bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of yearling, juvenile and adult survival on reef manta ray (Manta alfredi) demography
Authors: Smallegange Isabel M. , van der Ouderaa Isabelle B.C. , Tibiriçá Yara
Published: August 2016

Background

The trade in manta ray gill plates has considerably increased over the last two decades. The resulting increases in ray mortality, in addition to mortality caused by by-catch, has caused many ray populations to decrease in size. The aim of this study was to ascertain how yearling and juvenile growth and survival, and adult survival and reproduction affect reef manta ray (Manta alfredi) population change, to increase our understanding of manta ray demography and thereby improve conservation research and measures for these fish.

Methods

We developed a population projection model for reef manta rays, and used published life history data on yearling and juvenile growth and adult reproduction to parameterise the model. Because little is known about reef manta ray yearling and juvenile survival, we conducted our analyses using a range of plausible survival rate values for yearlings, juveniles and adults.

Results

The model accurately captured observed variation in population growth rate, lifetime reproductive success and cohort generation time in different reef manta ray populations. Our demographic analyses revealed a range of population consequences in response to variation in demographic rates. For example, an increase in yearling or adult survival rates always elicited greater responses in population growth rate, lifetime reproductive success and cohort generation time than the same increase in juvenile survival rate. The population growth rate increased linearly, but lifetime reproductive success and cohort generation time increased at an accelerating rate with increasing yearling or adult survival rates. Hence, even a small increase in survival rate could increase lifetime reproductive success by one pup, and cohort generation time by several years. Elasticity analyses revealed that, depending on survival rate values of all life stages, the population growth rate is either most sensitive to changes in the rate with which juveniles survive but stay juveniles (i.e., do not mature into adults) or to changes in adult survival rate. However, when assessing these results against estimates on population growth and adult survival rates for populations off the coasts of Mozambique and Japan, we found that the population growth rate is predicted to be always most sensitive to changes in the adult survival rate.

Discussion

It is important to gain an in-depth understanding of reef manta ray life histories, particularly of yearling and adult survival rates, as these can influence reef manta ray population dynamics in a variety of ways. For declining populations in particular, it is crucial to know which life stage should be targeted for their conservation. For one such declining population off the coast of Mozambique, adult annual survival rate has the greatest effect on population growth, and by increasing adult survival by protecting adult aggregation sites, this population’s decline could be halted or even reversed.
Alongcoast structure and interannual variability of seasonal midshelf water properties and velocity in the Northern California Current System
Authors: Hickey B. , Geier S. , Kachel N. , Ramp S. , Kosro P. M. , Connolly T.
Published: August 2016

Moored sensors were maintained for ∼5 years on the northern California Current System (CCS) midshelf. The alongcoast sensor array spanned the area of influence of the plume from the Columbia River, several submarine canyons, as well as a coastal promontory where the equatorward coastal jet frequently separates from the shelf. Upwelling‐favorable wind stress magnitude decreases poleward by more than a factor of three over the latitudinal range and shelf width varies by a factor of two. In spite of the alongcoast structure in setting, both seasonal and interannual patterns in subsurface layer water properties were remarkably similar at all sites. Higher in the water column, freshwater forcing was substantial. Because of the near surface freshwater input, seasonal sea surface and subsurface temperatures were almost perfectly out of phase in the northernmost CCS, with a mid water column inversion in winter. Year to year differences in subsurface layer wintertime water properties were similar to spatial and temporal patterns of wind stress variability: little alongcoast structure except in salinity, but pronounced interannual differences strongly related to local wind stress. Summertime wind and subsurface property patterns were the opposite of those in winter: pronounced alongcoast wind stress structure, but little or no alongcoast or interannual variability in water properties, and only a weak relationship to local wind stress. Summertime interannual water property variability, including source waters, was shown to be more consistent with “remote forcing” via larger scale wind stress rather than with local wind stress, particularly in the northernmost CCS.
Conservative transport upscaling based on information of connectivity
Authors: Tyukhova Alina R. , Willmann Matthias
Published: August 2016

