Interconnected Transmission Research Articles

Life-cycle environmental performance assessment of electricity generation and transmission systems in Greece

The purpose of this paper is to present an integrated life cycle assessment of the electricity grid of Greece, considering the different power generation technologies currently operating in the country and the interconnected electricity transmission system. The energy and environmental assessment of both the generation and transmission systems is carried out employing SimaPro 7.1 Life Cycle Assessment software. The present work shows that the main, environmentally adverse, impacts (>60%) are associated with the electricity generation sector; in particular, with the system of mainland Greece, which is dominated by centralized fossil-fuelled power plants. Transmission of electricity was found to have 70%–90% lower life cycle impacts compared to generation. Transmission power losses are the most important contributor to GHG emissions, whereas transmission lines infrastructure and transformers are associated with much lower life cycle impacts. Findings concerning the primary energy demand exhibit analogous behaviour. Future electricity supply mixes with high shares of renewables could lead to substantially lower GHG emissions, whilst primary energy demand is expected to increase, due to the electricity intensive construction stage of renewables. Results concerning the contribution of electricity generation and transmission to environmental impacts related to human toxicity, ecosystem quality, resources depletion, etc., are also reported and discussed.

False Data Injection Attacks With Limited Susceptance Information and New Countermeasures in Smart Grid

In this paper, we consider false data injection (FDI) attacks with limited information of transmission-line susceptances and new countermeasures in smart grids. First, we prove that the adversary could launch FDI attacks to modify the state variable on a bus or superbus only if he/she knows the susceptance of every transmission line that is incident to that bus or superbus. Based on this observation, we provide a new countermeasure against FDI attacks, i.e., to make the susceptances of n-1 interconnected transmission lines that cover all buses unknown to the adversary (e.g., by proactively perturbing transmission-line susceptances through distributed flexible AC transmission system (D-FACTS) devices), where n is the total number of buses. This new countermeasure can work alone or in conjunction with traditional ones to reduce the number of meter measurements/state variables that are to be secured against FDI attacks. The implementation of FDI attacks with limited susceptance information and the effectiveness of new countermeasures are demonstrated by using an illustrative 4-bus power system and the IEEE 9-bus, 14-bus, 30-bus, 118-bus, and 300-bus test power systems.

Flexible electricity generation, grid exchange and storage for the transition to a 100% renewable energy system in Europe

Two transition pathways towards a 100% renewable energy (RE) power sector by 2050 are simulated for Europe using the LUT Energy System Transition model. The first is a Regions scenario, whereby regions are modelled independently, and the second is an Area scenario, which has transmission interconnections between regions. Modelling is performed in hourly resolution for 5-year time intervals, from 2015 to 2050, and considers current capacities and ages of power plants, as well as projected increases in future electricity demands. Results of the optimisation suggest that the levelised cost of electricity could fall from the current 69 €/MWh to 56 €/MWh in the Regions scenario and 51 €/MWh in the Area scenario through the adoption of low cost, flexible RE generation and energy storage. Further savings can result from increasing transmission interconnections by a factor of approximately four. This suggests that there is merit in further development of a European Energy Union, one that provides clear governance at a European level, but allows for development that is appropriate for regional contexts. This is the essence of a SuperSmart approach. A 100% RE energy system for Europe is economically competitive, technologically feasible, and consistent with targets of the Paris Agreement.

