This paper deals with the topic of modeling of the transmission power system, taking into account only the primary elements. The primary elements of the transmission network can include generators, transformers, lines and loads. These elements thematically deal with their functions in the system and the principle of operation. The elements of the same name differ in size and characteristics, which are subordinated to the needs of the network. As a result of the work, a model of a part of the transmission network was made. By modeling the system in software (software package), a virtual model of a real transmission network was created. With such an approach, we get the data needed to dimension the elements of a real system cheaper, faster and easier. In the NEPLAN software package, a model of the transmission network of the city of Zagreb with high-voltage lines (110 kV, 220kV and 400kV) was made. The work of the network throughout the year analyzes the flows of forces from which the network development plan is adopted. An additional analysis of energy consumption specifies the characteristic Wednesday in the winter and summer period when the maximum electricity consumption occurs. The network model was tested for short-circuit failure and conductor failure.