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Report RSE 17002136

Impact of severe weather events on the electrical system resilience



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R. Bonanno (RSE SpA), S. Sperati (RSE SpA), P. Marcacci (RSE SpA) , G. Stella (RSE SpA), M. Lacavalla (RSE SpA)

GRID RESILIENCE 2016 - Security and vulnerabilities of the electrical system


Characterize, predict and monitor intense meteorological phenomena is the way to define the expectedlevel of risk for the electricity transport network, when severe weather events are expected. Criticalevents of wet-snow, like the recent ones in the Abruzzo region, can be predicted in advance, but thepossible consequences on the transmission and distribution system depend on the overload of snowsleeve on the conductors. Integrated systems of warning and monitoring, like WILD WOLF, can providethis kind of information. These systems, along with mappings of direct and indirect meteorological risk for network infrastructure, may allow operators to implement operating strategies and appropriate work plans, aimed to an increase of the resilience of the electrical system and to promote the continuity and quality of the service.

In this work, a preliminary map of the snow and ice loads on the Italian territory is presented. The ice load map is an useful tool for the resilience assessment process of the entire electrical transmission system. This map was realized by processing the meteorological reanalysis dataset MESAN for wetsnow conditions in order to estimate the maximum ice load with a spatial resolution of 5x5 km. The values provided are related to the vertical loads of snow and ice, combined with the action of the wind, for linear meter of conductor.

The mapping has been elaborated for nine type of conductors and with return time varying between 10 and 50 years. A wind map on the whole Italian territory was also obtained by means of the 10 m wind speed variable available on MESAN dataset.

To overcome the problem of a correct forecast of the air temperature during wet-snow events in complex orographic regions like deep valleys, the study of statistical methods based on Analog Ensemble techniques (AnEn) was further deepened. These methodologies, previously applied by using the outputs of global weather models as ECMWF and GFS, have been applied with good results with limited area models outputs, using for the training and the verification meteorological data coming from some stations installed by RSE in collaboration with TERNA, in particularly significant areas for the sleeve formations.

The development of the new WebGIS for WOLF has been completed, and the forecast of the mechanical load due to snow sleeves over HV and MV overhead lines are now available for consultation. The study of the anti-icing currents at the WILD station was further deepened in order to suggest active mitigation solutions to electric operators, based on the Joule effect, optimized for each type of conductors.

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