Assessing the value of increasing GB interconnection

The liberalisation of electricity markets and increasing penetration of renewable generation are encouraging trading opportunities to be identified and developed. In Europe, the importance of interconnection is well recognised. Interconnections are particularly important for islanded nations, like Great Britain, which provides access to generation and demand across the national boundaries via sub-sea HVDC cables while providing means to share reserves enhancing the security of supply and reducing overall costs. There are plans in place to significantly increase the current 5 GW of interconnection capacity between GB and neighbouring European countries. The paper investigates the expected impacts that a large increase in interconnection capacity could have on key electricity market parameters such as marginal prices, carbon emissions and the nature of utilisation of existing and future GB interconnections. Several scenarios have been considered to model future uncertainty for the years 2020 and 2025

A Reliability Evaluation of Offshore HVDC Transmission Network Options

There are ambitious targets in place for the development of large amounts of offshore renewable energy in the coming years. The offshore wind sector is expected to provide the vast majority of the projected growth which means large scale and far from shore projects are likely to become common. The transmission distances involved suggest HVDC technology is likely to be deployed and analysis to date has suggested there will be value in delivering co-ordinated offshore grids as opposed to simpler radial connection to shore. However, there are numerous technology and design options available for the delivery of offshore HVDC networks and, given the offshore climate can makes access for component maintenance or repair challenging, the reliability performance of different options is an important factor which has not been explored in much of the existing literature. This thesis details a novel methodology for investigating the reliability of different offshore grid design options for the connection of offshore wind power to shore or the interconnection of regions. A sequential Monte Carlo simulation methodology is used that allows investigation of realistic offshore phenomena such as the weather dependency of component repair times. A number of case studies are examined and a full cost benefit analysis is performed which compares the capital and operational costs, electrical losses and reliability performance of each grid option. There is shown to be clear value in options that include a degree of inherent redundancy and it is also shown that alternative protection strategies which avoid the use of expensive DC circuit breakers are potentially viable at lower cost and little expense to performance. An investigation of the key drivers behind overall offshore grid reliability is also made and it is found that low probability, high impact faults such as transmission branch failures have the greatest influence

Metrics for determining the frequency stability Limits of a power system : a GB case study

The changing power landscape introduces concerns about frequency management in a power system with significant amounts of non-synchronous sources of power. In islanded power systems like Great Britain and Ireland, electricity system operators are sometimes forced to undertake very expensive redispatch actions, including curtailing large amounts of renewable generation to meet statutory frequency stability constraints. Consequently, there is an imminent need to understand and quantify the limits that these constraints pose on the power system and develop metrics that can be easily integrated into current system planning and operational paradigm. This paper analyses three such metrics for quantifying the containment limits of a power system at a given operating point. The paper argues that while the penetration of non-synchronous dispatch can indeed be used as the basis of a metric to define the containment limits of a power system, it does not account for variations in the contributions of other containment factors such as inertia. To address the aforementioned issue two alternatives are proposed: the first defines the containment limits of a power system without direct reference to penetration of non-synchronous power, instead it determines a relationship in terms of critical inertia. The second alternative improves upon the first and it considers the components of frequency stability constraints, offering an increased degree of flexibility in quantifying containment limits, and understanding the influence that certain key factors have on frequency containment

The impact of reduced system inertia on system planning and HVDC interconnection

Over the past decade, significant levels of wind and solar generation have been built in Great Britain (GB). These represent non-synchronous sources of power with little or no contribution to system inertia. Further such developments are expected along with increases in HVDC interconnection capacity with mainland Europe. This paper presents a modelling framework to study the economic impact of operating a low inertia system. It is used to study a range of scenarios for the years 2020 and 2025 and provides an assessment of economic impacts of increasing GB interconnection for two sets of limits to the rate of change of frequency (RoCoF) that would arise after a loss of infeed event. The study shows that savings of between £44 million and £247 million in 2020 and up to £539 million in 2025 can be made by increasing the maximum RoCoF settings from 0.125 Hz/s to 0.5 Hz/s and the volume of curtailment of operation of renewables and interconnector imports is much reduced

A reliability evaluation of offshore HVDC grid configuration options

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 allows 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 shown to be clear value in options that have inherent redundancy and alternative protection strategies which avoid the use of expensive DC circuit breakers 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

HVDC transmission : technology review, market trends and future outlook

HVDC systems are playing an increasingly significant role in energy transmission due to their technical and economic superiority over HVAC systems for long distance transmission. HVDC is preferable beyond 300–800 km for overhead point-to-point transmission projects and for the cable based interconnection or the grid integration of remote offshore wind farms beyond 50–100 km. Several HVDC review papers exist in literature but often focus on specific geographic locations or system components. In contrast, this paper presents a detailed, up-to-date, analysis and assessment of HVDC transmission systems on a global scale, targeting expert and general audience alike. The paper covers the following aspects: technical and economic comparison of HVAC and HVDC systems; investigation of international HVDC market size, conditions, geographic sparsity of the technology adoption, as well as the main suppliers landscape; and high-level comparisons and analysis of HVDC system components such as Voltage Source Converters (VSCs) and Line Commutated Converters (LCCs), etc. The presented analysis are supported by practical case studies from existing projects in an effort to reveal the complex technical and economic considerations, factors and rationale involved in the evaluation and selection of transmission system technology for a given project. The contemporary operational challenges such as the ownership of Multi-Terminal DC (MTDC) networks are also discussed. Subsequently, the required development factors, both technically and regulatory, for proper MTDC networks operation are highlighted, including a future outlook of different HVDC system components. Collectively, the role of HVDC transmission in achieving national renewable energy targets in light of the Paris agreement commitments is highlighted with relevant examples of potential HVDC corridors

