no single set of metrics is suitable for assessing energy security for all purposes in all situations for these country groups table outlines important factors contributing to energy insecurity of a nation region or particular group of countries energy security in this framework is defined as low vulnerability of vital energy systems the vulnerability of a system is the degree to which that system is unable to cope with selected adverse events such a framework allows review of security of vital energy systems from the perspectives of such criteria as criticality likelihood of the event and level and type of damage