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The focus of the work presented here is to raise awareness of how ancillary services within the NordPool area could be of value in supporting the future grid, and who could be the provider of these services. The ancillary services considered here are not limited to the current market, but also services for future market solutions as well as services for fulfilment of grid codes. The goal is to promote the development of existing and novel solutions to increase the utilisation and thus the value of equipment within the power system. The paper includes a techno-economical categorisation of ancillary services, from a provider’s perspective, presenting opportunities and competition. Furthermore, procurers of services could utilise this kind of categorisation to identify possible providers or partners. The analysis of the categorisation shows a broad range of possible providers for each service and a broad range of possible services from each provider.

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Creating defense plans against extreme contingencies requires knowledge of the principal vulnerabilities of power systems. This paper describes the blackout phenomenon as a process with separate phases and distinctive transitions. The paper proposes two indicators that can help to identify vulnerabilities in a specific operating scenario and recommends that the dynamic behavior of a power system after successive faults should be analyzed. This analysis would reveal vulnerabilities connected to high impact low probability contingencies where the system response can change after several successive contingencies. These vulnerabilities cannot be captured by steady state analyses. Analyses of some recent large European blackouts, presented in the paper, indicate that a power system may collapse after only a limited number of contingencies, implying that these power systems are more vulnerable to multiple contingencies than the system operators may be aware of.Index Terms-blackout, cascading failure, N -1 criterion, power system security, power system stability, power transfer capacity

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