Browsing by Author "Syri, Sanna|Haarla, Liisa"

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Probabilistic reliability assessment in grid investment analysis
(2011) Kuusi, Risto
School of Engineering | Master's thesis
The main objective of this study is to discover whether probabilistic tools (software) may be used to accommodate the economic aspect of power system reliability in grid investment analysis. Another objective of the study is to gain a general overview of the available tools. The economic value of reliability is measured with the welfare loss to society due to the delivery interruptions of electricity (cost of energy not supplied) and the electricity generation re-dispatch cost due to grid constraints. This study examines eight probabilistic tools in a qualitative basis to determine the most suitable one for analysing the Finnish power system. The utilized evaluation criteria emphasize the capabilities of the tools for the assessment of electricity markets, the stochastic behaviour of power system components, power flow and system security. Furthermore, the compatibility with other power system planning tools will be considered. Based on the evaluation criteria, ASSESS model was considered the most suitable tool. Consequently, this study utilizes ASSESS to model the reliability effect of grid investments based on data from the Finnish power system. The power system operational states are simulated with a market-based approach and analysed with optimal AC power flow simulations (module TROPIC). The contingencies are generated by sampling random faults to the operational states. The severity of the contingencies is analysed with a quasi steady state approach considering slow voltage phenomena (module ASTRE). The method of utilizing ASSESS was mainly successful to describe the current power system. However, certain encountered deficits question the suitability of the method for investment analysis. First, performing AC power flow simulations in the market-based operational states descended into notable convergence problems in a future scenario. Second, the simulated consequences of the contingencies were not entirely convertible to economic value. Finally, the quasi steady state approach only assesses a certain set of stability phenomena. The mentioned challenges need to be acknowledged if using this method to accommodate the economic aspect of reliability in grid investment analysis.