Connected structures in highly heterogeneous hydraulic conductivity fields lead to channels and preferential pathways for the main fluid flux and fastest solute particles. Their spatial complement is zones of slow advection, where solutes are delayed, causing tailing of solute breakthrough curves. These delays depend on the inclusion's size and the hydraulic conductivity contrast between inclusion and channel. The interplay between channels and small‐scale low conductivity inclusions leads to anomalous transport at larger scales. We test whether a simple separation of transport processes between channels and inclusions could be used to parameterize an effective transport model accounting for anomalous transport. Effective transport is represented by a multirate mass transfer model (MRMT): fast channel transport is controlled by parameters of the mobile zone, while slow advective delays are controlled by parameters of the mobile‐immobile exchange. We delineate the connected channels and analyze their connectivity followed by characterizing the low conductivity inclusions. We parameterize a MRMT model using connectivity and the statistics of the low permeable inclusions. Finally, we compare the parameterized MRMT with detailed numerical simulations in heterogeneous hydraulic conductivity fields with a clear separation between connected channel network and inclusions. In intermediately connected hydraulic conductivity fields only the cut‐off time of the tails is represented while early and intermediate time behavior is not reproduced. We suggest that an effective model for the latter case should account for additional processes like variability in advective velocity.
The world's biggest gamble
Authors: Rockström Johan , Schellnhuber Hans Joachim , Hoskins Brian , Ramanathan Veerabhadran , Schlosser Peter , Brasseur Guy Pierre , Gaffney Owen , Nobre Carlos , Meinshausen Malte , Rogelj Joeri , Lucht Wolfgang
Published: August 2016

The scale of the decarbonisation challenge to meet the Paris Agreement is underplayed in the public arena. It will require precipitous emissions reductions within 40 years and a new carbon sink on the scale of the ocean sink. Even then, the world is extremely likely to overshoot. A catastrophic failure of policy, for example, waiting another decade for transformative policy and full commitments to fossil‐free economies, will have irreversible and deleterious repercussions for humanity's remaining time on Earth. Only a global zero carbon roadmap will put the world on a course to phase‐out greenhouse gas emissions and create the essential carbon sinks for Earth‐system stability, without which, world prosperity is not possible.
Tremor and its duration‐amplitude distribution at Popocatépetl volcano, Mexico
Authors: Arámbula‐Mendoza R. , Valdés‐González C. , Varley N. , Reyes‐Pimentel T. A. , Juárez‐García B.
Published: August 2016

The duration‐amplitude distribution was calculated for the tremor observed at Popocatépetl volcano during episodes of activity in 2000 and 2012–2014. An exponential function was used to obtain a good fit for the duration‐amplitude distribution, and the source of volcanic tremor is probably generated by the transportation of magmatic fluids and its coupling with the host rock within the volcanic conduit. In particular, harmonic tremor has shown large amplitudes, durations, and mean values of amplitude, more than spasmodic or pulsating tremor. This is due to different generation mechanisms: in the case of harmonic tremor, it is produced during magma ascent and lava dome growth, while spasmodic and pulsating tremors are associated with fragmentation of the lava dome and gas emissions. This paper presents the duration‐amplitude distribution as a method to estimate the intensity of the tremor at Popocatépetl, a volcano with the major risk in all Mexico.
High‐temperature deformation of enstatite aggregates
Authors: Bystricky M. , Lawlis J. , Mackwell S. , Heidelbach F. , Raterron P.
Published: August 2016

Synthesized polycrystalline enstatite samples were deformed in a Paterson gas‐medium apparatus at 1200–1300°C, oxygen fugacity buffered at Ni/NiO, and confining pressures of 300 MPa (protoenstatite field) or 450 MPa (orthoenstatite field). At both confining pressures, the mechanical data display a progressive increase of the stress exponent from n = 1 to n~3 with increasing differential stress, suggesting a transition from diffusional to dislocation creep. Nonlinear least squares fits to the high‐stress data yielded dislocation creep flow laws with a stress exponent of 3 and activation energies of 600 and 720 kJ/mol for orthoenstatite and protoenstatite, respectively. Deformed samples were analyzed using optical microscopy and scanning and transmission electron microscopy. Microstructures show undulatory extinction and kink bands, evidence of dislocation processes. Crystallographic preferred orientations measured by electron backscatter diffraction are axisymmetric and indicate preferential slip on (100)[001]. Most deformed grains comprise an interlayering of orthoenstatite and clinoenstatite lamellae. While many lamellae may have formed during quenching from run conditions, those in samples deformed in the orthoenstatite field are often bordered by partial [001] dislocations, suggesting transformation due to glide of partial [001] dislocations in (100) planes. Comparison of our orthoenstatite creep law with those for dislocation creep of olivine indicates that orthoenstatite deforms about a factor of 2 slower than olivine at our experimental conditions. However, as orthoenstatite has a higher activation energy and smaller stress exponent than olivine, this strength difference is likely smaller at the higher temperatures and lower stresses expected in much of the upper mantle.
Mesoscale modulation of air‐sea CO2 flux in Drake Passage
Authors: Song Hajoon , Marshall John , Munro David R. , Dutkiewicz Stephanie , Sweeney Colm , McGillicuddy D. J. , Hausmann Ute
Published: August 2016