Temperature Field Reconstruction of Concrete Dams based on Distributed Optical Fiber Monitoring Data

Mastering the real temperature distribution of the concrete dam is the basis for solving the problem of temperature control and crack prevention. In this paper, Distributed Temperature Sensing (DTS) technology was applied to temperature monitoring of a high-arch dam under construction in southwest China. In order to obtain a more comprehensive temperature distribution of the dam, optical fiber layout principles for arch dams were studied, and horizontal and vertical optical fiber layout schemes were first proposed according to these principles. The real temperature variation processes of the dam were obtained in real time with a line temperature measurement pattern instead of a point temperature measurement pattern. Additionally, a framework of distributed optical fiber data acquisition and remote transmission was proposed. Interconnection of multiple DTS hosts and remote transmission of temperature data were realized. Then, two-dimensional temperature fields of a typical dam block in different ages and longitudinal profiles of dam blocks with embedded fibers were reconstructed based on large amounts of temperature monitoring data and the Kriging difference algorithm. Temperature field reconstruction results showed that the temperature distribution law of the concrete arch dam was in accordance with the actual situation.

Large scale photovoltaics and the future energy system requirement

Supported by conducive policy and technology cost decline, PV capacity addition is increasing rapidly. The capacity addition is forecasted to continue at a faster rate over the coming decades. With such an increase, it is important to ask about system requirement to effectively integrate large system into a power grid. This paper presents the analysis of literature data in order to clarify system requirement for large PV integration. The review shows that the most important challenges of large-scale PV penetration are matching, variability, uncertainty and system adequacy. To overcome these challenges, several enabling techniques, such as energy storage, curtailment, transmission interconnection, demand response, resource complementarities, increased grid flexibility, improved forecasting, geographic distribution of generation resources, were among the most discussed by various researcher. A closer look at some systematic studies shows that developing theoretical framework for the future system is the best way to guide the smooth development of an effective and secure system. This argument is based on the observation that (i) the role and importance of one technology, for instance specific storage technology, may change as VRE penetration increases; (ii) the increase in use of one application decreases the importance of the other; (iii) the use of some of the discussed solutions may depend on level of penetration as they also depend on season. Thus, it is important to design the system based on a criteria formulated with the understanding of system level science/theoretical framework.

Optimal Placement of an Unified Power Flow Controller in a Transmission Network by Unified Non Dominated Sorting Genetic Algorithm-III and Differential Evolution Algorithm

The interconnected transmission network of the Benin Electric Community (CEB) presents excessive losses that will increase further by 2025 and severely degrade the power quality supplying. This paper presents the quarto-criterion optimization of the positioning of a UPFC in the CEB's HTB network by U-NSGA III and DE. The positioning of an UPFC on line 3 and node 6 of this network has qualitatively improved the technical performance of this transmission network with an optimal installation cost of US $ 13126657.03. The hypervolumes of the two calculated methods showed that the U-NSGA-III is more accurate in terms of trend toward global solutions than DE. These convincing results confirm the performance of the U-NSGA-III method compared to the DE which also resulted in results close to those obtained by the U-NSGA-III with more or less narrow difference.

An economic benefit evaluation model and its application for optimizing transmission capacity of multinational interconnections

Multinational power grid interconnections play a critical part in supporting the vision of global energy internet. During the early stages of the Global Energy Internet, the value proposition of multinational interconnections should be carefully investigated in order to stimulate the activities for associated countries in such potential interconnections. This paper proposes a new e conomic benefit evaluation model which is quantified by using a chronological production cost simulation approach. The economic benefit model comprehensively considered investment costs and the benefits of the decrease of load payments and the increase of net generation revenue due to a transmission project interconnected with different countries. This economic benefit model can assist to quantitatively determine the optimal transmission capacity for multinational interconnections to achieve maximum economic benefits as a whole. In the case study, the economic benefit of an interconnected system of western China and the Gulf States is assessed by using the method proposed in this paper. And the optimal interconnection capacity with maximum benefit is achieved. The case study shows that the proposed method can be used for economic benefit assessment and is of great significance to the multinational and inter-continental transmission interconnections.

Advancing Principles and Strategies of Power Grid Interconnection in the Belt and Road

Promoting the “Belt and Road” grid interconnection and cross-border transmission channel construction is of great significance in optimizing the global energy governance structure, realizing complementary advantages and mutually beneficial cooperation with the countries along the route, assisting regional economic integration, and building a human destiny community. Based on an analysis of the status, future development trend and challenges of power grid interconnection in the B&R area, the basic principles and overall strategy for promoting transnational power grid interconnection in the B&R is proposed.

