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The use of thermal modelling to increase the permissible load-carrying capability of distribution system transformers is attracting increasing interest. Many reported approaches calculate the rating of transformers in real time in response to system conditions. In this study, an experiment to validate and tune the parameters of such a thermal model is described, and explained how the results have been used to inform the inclusion of model-based seasonal ‘enhanced’ ratings in the network planning process.

It has been argued that increasing transmission network capacity is vital to ensuring the full utilisation of renewables in Europe. The significant wind generation capacity proposed for the North Sea combined with high penetrations of other intermittent renewables across Europe has raised interest in different approaches to connecting offshore wind that might increase also interconnectivity between regions in a cost effective way. These analyses to assess a number of putative North Sea networks confirm that greater interconnection capacity between regions increases the utilisation of offshore wind energy, reducing curtailed wind energy by up to 9TWh in 2030 based on 61GW of installed capacity, and facilitating a reduction in annual generation costs of more than €0.5bn. However, at 2013 fuel and carbon prices, such additional network capacity allows cheaper high carbon generation to displace more expensive lower carbon plant, increasing coal generation by as much as 24TWh and thereby increasing CO2 emissions. The results are sensitive to the generation "merit order" and a sufficiently high price would yield up to 28% decrease emissions depending on the network case. It is inferred that carbon pricing may impact not only generation investment but also the benefits associated with network development.

In order to strengthen the onshore transmission network in many parts of the world, voltage-source current–high-voltage direct current (VSC–HVDC) will increasingly be utilized. The effect of the operating point of a VSC-HVDC link and the control strategies employed can substantially affect the electromechanical oscillatory behavior of the ac network as well as the dc-side dynamics. In order for the full, flexible capability of VSC-HVDC to be exploited, further study of the effects of these controllers and their interactions with ac system responses is necessary. This paper addresses this gap. Both modal analysis and transient stability analysis are used to highlight tradeoffs between candidate VSC-HVDC power controllers and to study the electromechanical performance of the integrated ac/dc model. Tests are carried out on both a generic two-area model and a large-scale realistic network with detailed ac generator and HVDC models.

This paper outlines possibilities for connecting 2.4 GW of power from two separate wind farms at Dogger Bank in the North Sea to the GB transmission system in Great Britain. Three options based on HVDC with Voltage Source Converters (VSC HVDC) are investigated: two separate point-to-point connections, a four-terminal multi-terminal network and a four-terminal network with the addition of an AC auxiliary cable between the two wind farms. Each option is investigated in terms of investment cost, controllability and reliability against expected fault scenarios. The paper concludes that a VSC-HVDC point-to-point connection is the cheapest option in terms of capital cost and has the additional advantage that it uses technology that is commercially available. However, while multi-terminal connections are more expensive to build it is found that they can offer significant advantages over point to point systems in terms of security of supply and so could offer better value for money overall. A multi-terminal option with an auxiliary AC connection between wind farms is found to be lower cost than a full multi-terminal DC grid option although the latter network would offer ability to operate at greater connection distances between substations.

This paper details a methodology for investigating the reliability of different offshore grid design options for the connection of offshore wind power to shore. The methodology uses a sequential Monte Carlo-based technique that enables the investigation of realistic offshore phenomena, such as the weather dependency of component repair times. A number of case studies are examined for the connection to shore of a cluster of far offshore wind farms and a cost benefit analysis is performed which compares the capital costs, electrical losses, and reliability of each. There is found to be a clear value in options that have inherent redundancy and alternative protection strategies, which avoid the use of expensive dc circuit breakers, that are shown to be potentially viable. It is also found that low probability, high impact faults, such as transmission branch failures, are a key driver behind overall grid reliability.

Galena from four REE-rich (Khibina, Sallanlatvi, Seblyavr, Vuoriyarvi) and REE-poor (Kovdor) carbonatites, as well as hydrothermal veins (Khibina) all from the Devonian Kola Alkaline Province of northwestern Russia was analysed for trace elements and Pb and S isotope compositions. Microprobe analyses show that the only detectable elements in galena are Bi and Ag and these vary from not detectable to 2.23 and not detectable to 0.43 wt.% respectively. Three distinct galena groups can be recognized using Bi and Ag contents, which differ from groupings based on Pb isotope data. The Pb isotope ratios show significant spread with 206Pb/204Pb ratios (16.79 to 18.99), 207Pb/204Pb (15.22 to 15.58) and 208Pb/204Pb ratios (36.75 to 38.62). A near-linear array in a 207Pb/204Pb vs.206Pb/204Pb ratio diagram is consistent with mixing between distinct mantle sources, one of which formed during a major differentiation event in the late Archaean or earlier. The S isotopic composition (δ34S) of galena from carbonatites is significantly lighter (–6.7 to –10.3% Canyon Diablo Troilite (CDT) from REE-rich Khibina, Seblyavr and Vuoriyarvi carbonatites, and – 3.2% CDT from REE-poor Kovdor carbonatites) than the mantle value of 0%. Although there is no correlation between S and any of the Pb isotope ratios, Bi and Ag abundances correlate negatively with δ34S values. The variations in the isotopic composition of Pb are attributed to partial melting of an isotopically heterogeneous mantle source, while those of δ34S (together with Bi and Ag abundances) are considered to be process driven. Although variation in Pb isotope values between complexes might reflect different degrees of interaction between carbonatitic melts and continental crust or metasomatized lithosphere, the published noble gas and C, O, Sr, Nd and Hf isotopic data suggest that the variable Pb isotope ratios are best attributed to isotopic differences preserved within a sub-lithospheric mantle source. Different Pb isotopic compositions of galena from the same complex are consistent with a model of magma replenishment by carbonatitic melts/fluids each marked by quite different Pb isotopic compositions.