We investigate the role of mesoscale eddies in modulating air‐sea CO2 flux and associated biogeochemical fields in Drake Passage using in situ observations and an eddy‐resolving numerical model. Both observations and model show a negative correlation between temperature and partial pressure of CO2 (pCO2) anomalies at the sea surface in austral summer, indicating that warm/cold anticyclonic/cyclonic eddies take up more/less CO2. In austral winter, in contrast, relationships are reversed: warm/cold anticyclonic/cyclonic eddies are characterized by a positive/negative pCO2 anomaly and more/less CO2 outgassing. It is argued that DIC‐driven effects on pCO2 are greater than temperature effects in austral summer, leading to a negative correlation. In austral winter, however, the reverse is true. An eddy‐centric analysis of the model solution reveals that nitrate and iron respond differently to the same vertical mixing: vertical mixing has a greater impact on iron because its normalized vertical gradient at the base of the surface mixed layer is an order of magnitude greater than that of nitrate.
The effect of Kuroshio Current on nitrate dynamics in the southern East China Sea revealed by nitrate isotopic composition
Authors: Wang Wentao , Yu Zhiming , Song Xiuxian , Wu Zaixing , Yuan Yongquan , Zhou Peng , Cao Xihua
Published: August 2016

In spring 2014 (May–June), in the southern East China Sea (ECS) and east of Taiwan, nutrient and isotope samples were collected and analyzed. Also, dissolved oxygen (DO), chlorophyll‐a, and physical parameters were determined. The Kuroshio subsurface water intruded into the ECS and separated into two branches on the continental shelf: the nearshore Kuroshio branch current (NKBC) and the offshore Kuroshio branch current (OKBC). Nitrate concentration in the Kuroshio subsurface water slightly decreased east of Taiwan by assimilation and was supplied by upwelling currents northeast of Taiwan. The variations of DO, nitrate, and nitrogen isotopes in the bottom water showed that continuous nitrification occurred in the NKBC after intrusion into the ECS. This process might contribute to the hypoxia zone near the coast of Zhejiang Province, China. Our results also indicated that internal nitrogen cycles appeared in NKBC since the isotope fractionation ratio of oxygen and nitrogen (18ɛ:15ɛ) in
was 1.40. The
flux and budget were calculated in the NKBC via numerical simulations. It demonstrated that at least ∼0.52 kmol
·s−1 was produced by nitrification from DH9 to DH5 transect, and ∼0.11 kmol
·s−1 was consumed in the DH4 transect. Moreover, according to the Rayleigh model, primary production in most of southern ECS was supported by the intrusion of the Kuroshio subsurface water, causing 5‰ isotope fractionation. In some of nearshore stations which located in the northern investigated area, the assimilated nitrate was contributed from both the NKBC and coastal currents originated from the Changjiang diluted water.
Forcing of recent decadal variability in the Equatorial and North Indian Ocean
Authors: Thompson P. R. , Piecuch C. G. , Merrifield M. A. , McCreary J. P. , Firing E.
Published: August 2016

Recent decadal sea surface height (SSH) variability across the Equatorial and North Indian Ocean (ENIO, north of 5°S) is spatially coherent and related to a reversal in basin‐scale, upper‐ocean‐temperature trends. Analysis of ocean and forcing fields from a data‐assimilating ocean synthesis (ECCOv4) suggests that two equally important mechanisms of wind‐driven heat redistribution within the Indian Ocean account for a majority of the decadal variability. The first is the Cross‐Equatorial Cell (CEC) forced by zonal wind stress curl at the equator. The wind stress curl variability relates to the strength and position of the Mascarene High, which is influenced by the phase of the Indian Ocean Subtropical Dipole. The second mechanism is deep (700 m) upwelling related to zonal wind stress at the equator that causes deep, cross‐equatorial overturning due to the unique geometry of the basin. The CEC acts to cool the upper ocean throughout most of the first decade of satellite altimetry, while the deep upwelling delays and then amplifies the effect of the CEC on SSH. During the subsequent decade, reversals in the forcing anomalies drive warming of the upper ocean and increasing SSH, with the effect of the deep upwelling leading the CEC.
Effects of the hydraulic conductivity microstructure on macrodispersivity
Authors: Di Dato Mariaines , de Barros Felipe P. J. , Fiori Aldo , Bellin Alberto
Published: August 2016

Heterogeneity of the hydraulic properties is one of the main causes of the seemingly random distribution of solute concentration observed in contaminated aquifers, with macrodispersivity providing a global measure of spreading. Earlier studies on transport of solutes in heterogeneous formations, either theoretical or numerical, expressed dispersivity as a function of the geostatistical properties of the hydraulic conductivity K. In most cases, K follows a second‐order statistical characterization, which may not be adequate when heterogeneity is high. In this work, we adopt the Multi‐Indicator Model–Self Consistent Approach (MIMSCA) to compute the longitudinal and transverse macrodispersivity. This methodology enables to model the K field by using geological inclusions of different shapes and orientation (defined here as the microstructure), while replicating the heterogeneous macrostructure obtained by the second‐order statistics. The above scheme attempts to reproduce the effect on macrodispersion of different distribution and orientation of local facies, and for instance it may represent the orientation and spatial features of the layers that are often observed in aquifers. The relevant impact of the microstructure on effective conductivity, longitudinal and transverse macrodispersivities is analyzed and discussed, for both binary and lognormally distributed K fields.
Purification and characterization of an extracellular β‐glucosidase from Sporothrix schenckii
Authors: Hernández‐Guzmán Alicia , Flores‐Martínez Alberto , Ponce‐Noyola Patricia , Villagómez‐Castro Julio C.
Published: August 2016

