Independent study on electricity transmission infrastructure published
Minister for Communications, Energy and Natural Resources Eamon Ryan TD today
published the independent Study on the Comparative Merits of Overhead Electricity
Transmission Lines Versu
s Underground Cables.
The Study was initiated in February of this year following calls from deputies from all
sides of the house, particularly those members of the Joint Oireachtas Committee on
Communications, Energy and Natural Resources for an independ
ent study to consider
the issues involved with both types of transmission infrastructure.
The study was conducted by international consultants Ecofys and Golder Associates,
a global group specialising in ground engineering and environmental services, in
artnership with an expert in underground cable technology.
A total of 522 submissions were received and reviewed by the consultants
undertaking the report. Current international practice and two hypothetical case
studies with route lengths of 100 km and
50 km were examined.
The study examined electricity transmission technologies, comparisons of technical
and economic characteristics, environmental and health impacts, policy implications
and costs. The study was not project specific and was designed to
inform decisions on
transmission infrastructure generally.
The key findings of the study are as follows:
Increasing pressure internationally has become an important driver for
underground cables as an alternative. The technology for underground cables
high voltages is continuing to develop.
International experience of laying such cables over long distances is limited
and the majority of existing projects do not represent transmission connections
in conventional networks such as we have in Ireland
rground cables can be expected to have forced outage rates which are at
least 10 times greater than that of overhead lines.
Underground cables are therefore severely limited in terms of transmission
adequacy and are not equivalent to overhead lines in ter
ms of security of
Work undertaken on the two case studies suggest that the capital cost of
constructing underground cables would be approximately 5 times greater than
the cost of overhead lines and 3 times the lifecycle costs
magnetic fields may be higher directly above an underground
cable than under overhead lines. Additional measures can reduce the magnetic
field for both options.
Ireland designs and operates transmission assets in line with World Health
guidelines. In Ireland magnetic field exposure directly
under a transmission line is generally 80
90% lower than the maximum levels
recommended in the WHO guidelines.
Both overhead and underground options have environmental impacts
Minister Ryan said,
“The Study demonstrates that decisions on these kinds of projects
need to take a wide range of complex technical, economic, environmental and other
considerations into account. My Department will now be arranging for the consultants
to present their findin
gs to the Joint Oireachtas Committee on Communications,
Energy and Natural Resources.
The Study was initiated in order to get an accurate and independent set of facts
regarding the technical, environmental, health and cost implications of overhead lines
relative to underground cables. This report provides these facts. I am confident that
this Study will assist all interested parties in current and future transmission projects”.