Technical infrastructure networks as socio-technical systems : Addressing infrastructure resilience and societal outage consequences

Abstract: Research area: Modern society is increasingly dependent on a range of technical infrastructure networks including e.g. power, transport and IT networks. This dependence is illustrated by large disturbances which from time to time affect these systems, often to an extent which few did consider possible.The overarching aim of this thesis is to advance analysis methods concerning large disturbance events in technical infrastructure networks. Work is performed in three areas: 1) modelling of technical infrastructure networks to enable exploration of resilience with respect to large disturbance events, 2) development of resilience metrics for assessment of impact on performance of technical infrastructure networks from system parameter changes given largedisturbance events and 3) quantification of societal consequences of electricity outages.Methods: The model for simulation of restoration processes of networks consists of two sub-models, one representing the infrastructure network and one representing the repair system. This enables explicit assessment of impact on system performance from technical as well as non-technical decision variables. The model is used for three case study systems and six quantitative resilience metrics are evaluated, three of them being developed and presented for the first time in the thesis. Quality of supply regulations as well as the Swedish Styrel system are used for contrasting societal consequences of electricity outages. A study is performed in which the regulations are used to determine and contrast the weights of electricity customers. Conclusions: The work presented in the thesis enables modelling of restoration processes of electricity and IT networks. In contrast to previous models used for this purpose, the developed model can simultaneously consider many simultaneous failures, prioritization of repairs and levels of repair system resource and their variation over time, enabling exploration of system performance with respect to several crucial resilience metrics. Three metrics: margin and sensitivity1 and 2 are found to be useful for quantitative assessment of impact on system performance from parameter changes. The case studies on societal consequences of electricity outages show that the contrasted consequence metrics are often not in agreement, posing the question if Swedish quality of supply regulations need to be adjusted to better consider some aspects of societal electricity outage consequences.