An extracellular β‐glucosidase (E.C. 3.2.1.21), induced by cellulose in the mycelial form of human pathogen fungus Sporothrix schenckii, was purified to homogeneity using hydroxyapatite (HAp) adsorption chromatography in batch and Sephacryl S200‐HR size exclusion chromatography. The molecular mass of the purified enzyme was estimated to be 197 kDa by size exclusion chromatography with a subunit of 96.8 kDa determined by SDS/PAGE. The β‐glucosidase exhibited optimum catalytic activity at pH 5.5/45 °C and was relatively stable for up to 24 h at 45 °C. Isoelectric focusing displayed an enzyme with a pI value of 4.0. Its activity was inhibited by Fe2+ but not by any other ions or chelating agents. Km and Vmax values of the purified enzyme were 0.012 mm and 2.56 nmol·min−1·mg−1, respectively, using 4‐methylumbelliferyl β‐D‐glucopyranoside (4‐MUG) as the substrate and 44.14 mm and 22.49 nmol·min−1·mg−1 when p‐nitrophenyl β‐D‐glucopyranoside (p‐NPG) was used. The purified β‐glucosidase was active against cellobioside, laminarin, 4‐MUG, and p‐NPG and slightly active against 4‐methylumbelliferyl β‐D‐cellobioside and p‐nitrophenyl β‐D‐cellobioside but did not hydrolyze 4‐methylumbelliferyl β‐D‐xyloside, 4‐methylumbelliferyl β‐D‐galactopyranoside nor 4‐methylumbelliferyl α‐D‐glucopyranoside. In addition, the enzyme showed transglycosylation activity when it was incubated along with different oligosaccharides. Whether the transglycosylation and cellulase activities function in vivo as a mechanism involved in the degradation of cellulolytic biomass in the saprophytic stage of S. schenckii remains to be determined.
Paradoxical delay of senescence upon depletion of BRCA2 in telomerase‐deficient worms
Authors: Kwon Mi‐Sun , Min Jaewon , Jeon Hee‐Yeon , Hwang Kwangwoo , Kim Chuna , Lee Junho , Joung Je‐Gun , Park Woong‐Yang , Lee Hyunsook
Published: August 2016

BRCA2 is a multifunctional tumor suppressor involved in homologous recombination (HR), mitotic checkpoint regulation, and telomere homeostasis. Absence of Brca2 in mice results in progressive shortening of telomeres and senescence, yet cells are prone to neoplastic transformation with elongated telomeres, suggesting that BRCA2 has positive and negative effects on telomere length regulation along the path to tumorigenesis. Using Caenorhabditis elegans as a model, we show here that depletion of BRC‐2, an ortholog of BRCA2, paradoxically delays senescence in telomerase‐deficient mutant worms. Telomerase‐deficient worms (trt‐1) exhibit early replication senescence due to short telomeres. It should be noted that worms mutated in brc‐2 are not viable as well due to massive genotoxic insults. However, when BRC‐2 is depleted by RNA interference in trt‐1 mutant worms, the number of generations is unexpectedly increased with telomere length maintained, compared to telomerase mutants. Interestingly, depletion of other HR genes such as rad‐51 and rad‐54 exhibited similar effects. In worms doubly deficient of telomerase and brc‐2, rad‐51, or rad‐54, extra telomeric C‐circles were generated, suggesting that abrogation of HR induces an alteration in telomere environment favorable to illegitimate telomere maintenance when telomerase is absent. Collectively, absence of BRC‐2 in telomerase‐deficient background first leads to telomere shortening, followed by an induction of an as‐yet‐unknown telomere maintenance pathway, resulting in delay of senescence. The results have implications in the understanding of dysfunctional BRCA2‐associated tumorigenesis.
Meter Data Collection, Management, and Analysis
Authors: Wolf Tim
Published: August 2016

With their ability to provide ubiquitous measurement, monitoring, communication and control capabilities, smart meters are much more than the utility's cash register. They are, in effect, sensors for the distribution network, providing critical data and insight to improve grid reliability and efficiency in an age of rapidly expanding distributed energy resources and load volatility. This chapter provides readers with an overview of smart metering technology, insight into its architecture and evolving capabilities, and how utilities are collecting, managing and applying smart meter data to improve grid operations and deliver new programs and services to their customers.
Role of Renewable Energy
Authors: Wang Weisheng , Chen Ziyu , Zha Hao
Published: August 2016

