New strategical trends in the architecture and safety of a low voltage distribution network

The low voltage network used to have a very simple technological complexity. The latest trends lead to some modification in this situation, as the one due to the dispersed generation (modifying the usual direction of energy from one way to two ways) or even its use as communication support (modifying the technologic composition with more than cables, boxes and fuses). Studies already done on the Lisbon network indicated as a more advantageous alternative a radial network architecture that avoids cable branches for the customers, or in some situations a network architecture with LV feeders between two transformers. This philosophy of network necessarily leads to an update of technological equipment. Several collaborative studies took place between Lisbon University and Imperial College of London concerning earth systems and protection systems in order to increase the safety and to make the conversion to a "TN" earthing system (neutral and protective single earthing) with opening meshed network (radial operation). The application of developed theoretical studies firstly were executed in Telheiras (new residential area in Lisbon) network with tests and analysis of values and neutral connections between transformers of the distribution substations (convergence to a single earth at Lisbon). We started a systematic program with incidence on the network architecture in order to achieve a strong reduction on the LV switching boxes needed and to solve a lot of traditional problems