Conventional approaches to forecasting of real-time thermal ratings (RTTRs) provide only single-point estimates with no indication of the size or distribution of possible errors. This paper describes weather-based methods to estimate probabilistic RTTR forecasts for overhead lines which can be used by a system operator within a chosen risk policy with respect to the probability of a rating being exceeded. Predictive centers of weather conditions are estimated as a sum of residuals predicted by a suitable auto-regressive model and temporal trends fitted by Fourier series. Conditional heteroscedasticity of the predictive distribution is modelled as a linear function of recent changes in residuals within one hour for air temperature and wind speed or concentration of recent wind direction observations within two hours. A technique of minimum continuous ranked probability score estimation is used to estimate predictive distributions. Numerous RTTRs for a particular span are generated by a combination of the Monte Carlo method where weather inputs are randomly sampled from the modelled predictive distributions at a particular future moment and a thermal model of overhead conductors. Kernel density estimation is then used to smooth and estimate the percentiles of RTTR forecasts which are then compared with actual ratings and discussed alongside practical issues around the use of RTTR forecasts.

This paper presents an investigation into the potential benefits of interconnecting adjacent 33 kV demand groups in the GB distribution network by presentation of two case studies. Results presented are, firstly, a comparison of load profiles of adjacent groups and, secondly, following application of a series of credible future scenarios, the potential reduction in loss of load and generation curtailment achievable from interconnection and the proportion of time for which interconnection would be utilised. It was found that there is significant dissimilarity between load profiles of the adjacent groups analysed and interconnection could be valuable for the future distribution system. The value of interconnection could be increased with the use of storage, though more analysis is needed to quantify the economic viability of this.

This paper proposes a new breed of high-voltage dc (HVDC) transmission systems based on a hybrid multilevel voltage source converter (VSC) with ac-side cascaded H-bridge cells. The proposed HVDC system offers the operational flexibility of VSC-based systems in terms of active and reactive power control, black-start capability, in addition to improved ac fault ride-through capability and the unique feature of current-limiting capability during dc side faults. Additionally, it offers features such as smaller footprint and a larger active and reactive power capability curve than existing VSC-based HVDC systems, including those using modular multilevel converters. To illustrate the feasibility of the proposed HVDC system, this paper assesses its dynamic performance during steady-state and network alterations, including its response to ac and dc side faults.

In this paper we examine potential improvements in how load and generation forecast uncertainty is captured when setting reserve levels in power systems with significant renewable generation penetration and discuss the merit of proposed new methods in this area. One important difference between methods is whether reserves are defined based on the marginal distribution of forecast errors, as calculated from historic data, or whether the conditional distribution, specific to the time at which reserves are being scheduled, is used. This paper is a review of published current practice in markets which are at the leading edge of this problem, summarizing their experiences, and aligning it with academic modeling work. We conclude that the ultimate goal for all markets expected to manage high levels of renewable generation should be a reserve setting mechanism which utilizes the best understanding of meteorological uncertainties combined with traditional models of uncertainty arising from forced outages.

This paper presents two methods for evaluating and optimizing the configuration of a distribution network. A new loss-optimization method is described which partitions, optimizes and then recombines the network topology to identify the lowest loss configurations available. A reliability evaluation method is presented which evaluates, on a load-by-load basis, the most effective restoration path and the associated time. In contrast to previously-reported methods, the operation of different types of switch is integrated into this approach, reducing dependency on pre-determined restoration times for each load each fault location. This provides a more accurate estimate of the outage durations through identification of the specific restoration method for each load under each fault condition. The optimization method applied is shown to be effective in identifying optimally-reliable network topologies. Significant benefits are shown to be available.

This paper aims to describe methods to determine short term probabilistic forecasts of weather conditions experienced at overhead lines (OHLs) in order to predict percentiles of dynamic line ratings of OHLs which can be used by a system operator within a chosen risk policy with respect to probability of a rating being exceeded. Predictive probability distributions of air temperature, wind speed and direction are assumed to be normal, truncated normal and von Mises respectively. Predictive centres are estimated as a sum of residuals predicted by a univariate auto-regressive model or a vector auto-regressive model and temporal trends fitted by a Fourier series. Conditional heteroscedasticity of the predictive distribution is modelled as a linear function of recent changes in residuals within one hour for air temperature and wind speed or concentration of recent wind direction observations within two hours. Parameters of the probabilistic models are determined to minimize the average value of continuous ranked probability score which is a summary indicator to assess performance of probabilistic models. The conditionally heteroscedastic models are shown to have appropriate sharpness and better calibration than the respective homoscedastic models.

