1. The challenges of undergrounding of
4th  Annual Symposium
of the Hellenic Association for Energy Economics (HAEE)
The challenges of undergrounding of
high and ultra-high voltage cables in SE Europe
Georgia ILIOPOULOU
Surveying Engineer, Beng, MEng
National Technical University of Athens, Greece
Prodromos PSARROPOULOS
Structural & Geotechnical Engineer, BEng, MEng, MSc, PhD
Athens – 8 May 2019

2. Electricity projects in SE Europe
Large-scale electricity production projects
have been constructed and planned in SE Europe
( onshore and offshore )
New power-plant
in north Greece
Submarine cables to connect Israel, Cyprus and Greece

3. Transmission of electricity
The transmission of electricity
from onshore production sites to various consumers
takes mainly place via high and ultra high voltage above ground ( overhead ) cable grids,
which consist Critical Infrastructures
Above ground ( overhead )
cable grids

4. Transmission of electricity
The above ground ( overhead ) grids
are generally unacceptable
for the general public because of
their social and environmental impact.
More specifically:
visual pollution
electromagnetic radiation
structural vulnerability

5. Social and environmental impact Examples of visual pollution
Visual pollution may be detrimental
for the culture and tourism

6. Social and environmental impact Electromagnetic Radiation
Electromagnetic Radiation may have an impact
on the public health and safety

7. Social and environmental impact Structural Vulnerability
Structural vulnerability due to earthquakes, storms etc

8. Undergrounding cable grids
The most modern way to
eliminate optical pollution
and/or reduce electromagnetic radiation
is via the undergrounding of
high and ultra-high voltage grids.
A buried cable grid

9. Undergrounding cable grids Installation Techniques
The new manufacturing and installation techniques Include (ICF, 2003):
Reducing the dimensions and weights of HV and UHV (UltraHighVoltage) cables by using materials such as cross-linked polyethylene (XLPE).
Mechanical placement methods that avoid extensive excavation and material transfer.
Methods of installing cables without "defects" that respect the preservation of the characteristics of the environment into which they are imported. There are many different methods of installing cables. Each method used depends on a number of factors Including land use and different environmental characteristics.

10. Example of underground cables in Europe
It is noted that in some EU countries ( e.g. Germany )
the usage of buried cables has already been started.
SuedLink project is a 700 km HVDC underground cable
that will transport energy generated in wind parks
in northern Germany to southern Germany.

11. Implications of undergrounding cable grids
However, the “solution” of undergrounding cable grids
involves some technical or techno-economical implications.
More specifically:
a) overheating of cables
b) exposure to human interference
( unintentional or intentional )
potential geohazards
relatively high cost

12. Geohazards & undergrounding cable grids
Depending on the local
geological, topographical ( and seismological ) conditions,
various geohazards may be present
geohazards under static conditions
( karstification, landslides, rockfalls, ground settlements, erosion, river crossings, etc.)
b) earthquake-related geohazards
( active seismic faults, earthquake-triggered landslides, and soil liquefaction phenomena )

13. Examples of geohazards
special soils ( turf ) in Greece
erosion in Israel
sinkhole in Guatemala
mud volcanoes in Azerbaijan

14. Examples of geohazards landslide in California
landslide in Taiwan
landslide in California

15. A hypothetical case study
Route optimization of an underground cable
in north Peloponnese, Greece
taking into account the potential geohazards

16. A hypothetical case study
Route optimization of an underground cable
in north Peloponnese, Greece
taking into account the potential geohazards
Map of seismicity of
the Corinthian Gulf
in the period
Map of landslides of the Corinthian Gulf

17. A hypothetical case study
Route optimization of an underground cable
in north Peloponnese, Greece
taking into account the potential geohazards
Map of susceptibility to liquefaction of the geological formations of the Corinthian Gulf
General view of
a seismic fault

18. A hypothetical case study
Route optimization (and cost analysis)
was based on a GIS-based tool
that has been developed for this purpose

19. General conclusions Above ground ( overhead ) electrical cables
may have a social and environmental impact.
Undergrounding of electrical cables has been used
in various countries as an alternative to overhead cables.
It is evident that
the construction cost of undergrounding is higher
than the corresponding cost of aerial cables
( depending on the local conditions and the geohazards ).
Nevertheless, the total cost of undergrounding is not that high since the direct and indirect environmental benefits and economic impacts may be very important.

20. Thank you for your attention