Renewable energies have different characteristics comparing to fossil energy, such as wind and solar energies. With the rapidly increasing proportion of renewable power, the consequent impacts on smart grids cannot be neglected. In order to ensure successful operation of smart grids with high renewable energy penetration, advance technologies have been developed. This chapter first addresses basic principles and characteristics of renewable power generation, then impacts of renewable energy on smart grids and specific technologies are further introduced.
Role of Energy Storage
Authors: Hu Xuehao
Published: August 2016

In recent years, with increasing renewable power generation integrated into power grids, especially wind and solar power generation, various electric energy storage (EES) technologies, such as battery energy storage, have achieved fast development. The role of EES in the power system is important. The application of EES in the power system spans generation, transmission, distribution, and customer side of operations. There is a variety of energy storage technologies with different characteristics, which can be categorized as mechanical, electrical, electrochemical, thermal, and chemical energy storage. For application, it is necessary to select suitable energy storage technologies, considering not only a comparison of their comprehensive performance but also how they can work in combination with conventional means in power grids. Although the various EES technologies are maturing at different paces, all of them are making progress. EES has wide market potential and will greatly benefit the integration of renewable power generation and the stable operation of smart grids.
Evolution of Power Grids (Transmission)
Authors: Overholt Philip N. , Eto Joseph H.
Published: August 2016

Today's electric power transmission grid is the result of years of technological innovation driven by the needs of the institutions that have planned, built, operated, and regulated the grid. To understand how smart grid technologies – monitoring, communication, and control devices and systems – will influence the grid's future evolution, we must understand how the institutions and regulations that influence the grid have evolved and the challenges they currently face. This chapter illustrates the relationship between transmission grid evolution and the future of smart grid technologies by describing how synchrophasors – a leading example of smart grid technologies – will contribute to the continuing evolution of the US transmission system by maintaining and improving transmission system reliability, allowing for increased utilization of existing transmission lines and thereby delaying or avoiding the need for construction of new transmission facilities, and improving the operation of wholesale electricity markets.
Definitions, Scope, Visions, and Benefits
Authors: Widergren Steven E. , Pratt Robert G.
Published: August 2016

The term
smart grid
evokes different images to different people. Its scope spans the large‐scale production of electricity, the coordination of its delivery over great distances and local distribution systems into the end‐use facilities, and the application, storage, and production of electricity within these facilities. It touches a broad‐base of stakeholders that includes owners, operators, technology, and service providers from all segments of the system, as well as local, state, and federal government agencies that regulate electricity. At its core, smart grid represents the transformational application of information and communications technology to a more efficient and effective electric system. The vision of how this system will look and operate 5, 10, or 30 years from now gives birth to creative opportunities, which promise to yield great benefits economically, socially, and environmentally. This chapter discusses the meaning of smart grid, the extent of its transformational aspects to the electric grid, and the benefits its proponents hope to achieve as the future unfolds.
Global Survey of Smart Grid Activities
Authors: Biviji Mustafa A. , Martini Luciano , Nigris Michele De , Kang Dong‐Joo , Ton Dan
Published: August 2016

A survey of global smart grid activities provides trends prevalent in the electric industry across different geographies. These trends are either dictated by local/regional electric grid enhancement requirements or influenced by state or national policy goals. The International Smart Grid Action Network, a Clean Energy Ministerial initiative, conducts biennial survey to identify the key smart grid drivers and technologies trending worldwide. This chapter describes the key trends by geography as well as pioneering projects in seven smart grid application areas (smart metering, smart network management, integration of distributed energy resources, integration of large‐scale renewable energy sources/systems, aggregation [demand response, virtual power plant], smart customer and smart home, and electric vehicles and Vehicle2Grid applications) for the three major continents – North America, Europe, and Asia.
Behavioral Aspects of Smart Meters
Authors: Baddeley Michelle
Published: August 2016

This chapter outlines some of the economic and behavioral considerations that affect the use and uptake of smart metering technologies. In standard economic terms, smart meters (SMs) have the potential to enable better matching of supply and demand, enabling real‐time and more efficient pricing. They also have additional benefits explicable using key insights from behavioral economics. If SMs are designed to take account of common heuristics, that is, quick decision‐making rules, and decision‐making biases, then their net benefit will be significantly increased. The behavioral factors that are likely to be most significant for SMs include status quo and familiarity biases, anchoring and adjustment around reference points, social influences, and present bias/short‐termism. This chapter explores the potential for SMs to effectively enable household energy saving – for example, by providing a tool for setting default options, allowing more frequent and accurate real‐time energy use data for householders, conveying social information and/or improving information flows, and enabling householders to switch suppliers more easily. SMs have the potential to offer new services in the future too, for example – reducing fuel poverty by enabling prepayment customers to manage their energy payments more easily.
Wide Area Monitoring through Synchrophasor Measurement
Authors: Liu Yilu , Liu Yong , Zhang Ye , Guo Jiahui , Zhou Dao
Published: August 2016

