Electric and Magnetic Fields from
Underground Transmission Cabling
Transpower is aware that electric and magnetic fields associated with
its transmission network can raise concerns with the public.
The safety of the public and our staff is fundamental to our business
and our works are designed to comply with the international guidelines
recommended by the NZ Ministry of Health.
Where are electric and magnetic fields found?
Electric and magnetic fields (EMFs) are present
wherever there is electricity – including in the
home, office and worksite.
For example, EMFs are found near all electrical
wiring in your street and in your home, and are
associated with electric tools and most electrical
EMFs are also associated with the transmission
of electricity and transmission cables. Although
electric and magnetic fields are commonplace
in modern life, we are aware that electricity
transmission as a source of EMF is the focus of
much of the public concern.
What standard does Transpower apply to provide safe designs?
In managing electric and magnetic fields, Transpower follows the guidelines set by the
Transpower designs assets to meet the guidelines set by the International Commission on
Non-ionizing Radiation Protection (ICNIRP), which is part of the World Health Organisation.
These guidelines have been endorsed in New Zealand by the National Radiation Laboratory
(part of the Ministry of Health). They are also identified as the appropriate basis for public
health protection by Policy 9 of the National Policy Statement on Electricity Transmission
under the Resource Management Act.
What about EMFs from underground cables?
As with an overhead transmission line, the amount of electric power transmitted on an
underground cable at any given time is determined by its voltage and current.
Electric fields are determined by the voltage. In the case of an underground cable, electric
fields are screened by the cable sheath so would be eliminated above it.
Electric & Magnetic