The impact of interconnectors on the GB electricity sector and European carbon emissions

A model of the European electricity system is used to analyse the impact of increasing interconnection levels between Great Britain and its European neighbours. Scenarios are assessed for 2020, 2025 and 2030. Several policy questions are highlighted around the assessment criteria for approving interconnector projects and the viability of existing investment and remuneration models. Results show that a GB specific carbon tax in 2020 contributes to a relatively high cost of energy and therefore high imports into GB. Increasing GB interconnection capacity in 2020 from 5 GW to 8.4 GW facilitates additional imports and brings down the annual cost of electricity for GB consumers by €639m. Analysis for 2025 and 2030 shows that additional interconnectors, the removal of the additional GB carbon tax and changes to the generation background lead to GB experiencing increased interconnector exports and reduced interconnector utilisation. This lessens or reverses the impact of new GB interconnection on GB consumer prices. It also leads to a significant reduction in revenue potential for future interconnectors. Carbon emission analysis indicates that inconsistencies in carbon pricing across different countries, like the extra GB price support, can lead to perverse outcomes with reduced GB emissions but increased total European emissions

Electrical interconnectors : market opportunities, regulatory issues, technology considerations and implications for the GB energy sector

The linking of different jurisdictions or markets via electrical interconnection is a long established means of offering enhanced security of supply to the wider electrical system. In recent years, new incentives around exploiting market price differentials and facilitating the growth of renewable energy have represented the primary motivation for new interconnector projects. This paper provides a comprehensive overview of the technical options for delivering interconnectors, examines historical trends and discusses the ownership models, regulatory frameworks and market structures within which the investment case for new interconnectors must be made. Drawing on both technical and market considerations, the paper sets out the potential impact that interconnectors can have on the energy market and interested actors within connected markets before discussing in more detail the policy implications of the proposed roll out of new interconnector projects to the GB energy sector and suggests a number of factors beyond the current focus on consumer welfare could be given more prominence in the policy making around interconnector investment. The ways in which the UK's withdrawal from the European Union might impact on future and existing interconnectors in Britain is also discussed

A reliability evaluation of offshore HVDC transmission network options

There are ambitious targets in place for the development of large amounts of offshore renewable energy in the coming years. The offshore wind sector is expected to provide the vast majority of the projected growth which means large scale and far from shore projects are likely to become common. The transmission distances involved suggest HVDC technology is likely to be deployed and analysis to date has suggested there will be value in delivering co-ordinated offshore grids as opposed to simpler radial connection to shore. However, there are numerous technology and design options available for the delivery of offshore HVDC networks and, given the offshore climate can makes access for component maintenance or repair challenging, the reliability performance of different options is an important factor which has not been explored in much of the existing literature. This thesis details a novel methodology for investigating the reliability of different offshore grid design options for the connection of offshore wind power to shore or the interconnection of regions. A sequential Monte Carlo simulation methodology is used that allows investigation of realistic offshore phenomena such as the weather dependency of component repair times. A number of case studies are examined and a full cost benefit analysis is performed which compares the capital and operational costs, electrical losses and reliability performance of each grid option. There is shown to be clear value in options that include a degree of inherent redundancy and it is also shown that alternative protection strategies which avoid the use of expensive DC circuit breakers are potentially viable at lower cost and little expense to performance. An investigation of the key drivers behind overall offshore grid reliability is also made and it is found that low probability, high impact faults such as transmission branch failures have the greatest influence.There are ambitious targets in place for the development of large amounts of offshore renewable energy in the coming years. The offshore wind sector is expected to provide the vast majority of the projected growth which means large scale and far from shore projects are likely to become common. The transmission distances involved suggest HVDC technology is likely to be deployed and analysis to date has suggested there will be value in delivering co-ordinated offshore grids as opposed to simpler radial connection to shore. However, there are numerous technology and design options available for the delivery of offshore HVDC networks and, given the offshore climate can makes access for component maintenance or repair challenging, the reliability performance of different options is an important factor which has not been explored in much of the existing literature. This thesis details a novel methodology for investigating the reliability of different offshore grid design options for the connection of offshore wind power to shore or the interconnection of regions. A sequential Monte Carlo simulation methodology is used that allows investigation of realistic offshore phenomena such as the weather dependency of component repair times. A number of case studies are examined and a full cost benefit analysis is performed which compares the capital and operational costs, electrical losses and reliability performance of each grid option. There is shown to be clear value in options that include a degree of inherent redundancy and it is also shown that alternative protection strategies which avoid the use of expensive DC circuit breakers are potentially viable at lower cost and little expense to performance. An investigation of the key drivers behind overall offshore grid reliability is also made and it is found that low probability, high impact faults such as transmission branch failures have the greatest influence