There is growing recognition that decarbonisation of existing uses of electricity is only ‘part of the story’ and that closer attention needs to be given to demand for energy in heating or cooling and in transport, and to all the energy vectors and infrastructures that supply the end-use demand. In this respect, concepts such as ‘multi-energy systems’ (MES) have been put forward and are gaining increasing momentum, with the aim of identifying how multiple energy systems that have been traditionally operated, planned and regulated in independent silos can be integrated to improve their collective technical, economic, and environmental performance. This paper addresses the need for modelling of MES which is capable of assessing interactions between different sectors and the energy vectors they are concerned with, so as to bring out the benefits and potential unforeseen or undesired drawbacks arising from energy systems integration. Drivers for MES modelling and the needs of different users of models are discussed, along with some of the practicalities of such modelling, including the choices to be made in respect of spatial and temporal dimensions, what these models might be used to quantify, and how they may be framed mathematically. Examples of existing MES models and tools and their capabilities, as well as of studies in which such models have been used in the authors' own research, are provided to illustrate the general concepts discussed. Finally, challenges, opportunities and recommendations are summarised for the engagement of modellers in developing a new range of analytical capabilities that are needed to deal with the complexity of MES.

This paper presents a comparison of two forms of cable connection of a distant offshore wind farm to a transmission system: AC and HVDC. The requirements of relevant industry standards in Great Britain (GB) that drive a connection design and, hence, its costs are highlighted along with an analysis of the ways in which AC cable connections might be made to comply while facilitating the export of active power. Dynamic studies investigating responses to grid-side short-circuit faults show that, in the particular scenarios studied, an AC connection of a wind farm in place of a large synchronous generator is marginally detrimental while an HVDC connection is beneficial. A comparison of costs shows that the crossover distance at which HVDC is cheaper than AC for wind farms of different sizes occurs at longer distances than have hitherto commonly been assumed, and AC connections benefit from reactive compensation not only at the point of common coupling and wind farm end, but also at the connection midpoint.

This paper describes a study conducted to address the question of how much power transfer capacity should be provided on a meshed transmission system to maintain reliability of supply to consumers in the presence of wind generation. A simulation methodology is presented that includes modeling of the available wind generation in the longer term across a quite large area taking into account correlations in available power between different locations in that area. A description is given of the results obtained in characterization of the relationship between the peak load in an area, the total generation capacity in that area, the proportion of it that is wind generation, and how much transmission import capability- “interconnection reserve” -is required for a given reliability of supply. Finally, a number of issues faced by power system investment planners are discussed and pointers given to further work to enable transmission utilities to meet the challenges presented by policy makers in respect of development of wind power to meet renewable energy targets.

Cascading outages can cause large blackouts, and a variety of methods are emerging to study this challenging topic. The Task Force on Understanding, Prediction, Mitigation, and Restoration of Cascading Failures, under the IEEE PES Computer Analytical Methods Subcommittee (CAMS), seeks to consolidate and review the progress of the field towards methods and tools of assessing the risk of cascading failure. This paper discusses the challenges of cascading failure and summarizes a variety of state-of-the-art analysis and simulation methods, including analyzing observed data, and simulations relying on various probabilistic, deterministic, approximate, and heuristic approaches. Limitations to the interpretation and application of analytical results are highlighted, and directions and challenges for future developments are discussed.

The power industry in many parts of the industrialized world faces major challenges over the next two decades to renew ageing networks, accommodate new generation, especially renewables, and make grid operation “smarter”. This requires increasing numbers of professionals, but in many places, the industry faces great losses in personnel and experience as senior engineers retire. As a consequence, the industry needs to recruit a new generation of well-qualified electrical engineering graduates. This paper describes one particular initiative to attract school leavers into engineering and electric power engineering in particular: the U.K.'s “Power Academy”. The main features of the scheme and its success to date are described along with the new challenges and various issues that remain to be addressed. These include the need for “engineering leadership” and career progression for technical specialists. It is argued that companies' continued investment in schemes like the Power Academy is essential to meet the challenges faced by the power industry and to ensure a healthy future supply of professional engineers.

Scientific research to characterize the long-term wind energy resource is plentiful. However, if the impact of wind power on the electric power system is the goal of modeling, consideration must be given to diurnal and seasonal effects, as well as the correlation of wind speed between geographical areas. This paper provides such detail by modeling these effects explicitly, enabling accurate evaluations of wind power impact on future power systems to be carried out. This is increasingly important in the context of ambitious wind energy targets driven in the U.K., for example, by the requirement for 20% of Europe's energy to be met from renewable energy sources by 2020. Both univariate and multivariate auto-regressive models are presented here and it is shown how they can be applied to geographically dispersed wind speed data. These models are applied to suitably de-trended data. The accuracy of the models is assessed both by inspection of the residuals and by assessment of the forecasting accuracy of the models. Finally, it is shown how the models can be used to synthesize wind speed and thus wind power time series with the correct seasonal, diurnal, and spatial diversity characteristics.