Considered as one of the most significant developments of smart grid technology, wide area monitoring system (WAMS) utilizing synchrophasor measurements has been expected to help create a more reliable and efficient electric power infrastructure. The use of phasor measurement units (PMUs) can help with understanding, predicting, or even controlling the status of power grid stability in real time. A power system frequency monitoring network (FNET/GridEye) was first proposed in 2001 and then established in 2004. As a pioneering WAMS, it serves the entire North American power grid and other main power grids worldwide through advanced real‐time situational awareness techniques, such as real‐time measurement visualization, accurate disturbance location estimation, and interarea oscillation modal analysis. Furthermore, taking advantage of the vast historical database, postevent analysis, measurement‐aided model validation, and other nonreal‐time applications have also been investigated. Dozens of papers published in the past 10 years had discussed the FNET/GridEye's various functionalities. This chapter summarizes the FNET/GridEye work and presents some of the latest implementations of FNET/GridEye's applications.
Remedial Action Schemes and Defense Systems
Authors: Zhang Yichen , Raoufat Mohammad Ehsan , Tomsovic Kevin
Published: August 2016

The power system must be operated to withstand any single equipment outage as well as other credible contingencies. At times, this is either not possible or requires overly conservative operation of the system. In response, utilities have developed numerous specialized actions in response to specific events that ensures continued reliable operation of the grid. Such a defined response is generally referred to as a Remedial Action Scheme RAS). RAS have proliferated in recent years as they may allow deferred transmission upgrades and new interconnections. This chapter overviews various approaches to RAS design and related defense systems.
Defining, Measuring, and Improving Resilience of Electric Power Systems
Authors: Guttromson Ross , Watson Jean‐Paul
Published: August 2016

There is an emergence of interest in the area of power grid resilience; however, there is not a common definition of what it means, what metrics should be used, or how it should be differentiated from existing NERC (National Energy Reliability Council) and state‐based reliability definitions. This chapter provides a definition of resilience and associated metrics that can be used to quantitatively describe consequences to a high‐impact threat or group of threats. A methodology is then presented, which can be used to improve system resilience through the optimal selection of infrastructure investments or operating changes subject to various constraints, including financial.
Overview of Distributed Energy Resources
Authors: Hatziargyriou Nikos D. , Zountouridou Erietta I. , Vassilakis Athanasios , Moutis Panayiotis , Papadimitriou Christina N. , Anastasiadis Anestis G.
Published: August 2016

According to CIGRE Working Group 37‐23, distributed generators (DGs) are definedas nonpredictable, nondispatchable small generation units (nominal power below 50 MW), connected to distribution power systems. Although this definition is today challenged by the significant advances in forecasting techniques and the control capabilities offered by the power electronics interfacing most DGs to the distribution network, these are widely understood to include most renewable energy sources (except large hydro plants over 50 MW) and small CHP (combined heat and power) and fuel‐based (gas, diesel, biofuels) units. Distributed energy resources (DER) is a wider term that includes next to DG, distributed storage devices and flexible loads.

DER may produce AC or DC power and most of them need to be power conditioned via several stages, before they can be integrated to the grid. Nowadays, the great development in power electronics permit the safe and economic integration of DER to the passive distribution grids of the present, while it gives them the potential to be a key element of the active grids of the future.

This chapter provides an overview of the most popular DER, including renewable energy sources and storage. The basic electrical power generation mechanism and technology for each DER is briefly described. The power electronic interfaces and their control, which constitute very important components of DER, are beyond the scope of this chapter and are only superficially discussed. For each technology, simplified equations and the procedure for creating a dynamic model for simulation studies is provided.
Renewable Energy Forecasting
Authors: Bessa Ricardo J. , Dowell Jethro , Pinson Pierre
Published: August 2016

Presently, in several countries, the wind and solar power capacity connected to the distribution network is increasing steadily. In parallel, the investment in smart grid technologies is growing, which will support the integration of renewable energy and represents an opportunity to develop advanced management functions. Forecasting is a key input for several management functions of distribution system operators (DSOs).

