Due to increasing consumption of electric energy, the distribution network is constantly expanding, so is very important that the network is properly planned.
Firstly, the problem of voltage drops is explained, which is one of the main reasons why network analysis is needed. Then, a theory of power flow between two nodes is described where a derivation of the equations used in the analysis of power flow is presented. An analysis of power flow would not be possible without the iterative methods. Gauss, Gauss-Seidl, decoupled and fast decoupled methods are presented. The main focus is placed on Newton-Raphson's method, which is suited for analysis in the distribution network. Then an overview of planning criteria for medium and low voltage network development is made. Technical criteria, such as voltage drops limitations, loading of distribution lines and transformers have been described. The criteria for low voltage network is relatively new, because it takes into account increase of consumption due to electrification of heating and traffic and the impact of diffuse sources. Also Gredos software is presented, which is the main tool for network planning and analyzing in Slovenian distribution companies.
Finally, an example of using Gredos is shown. An example of a low voltage network with 31 customers was selected, which was used to prepare the model in the Gredos software. Using the developed model, an analysis of the existing state of operation and state of operation with increased network load due to domestic charging stations, heating pumps and solar power stations is made. The analysis showed that the current state corresponds the technical criteria. The load with 16 electric car charging stations would not correspond the criteria. Also the load with 16 electric car charging stations and 16 heating pumps would not correspond the criteria. There were too high voltage rises in state with 16 solar power plant. In operational states with different combinations of load network corresponds the criteria.
The network should be strengthened at too high loads or consumers, which can adjust their own load to network load, should be involved.