Thirty-five S isotope analyses obtained from six carbonatite complexes from the Superior Province, Canadian Shield, ranging in age from 1,897 Ma to 1,093 Ma, have δ34SCDT values of between −4.5‰ and +3.4‰. Pyrrhotite, chalcopyrite and pyrite mineral separates were used. Each complex possesses its own distinct range and mean S isotope composition. The range for Schryburt Lake is: −4.5‰ to −3.4‰ ( mean = −3.9‰), for Big Beaver House: −3.6‰ to −1.5‰ (mean = −2.2‰), for Cargill: −1.5‰–+0.5‰ (mean = −0.7‰), for Spanish River: −0.1‰–+0.1‰ (mean = 0.0‰), and for Firesand River: +1.3‰–+3.4‰ (mean = +1.7‰). A single sample from Carb Lake yielded a δ34SCDT value of +2.8‰. Differences in isotope compositions can be related to isotope effects brought about during melt generation and emplacment, such as variations in fo2 and temperature. The different S and C isotope data for most complexes, however, suggest that the parental melts could have been generated from a heterogeneous mantle source, although process-driven changes cannot be completely ruled out.

This paper aims to describe methods to forecast wind speeds experienced around overhead lines (OHLs) in order to predict the wind cooling effect and thus the dynamic line ratings (DLRs) of OHLs. The wind speed at a particular OHL span is forecast through a kriging interpolation between the wind speed predictions produced by a vector auto-regressive (VAR) model for a limited number of weather stations at which observations have been obtained. A temporal de-trending method is used to ensure the stationarity of de-trended data from which model parameters are determined. A spatial de-trending method is adopted in a kriging model. The results show that the kriging model performs better than the inverse distance weighting (IDW) method and that the spatial de-trending makes the main contribution to the accuracy of interpolation. Furthermore, the VAR forecasting model is shown to give greater improvement over persistence than a simple auto-regressive (AR) model.

The increase of non-synchronous generation sources on a power network are changing the system dynamics and this can lead to problems with stability. One of the contributions to the change in system dynamics is the variation in system inertia. By approximating a traditional stability metric, the critical clearing time (CCT) in an energetic framework we conduct a parametric investigation of the effect of inertia on power system stability. A set of solid three phase to ground faults are considered on a small but not trivial power system, the two-machine infinite bus network. The performance of the approximated CCT is compared to the true CCT.

A background of increasing uncertainty in all time horizons of power system planning and operation has prompted the development of a comprehensive methodology and an advanced new practical tool for assessing both the static and dynamic security of a real network facing a large number of uncertainties. This paper describes this development, the steps of a study methodology and the incorporation of advanced security-constrained optimal power flow, dynamic simulation, statistical analysis tools and a specially developed set of sampling functions into a unique environment. The possible hardware set-ups are outlined and, finally, some examples of the tool's application are given.

The Turiy Massif, on the southern coast of the Kola Peninsula, consists of five intrusive complexes containing a variety of carbonatites, phoscorites, melilitolites, ijolites and pyroxenites. Petrographic and mineralogical studies of the different rocks show that the samples are texturally heterogeneous. Minerals including apatite, garnet, magnetite, melilite, mica and pyroxene, show systematic variations in composition relating to the rock type in which they occur. Compositional similarities and/or distinct trends are seen in the mineral compositions within the each of the pyroxenite-melilitolite, and melteigite-ijolite rock series, indicating linked petrogenetic histories within each of the two series. The carbonatites from the northern complex may be related to nearby melilitolites, but the central complex carbonatites and phosocorites do not bear any mineralogical (or isotopic) similarities to any of the silicate rocks within the massif.

This paper analyses the dynamic behaviour of a power system with both FACTS and VSC HVDC, in particular, possible potential interactions between a STATCOM and a VSC in a point-to-point HVDC link. The investigation considers different STATCOM locations and VSC control strategies. A generic linearized mathematic model is firstly developed, where a combined method involving relative gain array (RGA) and modal analysis is applied to identify the interactions within the plant model and the outer controllers. The interactions identified are further analysed by creating a set of scenarios integrating both the STATCOM and VSC HVDC into a dynamic equivalent realistic AC system. Results show a collaborative operation between the STATCOM and the closely located VSC with reasonably tuned controllers.

During high wind speed shutdown (HWSS) events, the power outputs of wind power plants may be subject to high ramp rates, causing issues for the System Operator (SO) in predicting total wind output, allocating adequate reserve levels and minimising balancing costs. As the timing of these events is difficult to predict, it is proposed that individual turbines may be used as probabilistic early warning indicators of HWSS events across sites, and by extension to a wide geographical area. The shut-down history of two separate wind farms across Scotland is analysed to determine the likelihood and impact of such events. It is shown that in most cases, HWSS does not result in the full loss of availability. Factors such as turbine elevation and mean wind exposure are key indicators of the order of shut-down across a site. The suggestion that sites could be used as early warning indicators for the pattern of HWSS across a transmission zone is difficult to characterise and for the two wind farms studied, prediction was not consistent.