This chapter describes modeling approaches allowing to take advantage of the wealth of power measurements available in near real‐time in a smart grid context [e.g., smart meters and SCADA (supervisory control and data acquisition) system], in order to improve the quality of renewable energy forecasting in a computationally efficient manner. As a basis, the power generation vector is to be considered as a multivariate one, that is, by simultaneously focusing on all sites of interest, instead of trying to build and estimate models at every location, individually. Two real‐world test cases with wind and solar generation are used to show the improvement in accuracy from exploring distributed information in a probabilistic forecasting framework.
HVDCNetworks for Offshore Wind Power
Authors: Finney Steve , Xu Lie , Bell Keith
Published: August 2016

This chapter introduces some of the main concepts and challenges associated with the design and development of large offshore DC systems. Various engineering, regulatory, and economic issues associated with offshore networks are described. Different converter topologies, and offshore DC grid configurations and control strategies are discussed. System behaviour and protection requirement during faults on the DC grid are highlighted. Various design and operation of high‐voltage DC (HVDC) networks considering protection requirement and continuity of power supply are discussed. Cost and regulatory considerations for offshore HVDC system are also briefly introduced.
Cybersecurity ofSCADAwithin Substations
Authors: Hahn Adam , Sun Chih‐Che , Liu Chen‐Ching
Published: August 2016

The cybersecurity of modern substations is becoming increasingly important as they continue to integrate more digital control and communication technologies. This chapter will explore the cybersecurity threats to substations and will then discuss various mechanisms to protect them. The chapter will demonstrate how the security protections, such as encryption, authentication, access control, and intrusion detection, should be applied to substation systems. The chapter will then discuss the emerging cybersecurity requirements for both product vendors and utilities.
Conservation Voltage Reduction
Authors: de León Francisco , Diaz‐Aguiló Marc , Raza Ashhar
Published: August 2016

The chapter presents the fundamental concepts of conservation voltage reduction (CVR). Starting from a historical overview and ending with the numerical assessment of its economic impact, the chapter discusses the implementation methods of CVR, the potential energy savings, and possible problems with undervoltage violations. A large set of household appliances, commercial and residential lighting devices, air conditioners, and motors under different operating conditions were tested in the laboratory to develop ZIP coefficients models. The ZIP coefficients for individual pieces of equipment are tabulated in a manner suitable for use in power flow simulations. The application of CVR on radial and meshed distribution systems is presented. Network‐wide field verification of the power flow models versus voltage reduction tests gives great confidence on the results. It is shown that CVR in meshed distribution systems yields energy savings of 0.5% per each 1% voltage reduction and economic savings to the customers of 0.25% per 1% voltage reduction. This is achieved at virtually no expense for the utility owing to the stiff nature of meshed networks. Radial systems perform very differently from one another and the degree of success is very much dependent on the system configuration and the necessary investment.
PowerQuality
Authors: Milanović Jovica V.
Published: August 2016

This chapter starts by providing basic introduction to Power Quality and defines major drivers for increased interest in Power Quality in current and future power networks. Following this, Power Quality subdivision into different phenomena is given and each phenomenon defined. Equipment and process sensitivity to Power Quality disturbances is discussed next and the concept of Process Immunity Time introduced as a key parameter in determining the financial consequences of inadequate Power Quality. The financial losses due to Power Quality disturbances and methodology for development of optimal techno‐economic solutions for Power Quality mitigation are discussed next. The penultimate section is devoted to Power Quality monitoring, followed by brief summary of trends and directions for future academic and industrial work in the area of Power Quality. The discussion provided in this chapter is generic and applies to all networks irrespective of network design and geographical location.
Condition Monitoring and Asset Management in the Smart Grid
Authors: Bangalore Pramod , B. Tjernberg Lina
Published: August 2016

One of the main characteristics of a smart grid is the availability of large volumes of data, for example, gained from sensors. This data can be utilized as a tool to estimate the state of the system as a whole or any component within the system. In order to achieve actionable information from the variety of data that is available from smart grids, it is important to use the correct mathematical and signal processing tools. Furthermore, the future smart grid is expected to have high levels of reliability. This can be achieved by integrating the condition monitoring systems with maintenance management, wherein the focus is shifted from corrective maintenance to predictive condition‐based maintenance.

This chapter introduces the concept of reliability‐centered asset management (RCAM). The RCAM approach provides the possibility of both qualitative and quantitative analysis toward optimal maintenance strategy. Furthermore, various issues with condition monitoring in smart grids have been discussed along with some literature that suggest possible solutions for these issues. Finally, a detailed case study of a data‐based condition monitoring method based on artificial neural network is presented to demonstrate one of the many possibilities to use data from various measurement systems to reach actionable decisions.
Power Electronics for Flexible Distribution Networks
Authors: Green Tim C. , Frost Thomas , Junyent‐Ferré Adrià , Mitcheson Paul D.
Published: August 2016

Distribution network operators today face multiple challenges arising from the proliferation of distributed renewable generation, electric vehicle chargers, and further electrification of heating/cooling. These are known causes of multiple power quality and operational concerns that include under‐ or overvoltage conditions and greater ratios between peak and average demand. The business‐as‐usual approach to handle these concerns can be very costly and in some cases be impractical. Power electronics could be used to mitigate the aforementioned issues but to date have seen little use in distribution networks despite widespread use in industrial motor drives, as interfaces for renewable generation and within HVDC transmission. This chapter discusses how and where power electronic converters can play their part in meeting challenges in future distribution networks. It goes on to discuss the barriers to adoption of power electronics and how those barriers might be addressed in order to move the benefit–cost ratio to favor their use.
Communication Solutions for Distribution Systems
Authors: Kim Myongsoo
Published: August 2016

