Aim of this research is to improve on a quantified partial equilibrium model developed by REKK describing the Central and South-East European electricity markets. The improved model determines the wholesale prices and the generation level of the power plants of 15 East and South-East European countries. The model takes into account the region's supply and demand features, the network constraints and perfect competition across borders and among power plants is assumed. By the model we can analyze both short and long term price development and we can also examine electricity trade flows in the region. Furthermore, we analyzed the electricity demand in each country giving us the opportunity to model equilibrium prices during different load hours. Finally, to get more realistic results, we investigated how one participant's strategic behavior (capacity withdraw) modifies the results, assuming that the other participants still behave as competitive i.e. with the model it is possible to find those actors on the market who has market power.