Isotopic compositions of the noble gases (He, Ne, Ar, Kr, Xe) were obtained by stepwise heating of separated mineral phases from carbonatites from Brazil (Jacupiranga, Tapira) and Canada (Borden, Oka, and Prairie Lake) as well as one syenite (Poohbah Lake, Canada). Mineral phases used were apatite, forsterite, diopside, calcite, monticellite, and perovskite. Large amount of in situ produced 238U-fissiogenic 131–136Xe, along with lesser amounts of 238U-fissio-genic 83–86Kr and in situ 4He were found in most samples. An apatite sample from the Prairie Lake carbonatite showed a 136Xe130Xe ratio of about 1400. Some samples, mostly apatites, showed excess 129Xe relative to air in the high temperature (1800°C) gas fractions. The highest 129Xe130Xe ratios, between 7.0 and 8.6, are similar to those found in other mantle-derived materials such as MORBs and diamonds. The excess `Xe is considered to be primordial and attributed to now extinct nuclide 129I once present in the early history of the Earth. Neon isotopic compositions were also anomalous showing very low 20Ne22Ne ratios (down to 0.01) and high 21Ne22Ne ratios (up to 1.25). They are attributed to Wetherill reactions, such as 18O(α,n)21Ne, 19F(α,n)22Na(β+)22Ne, and so on. The measured 40Ar/36Ar ratios are extremely variable and range from values that are close to atmospheric to values as high as 42400. Stepwise heating studies of an apatite from the Jacupiranga carbonatite indicate that the high temperature fractions retain the original noble gas signature of the carbonatite source. The 40Ar/36Ar ratios for the high temperature gas fractions are about 6400 or smaller. A plot of 40Ar/36Ar vs. 129Xe/130Xe shows that the source of carbonatites is different and less degassed than that of MORBs. The presence of excess 129Xe in carbonatites suggests that carbon in carbonatites is unlikely to be recycled C related to subduction processes.

Major-, trace- and rare-earth-element data from ten natrocarbonatite lavas collected during the June 1993 extrusive activity define two distinct groups. Although both groups are characterized by low Nb and Zr contents, and low Th/U (~1.0); Ba/Sr>1.0; (La/Sm)N>40; high Ba, Mo, Sr, W contents; and LREE contents ~1000 to 2000×chondrite, one group has much higher Al2O3, Fe2O3, Nb, Pb, SiO2, Zr and total REEs contents. These differences are attributed to the presence of silicate spheroids in natrocarbonatites that form within the latter group. Similarity in trace- and rare-earth-element-normalized patterns for both groups of natrocarbonatite lavas suggest either a common source or generation from a common parental melt. Models proposed for the origin of natrocarbonatites include immiscible separation from a peralkaline, silicate magma, or late-stage fractionation from a parent olivine sovite magma. Although natrocarbonatite melt formation may be controlled by either of these differentiation processes, certain trace-element ratios for the 1993 lavas, such as Ce/Pb (~9), and Th/Nb (~0.1) are similar to those estimated for primitive mantle, and their Sm/Nd ratios (~0.07) are quite different to the average value of 0.15 for most carbonatites world-wide. The similarity in element ratios in many of the older silicate lavas at Oldoinyo Lengai (e.g., Zr/Nb, La/Nb, Ba/Nb, Rb/Nb, and Ba/La) to those estimated for HIMU and EM I suggest that source characteristics can be reflected in such melts. Even if the natrocarbonatites are formed by liquid immiscibility, recent experiments have shown that partition coefficients for trace elements (e.g., Ba, Ce, Mo, Nb, Pb, Th, U) between conjugate carbonate and silicate melts approach unity with increasing temperature. Alternatively, the similarity in trace-element ratios between those for the silicate lavas from Oldoinyo Lengai and mantle components are simply fortuitous.

This chapter describes the behaviour of power systems during faults and illustrates the requirements for power system protection. The components of protection systems and the typical schemes used to protect power systems are described. An overview of the future challenges relating to protection is provided, with specific comments relating to the impact of distributed generation on network protection systems.

This chapter describes the main technical limits that must be satisfied in the operation of T&D networks and how various system elements are controlled to ensure safe, continuous supply of electricity. Some discussion is given on the impact of renewable generation and the potential contribution of energy storage, along with some other developments that promise to provide greater flexibility to system operators.

We consider a microgrid for energy distribution, with a local consumer, a renewable generator (wind turbine) and a storage facility (battery), connected to the external grid via a transformer. We propose a 2 steps-ahead reinforcement learning algorithm to plan the battery scheduling, which plays a key role in the achievement of the consumer goals. The underlying framework is one of multi-criteria decision-making by an individual consumer who has the goals of increasing the utilization rate of the battery during high electricity demand (so as to decrease the electricity purchase from the external grid) and increasing the utilization rate of the wind turbine for local use (so as to increase the consumer independence from the external grid). Predictions of available wind power feed the reinforcement learning algorithm for selecting the optimal battery scheduling actions. The embedded learning mechanism allows to enhance the consumer knowledge about the optimal actions for battery scheduling under different time-dependent environmental conditions. The developed framework gives the capability to intelligent consumers to learn the stochastic environment and make use of the experience to select optimal energy management actions.

