting residential EMF exposure
from transmission lines, but
there are federal occupational
standards that apply in the
work place. The EMF levels of
appliances vary by manufacturer
and model. The designs of
many newer model appliances,
in general, often produce lower
fields than older models. There is
no federal certification program
on EMF levels so beware of
advertisements on appliances
making claims of federal
government certification of
low or no EMF levels.
A Magnetic field measurements
are directly related to the amount
of current flowing through
transmission or distribution lines
or appliances. Current is linked
to the amount of electricity
you are using and the specific
way your house or business is
wired. The amount of current
on Xcel Energy’s power lines is
determined by the amount of
electricity being used by
our customers.
It is the nature of electricity to
create EMF: If we use electricity,
EMF will result.
Q What level of EMF exposure
is safe?
AThere is no number we can point
to that is a safe or dangerous level
of EMF exposure. We don’t know
if certain levels of EMFs are safer
or less safe than other exposures.
We also do not know if continuous
exposure to a given field intensity
causes a biological effect, or if
rapid changes in exposures
cause effects.
Xcel Energy relies on state and
federal health agencies to identify
hazardous substances or physical
agents with adverse health
effects. These experts evaluate
health research to determine if
exposure limits are necessary.
The accumulated evidence of
health research on EMF falls
short of establishing whether
magnetic fields cause adverse
health effects.
Q Will underground lines
reduce EMF?
A Placing power lines underground
does not shield magnetic fields.
Magnetic fields are difficult to
block and will continue to pass
through the ground. At the center
of an underground transmission
line, fields from a buried line can
actually be higher than those
from an overhead line. These
EMF levels will drop off quickly as
distance increases. Underground
lines also present challenges
during outages. Faults occurring
in underground installations are
typically more difficult to locate
and repair. Repair difficulty and
duration are significantly greater
than required to repair overhead
power lines.
EMF | Xc el En ergy | 10
Fairly simple measurements
can be taken of main sources
of elevated magnetic fields
inside or outside a home. The
measurements taken at your
home or business are a
“snapshot” of what magnetic
field levels are. EMF levels will
vary based on the time of day,
time of year, number and type
of appliances or office equipment
in use. Your measurements are
also directly related to how close
our inspectors are to the source
of the field.
Questions & Answers (continued)
Q What is the metal electrical box
on the corner of my lot? And is
it a source of EMF?
QShould I be concerned if
I live near a power line or
substation?
AIf the electric distribution lines in
a neighborhood are underground,
the box is probably a surface
(pad-mounted) transformer.
Transformers are electrical devices
used to increase or decrease the
voltage in the electrical power
system for best efficiency during
transmission, distribution, and
use. Each transformer provides
electrical service to several
different residences (typically
four to eight) in a neighborhood.
AAfter more than 30 years of
intensive research on power
lines and EMF by our country’s
most prestigious government
research organizations, there is no
evidence of health effects from
power lines or exposure to EMF
– even at high levels. These fields
decrease as distance from the
source increases. For high voltage
transmission lines, EMF fields
generated by these power lines
are negligible and at “background”
levels at distances greater than
300 feet.
Very little magnetic field comes
from a transformer and its
connecting lines, and it will
decrease rapidly with distance.
Q Does EMF come from a
transformer?
AThe only connection between
the high voltage and low voltage
side of a transformer is through
a magnetic field in the iron core
within the transformer. The iron
is very good at confining the
magnetic field, so very little
magnetic field gets out of a
transformer. EMF will be present
near the transformer and its
connecting lines. Transformer
fields are localized and will
decrease rapidly with distance.
QHas Xcel Energy developed any
recommendations regarding
the distance that schools
should be located from power
lines?
A Xcel Energy transmission lines
are constructed in compliance
with the National Electric Safety
Code. We have no additional
recommendations beyond these
requirements.
Q Will EMF exposure interfere
with the operation of
pacemakers?
A Under certain circumstances,
EMF can interfere with
cardiac pacemakers.
For this reason, the American
Conference of Governmental
Industrial Hygienists (ACGIH) has
issued EMF exposure guidelines
for workers with pacemakers.
Depending on the pacemaker
manufacturer and design, the
E M F | X c e l E n e r g y | 11
magnetic field threshold for
interference is in the range of
2 to 12 Gauss. Check with your
pacemaker manufacturer if you
have a concern.
QI have heard of instances
where there are an unusual
number of health cases around
electrical facilities. Are the
facilities and EMF causing
these health events?
A Most clusters of health events
are reported to public health
agencies by concerned citizens.
And according to the Centers
for Disease Control, most
investigations of suspected
clusters fail to demonstrate
that an excess of disease cases
actually exists. Investigations of
clustered health cases like this
have indicated that most disease
patterns occur merely by chance.
If you are concerned about an
unusual aggregation of health
events, contact your local
health department.
For more information
about EMF
• Call Xcel Energy’s EMF
answer-line, 612-330-6548,
or customer service,
1-800-895-4999:
• Or visit our website:
xcelenergy.com Go to
Safety & Education>
At Home & Work>
Electric Safety
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Northern States Power Company-Minnesota, Northern States Power Company-Wisconsin, Public Service Company of Colorado and Southwestern Public Service Company, Xcel Energy Companies. | 12-07-037
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