System configuration, fault detection, location, isolation and restoration: a review on LVDC Microgrid protections

Low voltage direct current (LVDC) distribution has gained the significant interest of research due to the advancements in power conversion technologies. However, the use of converters has given rise to several technical issues regarding their protections and controls of such devices under faulty conditions. Post-fault behaviour of converter-fed LVDC system involves both active converter control and passive circuit transient of similar time scale, which makes the protection for LVDC distribution significantly different and more challenging than low voltage AC. These protection and operational issues have handicapped the practical applications of DC distribution. This paper presents state-of-the-art protection schemes developed for DC Microgrids. With a close look at practical limitations such as the dependency on modelling accuracy, requirement on communications and so forth, a comprehensive evaluation is carried out on those system approaches in terms of system configurations， fault detection, location, isolation and restoration

First performance evaluation of a Multi-layer Thick Gaseous Electron Multiplier with in-built electrode meshes - MM-THGEM

We describe a new micro-pattern gas detector structure comprising a multi-layer hole-type multiplier (M-THGEM) combined with two in-built electrode meshes: the Multi-Mesh THGEM-type multiplier (MM-THGEM). Suitable potential differences applied between the various electrodes provide an efficient collection of ionization electrons within the MM-THGEM holes and a large charge avalanche multiplication between the meshes. Different from conventional hole-type multipliers (e.g. Gas Electron Multipliers - GEMs, Thick Gas Electron Multipliers - THGEMs, etc.), which are characterized by a variable (dipole-like) field strength inside the avalanche gap, electrons in MM-THGEMs are largely multiplied by a strong uniform field established between the two meshes, like in the parallel-plate avalanche geometry. The presence of the two meshes within the holes allows for the trapping of a large fraction of the positive ions that stream back to the drift region. A gas gain above 10^5 has been achieved for single photo-electron detection with a single MM-THGEM in Ar/(10%)CH4 and He/(10%)CO2, at standard conditions for temperature and pressure. When the MM-THGEM is coupled to a conventional THGEM and used as first cascade element, the maximum achievable gains reach values above 10^6 in He/(10%)CO2, while the IBF approaches of 1.5% in the case of optimum detector-bias configuration. This IBF value is several times lower compared to the one obtained by a double GEM/THGEM detector (5-10%), and equivalent to the performance attained by a Micromegas detector.Comment: 11 pages, 8 figures. Submitted to JINS

Power system fault prediction using artificial neural networks

The medium term goal of the research reported in this paper was the development of a major in-house suite of strategic computer aided network simulation and decision support tools to improve the management of power systems. This paper describes a preliminary research investigation to access the feasibility of using an Artificial Intelligence (AI) method to predict and detect faults at an early stage in power systems. To achieve this goal, an AI based detector has been developed to monitor and predict faults at an early stage on particular sections of power systems. The detector only requires external measurements taken from the input and output nodes of the power system. The AI detection system is capable of rapidly predicting a malfunction within the system . Simulation will normally take place using equivalent circuit representation. Artificial Neural Networks (ANNs) are used to construct a hierarchical feed-forward structure which is the most important component in the fault detector. Simulation of a transmission line (2-port circuit ) has already been carried out and preliminary results using this system are promising. This approach provided satisfactory results with accuracy of 95% or higher

Quantum-dot based photonic quantum networks

Quantum dots embedded in photonic nanostructures have in recent years proven to be a very powerful solid-state platform for quantum optics experiments. The combination of near-unity radiative coupling of a single quantum dot to a photonic mode and the ability to eliminate decoherence processes imply that an unprecedented light-matter interface can be obtained. As a result, high-cooperativity photon-emitter quantum interfaces can be constructed opening a path-way to deterministic photonic quantum gates for quantum-information processing applications. In the present manuscript, I review current state-of-the-art on quantum dot devices and their applications for quantum technology. The overarching long-term goal of the research field is to construct photonic quantum networks where remote entanglement can be distributed over long distances by photons

Next-generation optical access seamless Evolution: concluding results of the European FP7 project OASE

Increasing bandwidth demand drives the need for next-generation optical access (NGOA) networks that can meet future end-user service requirements. This paper gives an overview of NGOA solutions, the enabling optical access network technologies, architecture principles, and related economics and business models. NGOA requirements (including peak and sustainable data rate, reach, cost, node consolidation, and open access) are proposed, and the different solutions are compared against such requirements in different scenarios (in terms of population density and system migration). Unsurprisingly, it is found that different solutions are best suited for different scenarios. The conclusions drawn from such findings allow us to formulate recommendations in terms of technology, strategy, and policy. The paper is based on the main results of the European FP7 OASE Integrated Project that ran between January 1, 2010 and February 28, 2013

Actor perception in business use case modeling

Mainstream literature recognizes the validity and effectiveness of use cases as a technique for gathering and capturing system requirements. Use cases represent the driver of various modern development methods, mainly of object-oriented extraction, such as the Unified Process. Although the adoption of use cases proliferated in the context of software systems development, they are not as extensively employed in business modeling . The concept of business use case is not a novelty, but only recently did it begin to re-circulate in the literature and in case tools. This paper examines the issues involved in adopting business use cases for capturing the functionality of an organization and proposes guidelines for their identification, packaging, and mapping to system use cases. The proposed guidelines are based on the principle of actor perception described in the paper. The application of this principle is exemplified with a worked example aimed at demonstrating the utility of the proposed guidelines and at clarifying the application of the principle of actor perception. The worked example is based on a series of workshops run at a major UK financial institution