To integrate wind power into the electrical power system studies need to be made of its impact. Wind plants are stochastic in nature and this makes them differ from traditional plants. One method to model the stochastic nature of wind plants is to create a wind field model and simulate wind data that can then be used to determine power outputs. There are a large number of models available, however often these models are not adequately validated. This paper proposes a number of criteria that all wind field models should be validated against and the methods that can be used to do this.

This paper points to some ways in which concepts of ‘security’ might be revised in order to more cost-effectively accommodate new generation and wider market interactions without undue increase in system unreliability. The background to ‘security standards’ and the scope for change are discussed. A number of issues are cited that are likely to make the achievement of a theoretical ideal very difficult. It is concluded that, while new tools for estimating quantified risk should be very useful, the choices that must currently be made in modelling the power system and difficulties with obtaining good data mean that experience is required for their use and they do not negate the need for agreed ‘standards’.

This paper is a result of ongoing activity carried out by Understanding, Prediction, Mitigation and Restoration of Cascading Failures Task Force under IEEE Computer Analytical Methods Subcommittee (CAMS). The task force's previous papers [1, 2] are focused on general aspects of cascading outages such as understanding, prediction, prevention and restoration from cascading failures. This is the second of two new papers, which extend this previous work to summarize the state of the art in cascading failure risk analysis methodologies and modeling tools. The first paper reviews the state of the art in methodologies for performing risk assessment of potential cascading outages [3]. This paper describes the state of the art in cascading failure modeling tools, documenting the view of experts representing utilities, universities and consulting companies. The paper is intended to constitute a valid source of information and references about presently available tools that deal with prediction of cascading failure events. This effort involves reviewing published literature and other documentation from vendors, universities and research institutions. The assessment of cascading outages risk evaluation is in continuous evolution. Investigations to gain even better understanding and identification of cascading events are the subject of several research programs underway aimed at solving the complexity of these events that electrical utilities face today. Assessing the risk of cascading failure events in planning and operation for power transmission systems require adequate mathematical tools/software.

This paper is a result of ongoing activity carried out by Understanding, Prediction, Mitigation and Restoration of Cascading Failures Task Force under IEEE Computer Analytical Methods Subcommittee (CAMS). The task force's previous papers are focused on general aspects of cascading outages such as understanding, prediction, prevention and restoration from cascading failures. This is the first of two new papers, which extend this previous work to summarize the state of the art in cascading failure risk analysis methodologies and modeling tools. This paper is intended to be a reference document to summarize the state of the art in the methodologies for performing risk assessment of cascading outages caused by some initiating event(s). A risk assessment should cover the entire potential chain of cascades starting with the initiating event(s) and ending with some final condition(s). However, this is a difficult task and heuristic approaches and approximations have been suggested. This paper discusses different approaches to this and suggests directions for future development of methodologies. The second paper summarizes the state of the art in modeling tools for risk assessment of cascading outages.

The location and variability of wind generation along with the difficulty of gaining permits for the construction of new overhead lines are placing increasing pressure on transmission system operators to increase utilisation of existing transmission capacity in as flexible a way as possible. Phase sifting transformers (PSTs) can contribute to this. However, to gain maximum benefit, the settings of a number of PSTs should be coordinated in a ‘smart’ way. This paper presents an overview of PSTs, their technical characteristics and their current use on GB Transmission Network. Issues and challenges for their effective and coordinated operation are raised and discussed with examples from a test network.

In the scope of a recently launched European Research Project, a team of experts from public laboratories and TSO is in charge of defining the concepts and methodological approaches to design and analyse the technical and economic feasibility of future HVDC grids. This work aims at identifying, assessing and comparing several possible HVDC network topologies, with appropriate control and protection schemes, able to collect wind energy on large areas, transmit it at the best points to the AC grid and provide the necessary ancillary services for optimising the DC / AC interconnection in normal and disturbed conditions. The methodology adopted for the study and presented in this paper will focus on three main items: 1. identify and assess the economic drivers for the development of off-shore HVDC networks 2. identify the requirements for an optimal operation of the AC / DC interconnected power systems under normal and emergency conditions 3. conceptualise the coordinated control / command and protection plans for HVDC networks This paper gives a comprehensive view of the issues and tasks to be addressed during the run of the project.

This paper discusses the need for new test system models to be developed and made available to researchers. A number of features of such test systems are proposed. These include sufficient size and scope to allow control interactions to be studied but not so much that phenomena associated with new technologies cannot be understood. It is recalled that the performance of new technologies and their controls should be verified on a full system model that is as faithful to the real system and its parameters as possible and that this requires access to data often owned by generating companies to which system operators have access but do not feel able to disclose. Finally, arguments are presented as to why such data should be disclosed and it is recommended that regulatory authorities take steps to achieve it.