Various communication systems have been used in distribution systems according to their purpose and are being developed for new applications. There are many applications in distribution area and we will be able to see more in the near future. Because distribution systems have tons of components and the components are scattered, the systems are more complicated than transmission systems and its prestage systems. There is no perfect solution for communication in distribution systems, but the optimized solution may be suggested by reviewing communication requirements. Possible communication solutions will be introduced and suggested according to applications in distribution area in the standpoint of the utility.
Integration of Solar Photovoltaics
Authors: Zong Qing‐Chang , Romero‐Cadaval Enrique , Miñambres‐Marcos Víctor
Published: August 2016

The main issues related to the integration of photovoltaic systems into the grid will be presented and discussed in this chapter. In the context of smart grids, photovoltaic installations, as distributed energy resources connected in many case to the distribution grid, can do much more than just injecting energy into the grid as an active part of the distribution system and can implement the active functions required for meeting the requirements of the future grid.

This chapter will define the present and future context of connected photovoltaic systems and their role in the future smart grid. Later, the general operation of these installations will be discussed to identify the possibilities they could offer to future grid. The main operation problems when connected to the grid are identified next. Finally, smart grid integration will be discussed, mainly focused on ancillary services, as active control using energy storage systems, reactive power, or voltage control, avoiding harmonic propagation. Other basic functionalities such as their operation as virtual synchronous generators or the islanding detection will also be discussed.
Microgrids in Distribution
Authors: Hatziargyriou Nikos D. , Kleftakis Vasilis A. , Papadimitriou Christina N. , Messinis George M.
Published: August 2016

According to CIGRE WG C6.21Microgrids are electricity distribution systems containing loads and distributed energy resources (DERs) (such as distributed generators, storage devices, or controllable loads) that can be operated in a controlled, coordinated way either while connected to the main power network or while islanded. The different parts of the microgrid can be interconnected via an AC link forming AC microgrids or via a DC link forming DC microgrids. The notion of control is critical in the definition of microgrids. In fact, what differentiates microgrids from Distribution Grids with distributed energy sources and loads lies in the capabilities to manage and coordinate the available resources, so that they appear to the upstream network as a single coordinated unit. The developments in power electronics that are used for the interconnection of inverter‐based generation and storage units, such as photovoltaics and batteries, within microgrids have provided the possibility of incorporating advanced functionalities in the control of the distributed resources. Droop curves such as active power – frequency (P–f) and reactive power – voltage (Q–V), similar to the ones of traditional rotating machines and together with the capability of remotely controlling them, allow the application of advanced control strategies for microgrid operation. Advanced Information and Communications Technology (ICT) provides further opportunities for the application of intelligent techniques in microgrids decentralized control.

This chapter deals with microgrid control and operation, including both primary and secondary voltage and frequency control and optimal dispatch among the DERs. Centralized and decentralized approaches are discussed, and typical results are displayed, obtained from laboratory setups at the Electric Energy Systems Laboratory of the National Technical University of Athens.
Modern Energy Management Systems: Real‐Time Management of the Interconnected Electricity Grid
Authors: Giri Jay
Published: August 2016

The widespread availability of electricity has had a profound effect on societies worldwide. In fact, in 2002, electrification was selected by the US National Academy of Engineers as “the most significant engineering achievements of the last century.” The electricity supply chain or the power grid is one of the most complex machines in existence that is meant to work round the clock. It consists of millions of components that work together. The energy management system (EMS) was developed to manage electricity supply across the high‐voltage grid.

The EMS has evolved over many decades in a quest to maintain the integrity and successful 24/7 operation of the electric power grid. It is a real‐time, computer‐based solution and they have been deployed for decades at utility control centers. This chapter describes the history and evolution of the EMS from its digital genesis in the 1970s to the capabilities of today's modern EMS that are essential to manage the future grid.

Today's modern EMS has evolved into a vast, diverse conglomeration of monitoring devices and advanced computer and communications technology that measures power system field conditions every few seconds (moving toward subseconds) and automatically issues controls as needed. Operators are provided timely alerts and information to ensure prompt decisions can be made to ensure reliability of the grid.

Operational benefits of some innovative emerging subsecond technologies are described, such as fast synchronous phasor measurements and fast‐acting control devices. Challenges posed by the recent growth of renewable energy resources, distributed energy sources, microgrids, and customer demand‐side management are also addressed. Finally, successful practical implementations of a modern EMS are described along with some concluding thoughts and takeaways for the future.