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Simulation model of a protection scheme for active distribution networks

pubblicazioni - Articolo

Simulation model of a protection scheme for active distribution networks

L’articolo propone ed analizza, mediante simulazioni digitali in ambiente DIgSILENT Power Factory, uno schema di coordinamento delle protezioni di rete e di interfaccia dei generatori distribuiti per reti di distribuzione attive. Vengono inoltre descritti in dettaglio i modelli di simulazione sviluppati allo scopo.

A number of different drivers, such as improvements of power electronics, reduction of transmission and distribution costs, environmental issues and needs of diversifying power sources, is pushing a rapid increase of Distributed Generators (DG) connected to Medium Voltage (MV) distribution grids. The presence of large amounts of DG can interact with the grid and can have major impacts on the power quality. Some of the main interactions between DG and distribution grids are: reversal of power flow, harmonic pollution, voltage increase, voltage variations, flicker, nuisance trips/failures of grid protections, unwanted island operations. The paper, focusing on the last two phenomena, proposes a possible protection scheme suited for active distribution grids. Such a scheme makes use of directional line overcurrent relays and directional earth relays and introduces communications among grid protections and interface protections of DG. The main goals of the proposed solutions are: management of bidirectional power flows, logic selectivity, faulty line segment selection, reduced risk of unwanted island. The paper mainly deals with the implementation in the DIgSILENT Power Factory digital simulation environment of the proposed protection scheme. To this purpose, models of a typical urban MV distribution grid, of grid protections, of DG interface protections and of the communications systems have been developed. Digital simulations were performed to show the effectiveness of the proposed solution.

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