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One of the main constraints for Renewable Energy Sources (RES) integration in LV networks are overvoltages caused by changing the normal power flow of the network. In favourable weather conditions high voltages may lead to overvoltage trips thus preventing the injection of renewable energy into the grid. An optimized management of power injection from controlled RES to keep the grid voltage within...
The proliferation of distributed energy resources (DER) in the distribution grid has brought many challenges to the Distribution System Operators (DSO), as they have to ensure that the growing share of DER can be safely connect to the power grid and still maintain the network's safety, continuity of service and power quality requirements. An interconnection protection relay, placed between the grid...
The paper describes the advantages and constrains of integrating of a fault location functionality to the system that is used by a dispatch center to operate a Smart Grid in the electricity distribution sector. An electricity distribution grid contains a large number of power lines and equipments distributed over a wide area that might be the size of an entire country (see Figure 1). A great number...
EDP Distribuição (EDP Group), is the mainland Portugal Distribution System Operator (DSO), with more than 6 million customers, over 400 HV/MV Substations, 60 thousand MV/LV Substations, 80 thousand km Network (HV/MV) and a LV Network about 140 thousand km. At the end of 2010, most of the substations had low impedance earthing at the MV level, although there was a set of substations, mainly located...
One of the main nightmare scenarios regarding Distributed Generation is islanding. In that event, the electrical Utility ceases to have control over the frequency and voltage levels in the island. However, it is still responsible for the quality of service rendered to its clients. To prevent the occurrence of islanding a protection function is used. In the Portuguese case only frequency protection...
The minimum phase-to-ground fault current required to be sensed by protection systems in medium-voltage (MV) networks can be as low as 0.7 A in a few countries, leading to a lot of undesired relay trips and poor service quality to costumers. However, these settings raise the protection threshold above the minimum fault current that concerns network operators regarding human safety, although they cannot...
Artificial Neutral Points made by oil-immersed reactors, particularly zigzag inductances, have been applied to limit earth fault currents in many MV distribution networks. ANPs can be overstressed both mechanically and thermally and a number of failures have been reported, particularly in overhead networks. A thermal analysis is performed which shows that present Standards requirements can underestimate...
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