The introductory part of this work describes the basic principles of wind energy conversion as well as electricity production from wind turbines. It contains a list and overview of internal and external parts of wind turbines. In addition to this different ways of connecting wind power plant to the electricity grid are described in addition to technical conditions which must be satisfied. Detail technical data related to the wind turbines; transformers and medium voltage cables used in the internal cable network is described for wind power plant „Krš - Pađene“.The cable routes and characteristic cross sections of cable ducts which lead to wind turbine substations and main supply substation are given. Depending on the number of connected wind turbines per feeder; the length of the feeder and the cable type; the calculation of the current sizing of the cables is described. For defined internal cable network detail power flow calculation is conducted using MATPOWER software package. The calculation uses the input data related to cable lines; transformers and buses electric parameters and produces results related to power flows; power cable line loading level; voltage increase and active power losses in the internal cable network.