128,372 research outputs found
Robust Operating Envelopes for DER Integration in Unbalanced Distribution Networks
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
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
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
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A UML-based static verification framework for security
Secure software engineering is a new research area that has been proposed to address security issues during the development of software systems. This new area of research advocates that security characteristics should be considered from the early stages of the software development life cycle and should not be added as another layer in the system on an ad-hoc basis after the system is built. In this paper, we describe a UML-based Static Verification Framework (USVF) to support the design and verification of secure software systems in early stages of the software development life-cycle taking into consideration security and general requirements of the software system. USVF performs static verification on UML models consisting of UML class and state machine diagrams extended by an action language. We present an operational semantics of UML models, define a property specification language designed to reason about temporal and general properties of UML state machines using the semantic domains of the former, and implement the model checking process by translating models and properties into Promela, the input language of the SPIN model checker. We show that the methodology can be applied to the verification of security properties by representing the main aspects of security, namely availability, integrity and confidentiality, in the USVF property specification language
A framework for security requirements engineering
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
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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