40 Ar/ 39 Ar total gas ages of muscovites and biotites from granites associated with NE Kibaran belt (Karagwe-Ankolean) in NW Tanzanian are in the range of about 945-700 Ma, much less than the estimated age of the granites. Age gradients in the muscovite spectra are indicative of partial gas loss as a result of thermal overprinting. Evidence for at least two tectonothermal events, at ca. 950 Ma and ca. 700 Ma, is noted. The older of these correlates with the formation of tin-bearing pegmatites and hydrothermal veins in the Kibaran belt; the younger with vein emplacements in the Burundian and/or a deformational episode. Correlation of 40 Ar/ 39 Ar age data with K-Ar and Rb-Sr data from other parts of the Kibaran belt in Burundi, Rwanda and Zaire indicates that the NE Kibaran belt, east of the Western Rift, experienced a tectonothermal history similar to that of the western part of the during the late-Proterozoic.

The Great Abitibi Dyke (GAD) which can be traced northeast, for > 700 km, across the Abitibi Belt in the southeastern Superior Province of the Canadian Shield, is composed of olivine gabbro to monzodiorite, weakly saturated to undersaturate d in silica. All rocks of the GAD can be derived by mainly plagioclase and olivine fractionation from a parental magma corresponding in composition to chilled margin samples. Two units can be distinguished , a marginal unit (Unit 1) representing 0-50% crystallization and a central unit (Unit 2\ found over about half of the dyke length, representing 50-70% crystallization. Modelling, using Pearce elemental ratio analysis, quantifies the fractionation history and allows mass-balance calculations over the present exposure level of the dyke. The approximate balance between the amounts of cumulate and fractionated rocks suggests that Unit 1 differentiated essentially in situ as a closed system. In contrast, Unit 2 rocks were formed by loss of substantial plagioclase and olivine from the parental magma. This fractionate must have either been lost to depth or left behind in an external chamber. Unit 2 rocks show depletion in plagioclase and enrichment in mafic minerals along strike towards the southwest (deeper exposure level?), a trend explained by density stratification. Regional variation in Unit 1 chemistry is interpreted in terms of lateral magma injection towards the northeast from the locus of Keweenawan rift volcanism. Feldspar, olivine, and augite compositions are linearly correlated with equilibrium temperature and extent of magma evolution. The parent magma had a trace element chemistry corresponding to a 'within-plate' setting and was probably derived from an incompatible-element enriched mantle similar to the source for ocean island basalts (OIBs).

The power industry in the UK faces major challenges over the next two decades to renew ageing networks and accommodate new generation, especially renewables. As a consequence, the industry needs to recruit a new generation of well-qualified electrical engineering graduates. This paper describes the IET Power Academy, established in 2004 to attract engineering graduates into employment within the power industry. In 2008, 17 companies and 7 leading UK universities are collaborating in the scheme with over 60 scholarships being offered each year. The scholarship package includes a bursary, a contribution to university fees, paid vacation training and an annual seminar. The scheme can be judged to have been a success to date, though challenges still remain, including persuading greater numbers of school and college leavers to study electrical or electronic engineering at university. As time goes on, while the industry can expect to have largely addressed issues associated with graduate recruitment, mid-career support and retention is likely to emerge as a key concern.

In the last decade, the interest in and development of distributed generation (DG) in the UK has increased considerably. Large penetrations of DG are threatening network integrity, and resulting pressures on voltage levels, power flows and fault levels are risking security and quality of supply. Cost of network reinforcement and substation equipment upgrades will be passed on to generators and DG connections will become more uneconomic as time progresses. Consequently, distribution networks must evolve from their traditional passive role to actively managed systems if they are to accommodate these connections and their inherent issues whilst remaining economically viable. Increased levels of actively managed DG and associated network automation will affect control room operational activities by increasing the amount and diversity of information that must be processed and control action that must be subsequently executed. This paper will discuss possible future network conditions and the effects on control room operations, whilst exploring promising solutions to support control engineers in managing these new control room drivers.

Magmato-hydrothermal cassiterite-topaz ore at the Carboniferous East Kemptville (EK) greisenhosted tin deposit (Nova Scotia, Canada) is cross-cut by veins containing apatite, triplite, vivianite and fluorite. Initial 87Sr/86Sr ratios of these minerals have an extreme range (0.7135 to 0.8284). The initial ratios of the host rocks, EK quartz-topaz rock and Davis Lake biotite monzogranite (0.729±0.001, 0.727±0.004), are also high. The adjacent Meguma Group metasedimentary rocks are more typical of crustal material (0.712–0.719 at 330 Ma). Rb and Sr contents of EK fluorite (max.: 13.0, 1420 ppm) and apatite (max.: 88.1, 6660 ppm) are unusually high and variable. Unexpectedly, high Sr contents correlate positively with the high initial 87Sr/86Sr ratios. Fluorite and phosphate minerals from the first set of post-greisen veins at East Kemptville reflect the unusual chemistry of a high 87Sr/86Sr fluid present in the deposit after ore formation. The most extreme composition of this fluid was characterized by 87Sr/86Sr>0.8284, high Rb/Sr, high P, Rb, Cu, Zn and Fe contents, but low abundances of Ca, Pb and Sn with respect to the Davis Lake monzogranite. Such a fluid could have been derived from the greisen fluid and modified by reaction with the overlying Meguma metawacke. A second alternative, which cannot be well constrained at present, is that an extremely radiogenic fluid entered the deposit after ore formation and mixed with the postore fluid. In either case, the modified fluid subsequently mixed with meteoric water and precipitated the minerals with much lower 87Sr/86Sr ratios and Rb and Sr contents.