Proposed Scheme of Pliable Gas Insulated Transmission Line and Its Comparative Appraisal Regarding Electrostatic and Dielectric Aspects

Gas insulated transmission lines (GILs) are being used in electrical systems regarding power transmission and substation interconnection. However, operational complexities of conventional schemes, such as structural rigidity, corrosion protection, gas leakage in case of seismic vibrations, larger bending radius and jointing complexities which restrain their application perspectives, could be curtailed by developing a flexible GIL. In this research paper, a new pliable scheme of gas insulated transmission line is proposed. Further, COMSOL Multiphysics® (version 5.1, COMSOL Inc., Stockholm, Sweden) based electrostatic assay and practically performed high voltage tests-based dielectric analysis is performed for the proposed scheme. Electrostatic appraisal is comprised of field utilization based electrostatic stress analysis. In addition, dimensional optimization of pliable GIL regarding enclosure and pitch sizes in relation to electrostatic stresses and field utilization is also performed. Regarding dielectric perusal, experimental setup has been developed for standard lightning impulse and disruptive discharge tests in order to investigate the synergistic dielectric characteristics of proposed flexible post insulators for pliable GIL. Experimental and simulation appraisal unveil that the proposed scheme exhibits almost analogous electrostatic and dielectric behavior in comparison to the conventional GIL scheme and could simplify the operational intricacies associated with conventional scheme. The proposed modifications could eliminate the requirement of trench development, corrosion protection and acceleration dampers, along with a significant reduction in required land area at bends, due to a smaller bending radius which will ultimately result in substantial cost reduction.

A Mechanism for Allocating Benefits and Costs from Transmission Interconnections under Cooperation: A Case Study of the North Sea Offshore Grid

We propose a generic mechanism for allocating the benefits and costs that result from the development of international transmission interconnections under a cooperative agreement. The mechanism is based on a planning model that considers generation investments as a response to transmission developments, and the Shapley Value from cooperative game theory. This method provides a unique allocation of benefits and costs considering each country’s average incremental contribution to the cooperative agreement. The allocation satisfies an axiomatic definition of fairness. We demonstrate our results for three planned transmission interconnections in the North Sea and show that the proposed mechanism can be used as a basis for defining a set of Power Purchase Agreements among countries.

Resilient Off-Grid Microgrids: Capacity Planning and N-1 Security

Over the past century the electric power industry has evolved to support the delivery of power over long distances with highly interconnected transmission systems. Despite this evolution, some remote communities are not connected to these systems. These communities rely on small, disconnected distribution systems, i.e., microgrids to deliver power. However, as microgrids often are not held to the same reliability standards as transmission grids, remote communities can be at risk for extended blackouts. To address this issue, we develop an optimization model and an algorithm for capacity planning and operations of microgrids that include ${N}$ -1 security and other practical modeling features like ac power flow physics, component efficiencies, and thermal limits. We demonstrate the computational effectiveness of our approach on two test systems; a modified version of the IEEE 13 node test feeder and a model of a distribution system in a remote community in Alaska.

Performance Improvement of Various Types of Induction-based Wind Farms Using Center-node Unified Power Flow Controller

