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This paper presents a methodology to evaluate the contribution of wind farms (WFs) to the short-circuit level of high-voltage substations. The method relies on simplified equivalent WF models suitable for integration in commercial network-analysis software platforms. The developed WF models are especially suitable for integration in PSS/E and they can be incorporated in models of large power systems. The methodology can be applied to all kinds of WFs regardless of the type of the wind turbines used. Finally, the proposed models are verified through detailed simulations and a case study concerning short-circuit level calculation at all 150-kV and 400-kV buses of the Greek power system is presented. The relevant results are presented and general conclusions are extracted. Index Terms--Short-circuit level, wind farm (WF) modeling, WFs, wind integration.

Wind-power penetration in many cases faces significant barriers due to limited transmission capability. In Greece (and in most countries in Europe), the guaranteed access to the grid offered to wind parks, in conjunction with the existing planning practices, has led to severe limitations in wind power installed in certain congested areas. This paper presents some simple ideas that are currently being applied to the Hellenic Interconnected System, in order to increase the wind-power penetration. The main concept is the introduction of interruptible generator contracts and the control of the power flow through congested corridors by issuing power reduction commands, whenever security limits are violated. The proposed control is implemented using common PLCs of low cost and the existing SCADA system, and is both simple and transparent. The paper presents also a methodology to assess the impact of the proposed techniques on the wind penetration achieved. Index Terms--Grid integration, on-line monitoring and control, security assessment, transfer capacity, wind-power penetration.

A review of the literature published in 2010 on topics relating to wastewater treatment innovations in the areas of modeling, instrumentation, automation and optimization of wastewater treatment is presented. [ABSTRACT FROM AUTHOR]