128,372 research outputs found

    Robust Operating Envelopes for DER Integration in Unbalanced Distribution Networks

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    Operating envelopes (OEs) have been introduced in recent years as a means to manage the operation of distributed energy resources (DERs) within the network operational constraints. OEs can be used by network operators to communicate DER dispatchable capacity to aggregators without further consideration of network constraints and are thus viewed as a key enabler for demand-side participation in future electricity markets and for ensuring the integrity of distribution networks. While a number of approaches have been developed to calculate OEs, uncertainties in system data are typically ignored, which can lead to unreliable results and introduce security risks in network operations. This paper presents a deterministic procedure to calculate robust OEs (ROEs) explicitly hedged against uncertainty and variability in customers' loads and generations. The approach is based on a geometric construction strictly included within the feasible region of a linear unbalanced three-phase optimal power flow problem that specifies the network operational constraints. The paper analyses and rigorously shows that the proposed approach also delivers proportional fairness in capacity allocations, and demonstrates how the ROEs can be enlarged by (i) exploiting the knowledge of customer operational statuses, and (ii) by optimising customers' controllable reactive powers. Two case studies based on an illustrative distribution network and an Australian representative low-voltage distribution network illustrate the efficiency and compliance of the proposed approach.Comment: Submitted to IEEE Transactions on Power System

    Towards a Rule Interchange Language for the Web

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    This articles discusses rule languages that are needed for a a full deployment of the SemanticWeb. First, it motivates the need for such languages. Then, it presents ten theses addressing (1) the rule and/or logic languages needed on the Web, (2) data and data processing, (3) semantics, and (4) engineering and rendering issues. Finally, it discusses two options that might be chosen in designing a Rule Interchange Format for the Web

    One Breaker is Enough: Hidden Topology Attacks on Power Grids

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    A coordinated cyber-attack on grid meter readings and breaker statuses can lead to incorrect state estimation that can subsequently destabilize the grid. This paper studies cyber-attacks by an adversary that changes breaker statuses on transmission lines to affect the estimation of the grid topology. The adversary, however, is incapable of changing the value of any meter data and can only block recorded measurements on certain lines from being transmitted to the control center. The proposed framework, with limited resource requirements as compared to standard data attacks, thus extends the scope of cyber-attacks to grids secure from meter corruption. We discuss necessary and sufficient conditions for feasible attacks using a novel graph-coloring based analysis and show that an optimal attack requires breaker status change at only ONE transmission line. The potency of our attack regime is demonstrated through simulations on IEEE test cases.Comment: 5 pages, 5 figures, Accepted to the IEEE PES General Meeting 201

    A framework for security requirements engineering

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    This paper presents a framework for security requirements elicitation and analysis, based upon the construction of a context for the system and satisfaction arguments for the security of the system. One starts with enumeration of security goals based on assets in the system. These goals are used to derive security requirements in the form of constraints. The system context is described using a problem-centered notation, then this context is validated against the security requirements through construction of a satisfaction argument. The satisfaction argument is in two parts: a formal argument that the system can meet its security requirements, and a structured informal argument supporting the assumptions expressed in the formal argument. The construction of the satisfaction argument may fail, revealing either that the security requirement cannot be satisfied in the context, or that the context does not contain sufficient information to develop the argument. In this case, designers and architects are asked to provide additional design information to resolve the problems

    Risk assessment for the installation and maintenance activities of a low-speed tidal energy converter

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    The study presented in this paper, is part of the Deep Green project, which includes the development of a power converter/device for employment in low-speed tidal currents. It mainly focuses on the initial steps to investigate the ways on how to minimize the risks during handling, operation and maintenance (O&M) activities of the full-scale device particularly in offshore operations. As a first tep, the full-scale device offshore installation and O&M tasks are considered. The overall risk analysis and decision making methodology is presented including the Hazard Identification (HAZID) approach which is complemented with a risk matrix for various consequence categories including personnel Safety (S), Environmental impact (E), Asset integrity (A) and Operation (O). In this way, all the major risks involved in the mentioned activities are identified and actions to prevent or mitigate them are presented. The results of the HAZID analysis are also demonstrated. Finally, the last section of this paper presents the discussion, conclusions and future actions for the above-mentioned activities regarding the full-scale device
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