Probabilistic power flow as an element of planning methodology

The deterministic criteria are the crucial element of current transmission and distribution system long term planning methodology in Poland. Transmission system in that process means 400, 220 and 110 kV network, in which the last one is formally classified as a distribution grid (regarding to ownership), however technically is highly meshed with the rest. Sometimes 110 kV network is called sub-transmission network. From the perspective of planning process both networks have to be analyzed together. During previous CIGRE Session it was mentioned about some methodological improvements in Poland, which were related to optimal power flow. It could be recognized also as a first step of improvement [5]. The next one might be connected with probabilistic power flow (PPF). Preliminary scientific research study have been conducted in that scope. Different methodologies of calculation PPF were compared. Probabilistic approach is widely used around the world, but the scope of usage is quite different [2,3,7,9]. It could covers the area from demand side to generation side (specially for RES), including infrastructure availability, and probabilistic criteria as well. There are three main approaches to PPF: approximation, analytical and numerical. The numerical is the most popular worldwide according to IT technology fast development and accuracy of results. For the transmission system in Poland can be considered to use a probabilistic approach, whereby due to the limitations of analical methods it is proposed to apply numerical methods. As an open issue remains the method of simulation - MonteCarlo Method, Stratified Sampling Method or the others.