Brochure
Electric and Magnetic Fields
TransGrid operates and maintains the high voltage electricity transmission network in NSW, ACT and
other areas of the National Electricity Market, connecting generators to distributors and major end users.
Our core role is to provide safe, reliable and efficient transmission services to NSW and the ACT. We also provide similar
services to other areas of the National Electricity Market.
This brochure is designed to provide general information on electric and magnetic fields, commonly referred to as ‘EMFs’
which are associated with, but are not unique to, TransGrid’s transmission lines and underground cables.
The electricity supply chain
Most of the state’s electricity is generated at large coal, gas, hydro and wind power stations, and is then transmitted by
our network through high voltage transmission lines and underground cables. Electricity distributors such as Ausgrid,
Essential Energy, Endeavour Energy and ActewAGL then deliver electricity to more than 3 million homes, factories and
businesses to keep you connected.
What are Electric and Magnetic Fields?
Electric and magnetic fields are fundamental phenomena which play an essential role in making electrical equipment and
appliances work. Their existence has been recognised since electricity was discovered.
Electric Fields
An electric field is an area where electric charges experience a force. The strength of this force is related to the voltage
of the source of the field. The higher the voltage the stronger the electric field. Electric fields are strongest closest to the
wires and their level reduces quickly with distance. Most materials (including brickwork, metal and human skin) act as a
shield or barrier to electric fields. The level of electric fields is measured in thousands of volts per metre (kV/m).
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Electric and Magnetic Fields
Magnetic Fields
A magnetic field is an area where magnetic materials experience a force. Magnetic fields are produced by the flow of an
electric current through a wire. The higher the current, the greater the magnetic field. The strength of magnetic fields is
measured in milliGauss (mG). Like electric fields, magnetic fields are highest closest to the wire and their level reduces
quickly with distance. However, most materials will not act as a shield or barrier to magnetic fields.
Electric and Magnetic Fields (EMF) versus Electromagnetic Radiation (EMR)
It is not uncommon for EMF to be confused with electromagnetic radiation (EMR).
EMR is a term used to describe the movement of electromagnetic energy through the propagation of a wave. This wave,
which moves at the speed of light in a vacuum, is composed of electric and magnetic waves which oscillate (vibrate) in
phase with, and perpendicular to, each other. This is in contrast to EMF, where the electric and magnetic components are
essentially independent of one another.
Whereas EMR causes energy to be radiated outwards from its source e.g. light from the sun or radio-frequency signals
from a television transmitter, EMFs cause energy to be transferred along electric wires. EMF bear no relationship, in their
physical nature or effects on the human body, to EMR such as x-rays or microwaves.
Where Do Electric and Magnetic Fields Occur?
Electric and magnetic fields occur both naturally and from man-made sources. They are not unique to high
voltage power lines.
Natural EMFs are associated with such things as lightning, solar activity or the earth’s magnetic field. All living
organisms, including humans, have natural electric charges, currents, and internal electric and magnetic fields.
Man made EMFs occur whenever electricity is being used in any form of electrical equipment or wiring. Most
people will be exposed to a wide variety of EMF sources throughout their daily lives in their homes, places of work
and the general environment.
Health Research
As electricity use is so widespread in modern society, questions about its possible effects on health are important to
everyone. EMFs have been the subject of thousands of scientific studies around the world over many years. Research
conducted over the past 35 years has significantly enhanced our knowledge of EMFs.
Biological and occupational health research began in the early 1960s. Since that time, many national and international
review panels, set up by bodies such as the World Health Organisation, the US National Institute of Environmental and
Health Sciences and the UK National Radiological Protection Board, have evaluated the research to assess the likelihood
of health effects being associated with exposure to electric and magnetic fields.
The World Health Organisation extensively reviewed scientific literature on EMF in 2007. The findings of their review are:
“Only acute effects have been established and there are two international exposure limit guidelines (ICNIRP, 1998 and
IEEE, 2002) designed to protect against these effects.
