1,721,076 research outputs found
Manlio Rossi-Doria, le scienze sociali, l'economia italiana: risultati di un primo scavo nell'archivio
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Nature and Causes of CAP Changes in the 80s and a Tentative Exploration of Potential Scenarios
No full textBalancing Protection Dependability And Security In Large Transmission Grids
No full textAlthough main characteristics of supergrids and smart grids have not been univocally identified
yet, it can be foreseen that the networks of the future will be generally characterized by more sensors,
computation, ICT, monitoring and control functions. In such scenario, it is foreseeable that ordinary
power system components will be improved in order to develop more complex on-line control
functions. Experience with past severe cascading events showed how in many cases a selective
approach to system protections could have avoided blackouts, or mitigated their impact.
In this paper, a method is proposed to automatically adjust tripping zones of relays in order to
balance protection system dependability versus the functional security of the system. A nonlinear
programming technique is proposed for avoiding improper tripping of distance relays. The approach
aims to modify the settings of the protection system (i.e. distance relays) in order to guarantee that no
contingency can cause line tripping due to large swings. The tuning of protection schemes can be
operated in a “preventive control fashion”, ensuring transient/voltage stability and keeping system
trajectories off the tripping areas of distance relays (practical stability) with respect to selected major
contingencies.
Control actions (relay settings) are evaluated through the formulation and the solution of a
nonlinear optimization problem. Time domain simulations associated to the optimization problem
embed distance relay in the dynamic system representation. The approach treats concurrently, in the
same optimization problem, multiple contingencies. In this way, it is possible to find out the best
compromise between dependability and security during contingency analysis. The procedure can be
applied in the extended real-time control framework of power system operation or, simply, whenever
stressed conditions are experienced in the power system.
Test results are provided for a test case based on a representation of the Italian power grid,
along with a relevant part of the UCTE power system, during the transient that conducted to the 2003
Italian blackout. The computational burden associated is limited since basically it consists in time
domain simulations of transients caused by contingencies selected after contingency screening. Since
only tripping areas are modified no operative costs are associated to this security function
Between Scylla and Charibdys: Agricultural Economists' Navigation around Protectionism and Free Trade
No full textSulle Tecnologie WAMS per il controllo della Sicurezza di Sistemi di Trasmissione: un esperimento su scala continentale
No full textPreventing Blackouts through Reactive Rescheduling under Dynamical and Protection System Constraints
No full textThe 28 September 2003 blackout in Italy raised doubts about the ability of distance relays in distinguishing voltage collapse and remote short-circuits. The combined presence of reduced voltages and high power flows may trigger distance relays, with the consequent tripping of healthy lines, reducing the system survivability. The paper addresses an analysis of the behavior of distance protections during the sequence of events that led to the separation of the Italian network from the UCTE. An approach based on reactive power redispatching, aimed at mitigating the effects of cascading events, is presented. The proposed methodology allows to reduce the need for remedial control actions such as load/generation shedding which have a major economical impact. The proposed approach evaluates control actions aimed at ensuring stability and keeping system trajectories off the tripping zones of distance relays. Test results are obtained by implementing this methodology on a test case based on the Italian power system configuration
Contribution to the preferential subject 2: Transmission constraints, Equipment and special system to control transmission constraints -Discussion on report C2-208: A Dynamic Optimization Approach for Wide-Area Control of Transient Phenomena
No full textDiscussion on report C2-208: A Dynamic Optimization Approach for Wide-Area Control of Transient Phenomena
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