Coistas Vournas


Real-time Measurement-based Identification of Voltage Instability

This presentation will start with a short introduction to Voltage Stability concepts followed by an overview of Global vs Local Voltage Instability Detection approaches including a critical review of Impedance matching based methods and their limitations. Then the LIVES method (Local Identification of Voltage Emergency Situations) will be shortly presented and shown to provide a local detection of global stability by monitoring the LTC voltage recovery. The extension of this method to the New LIVES Index (NLI) that is based on local measurements at a transmission corridor will follow. This method is based on monitoring the change of transferred active power relative to the increase of apparent conductance (ΔP/ΔG). A particular application to obtain a transmission-line Relay-Based Index will be also discussed. All methods will be validated using simulation of an IEEE test system for Voltage Security Assessment.

Harnessing Distributed Reactive Support for Voltage Stability

This presentation focuses on harnessing reactive support from distributed resources, in order to increase the maximum power transfer to a weak area of a power system.The model used incorporates the distributed resources (with practically instantaneous reactive power controls in the quasi-steady-state, long-term dynamic simulation of a power system, in which also transformer Load Tap Changers (LTC), switching capacitor banks are included. Indicative MV feeders are simulated as case studies to assess the reactive support they can provide to a weak transmission corridor. Various types of distributed optimization are presented to coordinate active and reactive support.

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