The project presents a Montecarlo simulation in the non-dedicated programming software environment R to analyse the availability of a substation and provide support to the develop of tools for the assessment of availability calculation based on failures of components and availability of O&M resources. The work uses Montecarlo simulation to ensure variability in calculation and include uncertainty. A generic model of an offshore substation is prepared, and a case study is built from it. The availability of a substation is calculated based on failures of components and mobilization of resources and reparation time of components. Data and information are gathered with the support of experts from the industry. A sensitivity analysis is carried out to develop a discussion around the model and the results. The availability and other economic measures are calculated from the case study. The thesis work and the results provide a glance on the potential of the utilization, even at its early stage of development, of Montecarlo modelling technique to help to improve the confidence of experts in the evaluation of the availability for projects development.