Power outage related statistics in Sweden since the early 2000s and evaluation of reliability trends

This paper presents statistics based on over 15 years of power outage related data in Sweden collected by the national regulatory authority (NRA). In the early 2000s, Sweden introduced its first economic incentive scheme regarding continuity of supply (CoS) for power distribution system operators (DSO). For this purpose, the NRA began to collect power outage data from each DSO on an aggregated level. A few years later, in 2005, a severe hurricane struck Sweden that highlighted the vulnerability of the Swedish power system, resulting in a new regulatory framework related to power outages. To be able to effectively monitor the CoS in Sweden, the NRA began in 2010 to collect data on power outages on a customer level. Since 2012 a new revenue cap regulation with economic CoS incentives was implemented with major revisions from 2016 and 2020 respectively.The amount of detailed data available enables the NRA to closely monitor the CoS in the Swedish power grid. As a result of the stricter rules on power outages, there have been major investments in more reliable power distribution systems over the past decade. A positive tendency can be seen even if the CoS fluctuates from year to year due to e.g. weather events. The CoS is slightly better for years with mild weather and the impact on the CoS is less negative for years with severe storms, even if it is still far from good enough. The aim of this paper is to publish statistics with some concluding remarks from the NRA. We believe that sharing our experiences from Sweden may be of value for others, e.g. when developing new laws and regulations. The paper also contributes by informing about available data related to Swedish power outages for others to use when comparing countries or developing probabilistic models.