Line Reliability, Climate Change and Extreme Weather"
Gibson Peters, Tony DiGioia Jr., P.E.,Chris Hendrickson, and Jay Apt
Transmission lines in service today in the US have been designed
using a multitude of design approaches and structural loading criteria.
The principal cause of structural failures is associated with weather
events that produce loads that exceed the structural loading design
criteria. In some cases, failures have been the result of inadequate
design, construction and/or maintenance practices, airplane or vehicle
accidents and criminal activities.
The cost of storm-caused transmission outages is significant, costing
utilities and users on the order of $270 million per year and $2.5
billion per year (2003 $ís) respectively. The cost of storm damages may
be under-appreciated by utilities and regulators since standard industry
reliability indices (SAIDI & SAIFI) omit the costs of large storm
Currently available data suggest that the frequency and severity of
hurricanes and ice storms will increase in the future. There has been a
doubling of Category 4 and 5 Atlantic hurricanes from 1970 to 2004 which
is the same time period during which ocean temperatures have increased.
If this trend continues, it will have a significant impact on utility
and user costs due to structural failures. Studies have shown that
increases in CO2 levels in the atmosphere could increase hurricane wind
velocities by about 10%, resulting in an increase in wind loading of
Under current policy, there is a lack of financial incentives for
transmission line owners to upgrade/uprate, refurbish and/or build new
lines. For example transmission line owners in restricted jurisdictions
do not incur penalties associated with user costs caused by storm
Based on the above observations and conclusions, recommendations are
made concerning the collection and scope of SAIDI & SAIFI data, the
adoption of a Survivability Design Concept, the adoption of transmission
line investment incentives and the revision of structural loading design
criteria manuals to include survivability design concepts and the
impacts of climate change.
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