In this paper, we propose the use of center-node unified power flow controller (C-UPFC) for improving the performance of different types of wind farms and mitigating their negative impacts on the grid. C-UPFC is considered one of the modernist members on Flexible AC Transmission System (FACTS). C-stocktickerUPFC has the ability to control several system parameters; the active and reactive power at both ends of the interconnected transmission line and the voltage at the midpoint. Three different induction-based wind farms are considered; 1) Squirrel Cage Induction Generator (SCIG), 2) Doubly Fed Induction Generator (DFIG), and 3) a combination of SCIG and DFIG turbines, i.e., Combined Wind Farm (CWF). C-stocktickerUPFC is comprehensively modelled for the first time in MATLAB Simulink, then the performance of the three wind farms is assessed with and without this device during three phase faults. Probabilistic voltage stability index (Probabilistic VSI) is used to measure the stability of the studied systems. In addition, the performance of three wind farms integrated with C-UPFC is compared with their performance when they integrated with Static synchronous compensators (STATCOM). The results show that C-UPFC has the ability to enhance the performance of wind farms during the three phase fault. C-UPFC is capable to remain the connection between SCIG wind farm and the interconnected grid during the fault. The voltage of CWF is greatly enhanced in the case of using C-UPFC. C-UPFC also improves the output powers of DFIG and CWF, especially after fault clearance.

Wideband arbitrary phase‐difference coupled‐line coupler with tight coupling coefficient and small phase variation

In this study, a planar arbitrary phase-difference coupled-line coupler having wide bandwidth, tight coupling coefficient, and small phase variation are proposed. The proposed coupler consists of two quarter-wavelength coupled-line sections connected with two different transmission lines. Moreover, the interconnection transmission line can be designed as a small phase variation phase shifter with the introduction of a shorted stub. The detailed theoretical analysis is provided to illustrate the design concept. The circuit parameters of this novel arbitrary phase-difference coupler can be easily determined by the derived closed-form equations. For verification, two 3 dB couplers with 45°/135° and 60°/120° phase differences are fabricated and measured. The 45°/135° coupler achieves 34.2% fractional bandwidth for 45° phase difference with 2° phase variation and 36.3% fractional bandwidth for 135° phase difference with 3.4° phase variation. Moreover, the 60°/120° coupler achieves 30% fractional bandwidth for 60° phase difference with 0.9° phase variation and 32.9% fractional bandwidth for 120° phase difference with 1.5° phase variation.

Impact of dynamic line rating on operational planning calculations of interconnected transmission systems

Impact of dynamic line rating on operational planning calculations of interconnected transmission systems

A Novel Dual-Sided Fly-By Topology for 1–8 DDR With Optimized Signal Integrity by EBG Design

A novel dual-sided fly-by topology is proposed for one controller to multiple memory systems by choosing interconnected transmission line sections of alternate impedance and length. After suitable big data analysis of automatic simulation, peak distortion analysis for eye height, followed by artificial neural network optimization, the best design guideline can be deduced, which is found to be consistent to the electromagnetic bandgap (EBG) theory. The topology may greatly enhance the eye height by 20%–100% while the total length is reduced by half, compared with the conventional fly-by topology. The general design method, relevant simulation, and analysis from EBG are also provided. Measurement has been performed to validate the new design, demonstrating 53% improvement in eye height over the conventional one.

Regional electricity trade for hydropower development in South Asia

ABSTRACT This study examines the importance of enhancing cross-border transmission interconnections and regional electricity trade to promote hydropower in the South Asia region and it quantifies the potential of hydropower development and trade under alternative scenarios. The paper shows that regional electricity trade is critical for the exploitation of the untapped hydropower resources in South Asia. It finds that hydropower capacity would increase by 2.7 times over the next two decades if a regional electricity market is developed. If a moderate carbon tax is added on top of it, hydropower capacity would be more than three times higher than the current level.

