p249 - Distributed Generation Impact on Voltage Sags in...

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Distributed Generation Impact on Voltage Sags in Distribution Networks Juan A. Martinez-Velasco Dept. Eng. Elèctrica - ETSEIB Universitat Politècnica de Catalunya Barcelona, Spain Jacinto Martin-Arnedo Depto. Distribución ITC2 L’Hospitalet de Llobregat, Spain Abstract — Characteristics of voltage sags caused by faults in distribution networks depend on the design of the protection system and the coordination between the different protective devices. The presence of distributed generation (DG) changes the radial nature of distribution systems, so it can affect the performance of the protection system, and consequently the characteristics of voltage sags. In addition, DG will help to maintain the during-fault voltages of healthy phases. This paper explores the impact that DG can have on voltage sags characteristics by means of a small test distribution network and presents a simple method to compare and rank the performance of protection systems. Keywords- Distributed Generation, Voltage Sag, Modelling, Power Distribution, Power Quality, Simulation. I. INTRODUCTION The growing penetration of distributed generation (DG) from renewable and traditional sources has raised some concerns about its impact on the operation of distribution systems. Although costs associated with DG technologies are still high, they can be a solution for those situations in which high power supply reliability is needed, or when the construction of transmission lines and large power plants is not supported by end-users [1] - [3]. The installation of DG sources raises new challenges to the operation of radial distribution networks. DG does not change the radial topology of these networks but the power will no longer flow in a single direction. This has an impact on the protection of distribution networks, and this impact depends on size, type and location of DG. According to a report of the IEEE Power System Relay Committee, the list of topics to be revised would include the lack of directional sensing of relays for radial systems, the islanded operation of DG, autoreclosing schemes, or breaker failures [4]. DG islanding is one of the main concerns [5] - [7], and although islanded operation is not generally allowed, DG may successfully operate in island if there is a balance between load and generation. Characteristics of voltage sags in distribution networks caused by faults are highly influenced by the placement of protective devices and the coordination between them. They are also affected by the presence of DG, although generators embedded in a distribution network can help to maintain during-fault voltages at the healthy phases. This paper explores the impact that DG can have on the characteristics of voltage sags considering the types of protective devices installed in the system and the coordination between them. The connections of the substation transformers and the DG
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p249 - Distributed Generation Impact on Voltage Sags in...

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