The paper deals with the issue of power flow analysis in transmission networks, using the Matpower 6.0 software package, within the Matlab programming environment. It presents the method of preparing input network data, setting the program’s calculation parameters, comparing the Newton-Raphson and Gauss-Seidel algorithms, and analyzing and presenting the calculation results. The calculation procedure for transmission networks of various sizes (16 to 300 buses) is presented, and the influence of capacitor banks on power flows, voltage conditions, and realized power losses is analyzed.