As well as these established acute effects, there are uncertainties about the existence of chronic effects, because of the
limited evidence for a link between exposure to ELF [Extremely Low Frequency] magnetic fields and childhood leukaemia.
Therefore the use of precautionary approaches is warranted. However, it is not recommended that the limit values in
exposure guidelines be reduced to some arbitrary level in the name of precaution. Such practice undermines the scientific
foundation on which the limits are based and is likely to be an expensive and not necessarily effective way of
providing protection.”
In Australia, the relevant health authority is the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), an
Australian Government agency. In response to a 2001 report, the CEO of this agency said:
“It is also important not to fixate on the location of external power lines, including high voltage transmission lines, as the
prime cause of exposure. Exposure to ELF magnetic fields can arise from ground currents, internal household wiring and
the use of electrical appliances as much as from exposure to external powerlines.”
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Electric and Magnetic Fields
Brochure
Government Agencies such as ARPANSA have also monitored international research on the topic, concluding that:
“The scientific evidence does not establish that exposure to ELF EMF found around the home, the office or near
powerlines and other electrical sources is a hazard to human health.”
As the possibility of adverse health effects cannot be ruled out entirely, TransGrid adopts a policy of “prudent avoidance”
towards EMF. This approach is consistent with the guidance provided by the World Health Organisation (2007):
“Provided that the health, social and economic benefits of electric power are not compromised, implementing very low
cost precautionary procedures to reduce exposure is reasonable and warranted.”
TransGrid’s Policy
TransGrid adopts a precautionary approach to the management of electric and magnetic fields by:
>> Taking electric and magnetic fields into account in
the design and location of new facilities
>> Closely monitoring ongoing research and
reviews by scientific panels and international
policy developments
>> Continuously reviewing our policies and practices in
light of the latest scientific information
>> Measuring field strengths in and around our own
installations and other places where appropriate
>> Providing up-to-date information to interested people
on request.
Electric and Magnetic Field Levels in the Modern Environment
The highest electric fields in the modern environment occur in the vicinity of high voltage electrical equipment. However,
for many years, it has been magnetic fields which have attracted the most interest in relation to health.
Magnetic fields exist wherever electricity is used. The range of magnetic field levels associated with a selection of
everyday electrical appliances, as well as utility installations, are shown below.
Typical magnetic field levels
Here is a guide to the relative strengths of magnetic fields in some common house hold appliances and electricity assets:
Hairdryer
10-70 mG
Kettle
2-10 mG
Laptop
2-20 mG
Under a distribution line
2-20 mG
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Toaster
2-10 mG
Directly under high voltage
transmission line
10-200 mG
Fridge
2-5 mG
Stove
2-30 mG
At the edge of high voltage
transmission line easement
2-50 mG
Electric Blanket
5-30 mG
Underground cables
5-200 mG
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Electric and Magnetic Fields
Exposure guidelines and limitations
The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) has adopted the International Commission
on Non-Ionizing Radiation Protection (ICNIRP) guidelines published in 2010 for limiting exposure to EMF. The ICNIRP
guidelines are one of two international guidelines recognised by the World Health Organisation and can be considered
international best practice. Accordingly, TransGrid follows these guidelines.
The ICNIRP guidelines stipulate separate “Basic Restrictions” for the general public and for occupational exposure. The
Basic Restrictions are set at levels well below those which could cause known acute health effects. However, as it is
difficult to measure compliance with these Basic Restrictions, ICNIRP also provide “Reference Levels” which are easy to
measure and can be assumed to ensure compliance with the Basic Restrictions without further investigation.
The ICNIRP Reference Levels are shown in the table below.
Electric Field
Magnetic Field
General Public Reference Levels
5kV/m
2,000mG
Occupational Reference Levels
10kV/m
10,000mG
ICNIRP acknowledge the conservatism associated with the Reference Levels and advise that they can be exceeded so
long as it can be demonstrated that the Basic Restrictions are not exceeded.
For more information
Phone
1800 222 537
Email
community@transgrid.com.au
Webwww.transgrid.com.au
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