The growing role of wind power in power systems has motivated R&D on methodologies to characterise the wind resource at sites for which no wind speed data is available, Applications such as feasibility assessment of prospective installations and system integration analysis of future scenarios, amongst others, can greatly benefit from such methodologies. This paper focuses on the inference of wind speeds for such potential sites using a Bayesian approach to characterise the spatial distribution of the resource. To test the approach, one year of wind speed data from four weather stations was modelled and used to derive inferences for a fifth site. The methodology used is described together with the model employed and simulation results are presented and compared to the data available for the fifth site. The results obtained indicate that Bayesian inference can be a useful tool in spatial characterisation of wind.

A background of increasing uncertainties in all time horizons of power system planning and operation has prompted the development of a comprehensive methodology and an advanced new practical tool for assessing both the static and dynamic security of a real network facing a large number of uncertainties. This paper briefly describes the methodology and then focuses on a study carried out during year 2003, leading to determine total transfer capacities on some French borders.

International audience; The eastern part of the agpaitic Khibina complex is characterized by the occurrence of dykes of various alkali silicate rocks and carbonatites. Of these, picrite, monchiquite, nephelinite and phonolite have been studied here. Whole rock and mineral geochemical data indicate that monchiquites evolved from a picritic primary magma by olivineþ magnetite fractionation and subsequent steps involving magma mixing at crustal levels. None of these processes or assimilation=magma mixing of wall rocks or other plutonic rocks within the complex can entirely explain the geochemical and Nd-Sr-isotopiccharacteristics of the monchiquites (i.e. a covariant alignment between (87Sr/86Sr)370 0.70367, (143Nd/144Nd)3700.51237 and (87Sr/86Sr)3700.70400, (143Nd/144Nd)370 0.51225 representing the end points of the array). This signature points to isotopic heterogeneities of the mantle source of the dyke-producing magma. The four mantle components (i.e. depleted mantle, lower mantle plume component, EMI-like component and EMII-like component) must occur in different proportions on a small scale in order to explain the isotopic variations of the dyke rocks. The EMII-like component might be incorporated into the source area of the primary magma by carbonatitic fluids involving subducted crustal material. The most likely model to explain the small-scale isotopic heterogeneity is plume activity. The results of this study do not provide any support to a cogenetic origin (e.g. fractionation or liquid immiscibility) for carbonatite and monchiquite or other alkali-silicate dyke rocks occurring in spatial proximity. Instead, we propose that both, carbonatite and picrite=monchiquite, originated by low-degree partial melting of peridotite. Textural observations, mineralogical data, and C and O isotopic compositions suggest incorporation of calcite from carbonatite in monchiquite and the occurrence of late-stage carbothermal fluids.

This paper uses a newly developed sensitivity analysis based security constrained optimal power flow (SASCOPF) to calculate the optimal amount of VAr support that needs to be committed while fully exploiting the available control capabilities of the system. The optimal portfolio of reactive contracts to be accepted should be adequate to maintain system security and quality of supply across a number of loading conditions while taking into account credible contingences.

Power systems are operated with some margin of security to ensure that the most likely losses of plant will not cause interruptions to supply. However, this security margin has a cost that may not be justified by the benefit in terms of prevention of lost load. The authors argue that the level of security could be set on the basis of a cost/benefit analysis that balances the cost of operating the system against the expected outage cost. The expected outage cost is determined using a Monte Carlo simulation of the system operation in which random outages are simulated. Such a simulation should not be limited to small but relatively frequent outages but should also include major disturbances that affect a large part of the system. In order to achieve a sufficient degree of accuracy, the simulation models the actions taken to save the system during emergencies, the duration of the restoration process, and possible protection malfunctions. It is shown that sympathetic trippings due to protection malfunction can have a very significant impact on the probability of major incidents and hence on the value of security.

Applications for the connection of large-scale wind power generation to transmission networks are presenting new issues both for transmission system planners and generation developers. One of the major problems faced is the assessment of transmission system capacity requirements for the export of power from areas with high penetration of variable and intermittent sources of generation such as wind power. A method for evaluating the required transmission connection capacity from an area dominated by wind generation to the main interconnected system is presented, based on historical time series data for both wind power generation output and the demand in the group. The operational implications for the transmission system and generation owners are evaluated using a cost-benefit approach. The method is demonstrated for a number of network situations. Conclusions are drawn about the value of the method and, more generally, about the trade-off between investment in transmission capacity and curtailment of wind generation under favourable wind conditions.