Estimating the value of offshore wind along the United States’ Eastern Coast

Offshore wind power deployment has been concentrated in Europe, and remains limited in other areas of the world. Among the many challenges to deployment is the need to understand the value that offshore wind provides within electricity markets. This article develops a rigorous method to assess the economic value of offshore wind along the eastern coastline of the United States, seeking improved understanding of how the value of offshore wind varies both geographically and over time, and what has driven that variation. The article uses historical (2007–2016) weather data at thousands of potential offshore wind sites, combined with historical wholesale electricity market outcomes and renewable energy certificate (REC) prices at hundreds of possible transmission interconnection points. We find that the average historical market value of offshore wind from 2007 to 2016—considering energy, capacity, and RECs—varies significantly by project location, from $40/MWh to more than $110/MWh, and is highest for sites off of New York, Connecticut, Rhode Island, and Massachusetts. As energy and REC prices have fallen in recent years, so too has the market value of offshore wind. The historical value of offshore wind is found to exceed that of onshore wind, due to offshore wind sites being located more favorably in terms of constrained pricing points, and also due to a more-favorable temporal profile of electricity production. Cost reductions that approximate those witnessed recently in Europe may be needed for offshore wind to offer a credible economic value proposition on a widespread basis in the United States.

A generative graph model for electrical infrastructure networks

We propose a generative graph model for electrical infrastructure networks that accounts for heterogeneity in both node and edge type. To inform the model design, we analyze the properties of power grid graphs derived from the U.S. Eastern Interconnection, Texas Interconnection, and Poland transmission system power grids. Across these datasets, we find subgraphs induced by nodes of the same voltage level exhibit shared structural properties atypical to small-world networks, including low local clustering, large diameter, and large average distance. On the other hand, we find subgraphs induced by transformer edges linking nodes of different voltage types contain a more limited structure, consisting mainly of small, disjoint star graphs. The goal of our proposed model is to match both these inter and intra-network properties by proceeding in two phases: the first phase adapts the Chung-Lu random graph model, taking desired vertex degrees and desired diameter as inputs, while the second phase of the model is based on a simpler random star graph generation process. We test the model's performance by comparing its output across many runs to the aforementioned real data. In nearly all categories tested, we find our model is more accurate in reproducing the unusual mixture of properties apparent in the data than the Chung-Lu model. We also include graph visualization comparisons, a brief analysis of edge-deletion resiliency, and guidelines for artificially generating the model inputs in the absence of real data.

Robust Power Flow and Three-Phase Power Flow Analyses

Robust simulation is essential for reliable operation and planning of transmission and distribution power grids. At present, disparate methods exist for steady-state analysis of the transmission (power flow) and distribution power grid (three-phase power flow). Due to the non-linear nature of the problem, it is difficult for alternating current (AC) power flow and three-phase power flow analyses to ensure convergence to the correct physical solution, particularly from arbitrary initial conditions, or when evaluating a change (e.g. contingency) in the grid. In this paper, we describe our equivalent circuit formulation approach with current and voltage variables that models both the positive sequence network of the transmission grid and three-phase network of the distribution grid without loss of generality. The proposed circuit models and formalism enable the extension and application of circuit simulation techniques to solve for the steady-state solution with excellent robustness of convergence. Examples for positive sequence transmission and three-phase distribution systems, including actual 75k+ nodes Eastern Interconnection transmission test cases and 8k+ nodes taxonomy distribution test cases, are solved from arbitrary initial guesses to demonstrate the efficacy of our approach.

Origin and mitigation of increased electric fields at high voltage transmission line conductors

In this paper analysis of the origin and mitigation measures of increased electric field at high voltage transmission lines in the electric power system of Bosnia and Herzegovina is given. In the analyzed period (2010–2017) in the electric power system of Bosnia and Herzegovina increased values of power frequency voltages was registered. The performed analysis shows that the increased voltages in the 400 kV nodes of the electric power system of Bosnia and Herzegovina are occurring during the night, mainly in the minimum consumption regimes. Increased voltages can occur throughout the year, but are most frequent during the spring and summer months. In the coming years, four 400 kV interconnection transmission lines to Serbia and Croatia will be built. Increasing of the voltage value causes the formation of the corona as well as energy losses. Taking into account the values of the energy losses due to the corona, it is important to determine the values of the electric field on the surface of the conductors and their immediate vicinity as well as the value of the corona onset electric field in order to know their values in the electric power system and to explore ways to mitigation them from the aspect of maintenance and management costs.