National Transmission Research Articles

Staying positive: producing net power.

The Spherical Tokamak for Energy Production (STEP) prototype powerplant (SPP) will be a first-of-a-kind powerplant-its prime objective is to export electrical power, to the national power transmission system ('grid'), above 100 MWe. As part of a wider issue, addressing the STEP concept design, this article seeks to explore how electrical power will be generated from a spherical tokamak heat source. Accordingly, the following key functions of the SPP power infrastructure are reviewed.Cooling the tokamak: cooling the tokamak while extracting useful thermal energy.Generating power: conversion of thermal energy to electrical energy (power generation).Managing energy: management of the site-wide distribution, storage and energy export.In each of these areas, the design scope, challenges and solution spaces have been discussed. This has shaped the design of the SPP power infrastructure, which in turn has ensured a powerplant design focused on operability and performance. Furthermore, it has been demonstrated that the SPP will achieve its prime objective in generating net power, which is enabled by a unique power infrastructure. Confidence in the ability to generate net power will be refined as the design matures. Finally, this article recommends key opportunities that STEP could use to improve power generation and reduce the parasitic load of the SPP.This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.

Integrating geographic intelligence for sustainable powerline planning

This research explores the potential of geographic intelligence in modelling optimal corridors for assessing alternative locations for power transmission lines at different stages of the study. The difficulties verified in the environmental licensing of new projects, the expansion of the national transmission system, and the lack of work to research techniques for formulating locational alternatives are motivating questions for this research. The investigation employs a multicriteria decision-making approach integrated with a geographic information framework to compute and map the feasibility corridors based on environmental constraints and stakeholder inputs. Findings reveal that the current decision-making process for implementing new power transmission lines involves disparate public and private entities operating non-integratively in a multi-level analysis and decision-making process. Through a case study utilising multicriteria analysis and expert consultations, the research demonstrates the applicability of spatial modelling in the locational planning of transmission projects. It highlights the model's capacity to address the complexity inherent in such studies, aggregate analyses and decisions from various stakeholders, and enhance transparency in the decision-making process from energy planning to operational phases.

Decentralised Cross-Border Interconnection

Reaping the full benefits from cross-border interconnection typically requires reinforcement of national networks. When the relevant parts of the networks are complements, a lack of coordination between national transmission system operators results in investment below optimal levels in both interconnectors and national infrastructure. A subsidy to financially sustain interconnector building is not sufficient to restore optimality; indeed, even when possible, such subsidisation may have to be restrained so as not to encourage cross-border capacities that will not be fully utilised due to lack of investment in national systems.

Управління проєктами розвитку газотранспортної системи України в контексті підвищення загроз енергетичній безпеці в умовах війни

The article examines the current problems of the development and modernization of the Ukrainian national gas transmission system in the context of the implementation of the main strategic tasks (according to the New Energy Strategy of Ukraine) and a number of provisions regulating the legal basis of the functioning of the natural gas market of Ukraine (in particular, the Law of Ukraine "On the Natural Gas Market"). However, Russia's invasion of Ukraine not only made it impossible to fulfill these tasks, but also led to the disruption of the global energy market and the world energy security system. Today, there is an urgent need to transform Europe's energy system, coordinate planning and financing of cross-border and national infrastructure, as well as the development and implementation of a large number of various energy projects.The need for a new approach to EU-wide infrastructure planning based on regional cooperation with Member States and relevant stakeholders to identify projects of common interest (PCIs) that contribute to the development of energy infrastructure priority corridors and thematic areas is proven. It is justified that the possibilities of transportation and storage of renewable gases (hydrogen, biomethane and synthetic methane) become one of the priority tasks for Ukraine, which offers itself to Europe as a promising and reliable partner.

European and Indian Grid Codes for Utility Scale Hybrid Power Plants

The aim of this paper is to review and compare present European and Indian grid code requirements imposed to hybrid power plants (HPPs) combining wind, solar and storage technologies. Since there are no grid codes specifically for HPPs, the paper will review grid codes for the power plant based on individual renewable technology in the HPP. European grid codes specifies ranges for parameters inside which each national transmission system operators (TSO) has to specify the set of national parameters (Danish specifications in this paper). The comparisons are performed with respect to fault-ride-through capability, frequency and voltage operation ranges, active power control/frequency support as well as reactive power control/voltage support.

РОЗРАХУНОК ДОЦІЛЬНОГО ОБСЯГУ АВТОМАТИЧНОГО ЧАСТОТНОГО РОЗВАНТАЖЕННЯ І ЙОГО РОЗМІЩЕННЯ В ЕНЕРГОСИСТЕМІ З РОЗПОДІЛЕНИМИ ДЖЕРЕЛАМИ ЕЛЕКТРИЧНОЇ ЕНЕРГІЇ

Система автоматичного частотного розвантаження (АЧР) є одним із основних засобів, який широко застосовується в енергосистемах для стримування швидкого падіння частоти. Система АЧР здатна за мілісекунди відключити частину споживачів, а за секунди – зупинити падіння частоти в районах енергосистеми, які утворилися в результаті каскадної аварії з відключення ліній і генераторів. Для підтримки тимчасового балансу активної потужності в аварійних ситуаціях в енергосистемі повинна бути передбачена кількість навантаження на відключення.
 Тому національні оператори систем передачі або мережа операторів систем передачі електроенергії встановлюють так званий загальний обсяг розвантаження. Найчастіше в стандартах та нормативних документах енергосистем цей показник розраховують для загального пікового попиту і рекомендують розмістити в енергосистемі рівномірним географічним способом. Такий спосіб розміщення загального обсягу розвантаження не враховує структуру електромережі, добової та сезонної зміни потужностей генерації і споживання, незважаючи на те, що стандарти, нормативні документи вимагають це враховувати. В роботі запропоновано математичну модель і спосіб визначення загального обсягу розвантаження системи АЧР і його розміщення в мережі енергосистеми з урахуванням розподілених (у вузлах споживачів) відновлюваних джерел енергії, ймовірних варіантів аварійного поділу енергосистеми, вимог міжнародних стандартів та нормативних документів, що регулюють функціонування систем протиаварійного захисту в галузі електроенергетики. Модель являє собою задачу цілочисельного (бінарного) лінійного програмування, що здійснює вибір оптимального за критерієм категорійності набору пристроїв АЧР, які розміщені у наперед заданих вузлах енергосистеми і спрацювання яких забезпечує баланс потужності в аварійних районах її поділу. Електричні параметри усталених режимів, а також ефективність оптимального обсягу і розподілу розвантаження в мережі визначаються і перевіряються (верифікуються) у серії апріорних та апостеріорних розрахунків на точних математичних моделях, визнаних у світовій практиці програмних продуктів електроенергетики. Отриманий таким чином розподіл обсягів розвантаження підвищує імовірність балансування якнайбільшої кількості аварійних районів енергосистеми за умови задоволення вимог щодо частотно-часової зони відповідних перехідних процесів. Бібл. 9, табл. 3, рис. 2.

Challenge of Renewable Energy Transition towards Krabi’s Sustainable Energy City

This paper is a review article collecting relevant data and information for developing a transition model towards a sustainable energy city: a case study of Krabi Province, Thailand. An expanding tourism sector in Krabi is increasing energy demand, which continues to grow year after year. Meanwhile, the energy supply of the province relies on the centralization of the southern and central regional energy system to the national grid transmission system. According to the 2018 National Power Development Plan, Krabi is projected to shift to regional grid decentralization; coupled with increasing its power generation from renewable energy with affordability and community participation. Therefore, Krabi Vision 2020, which is a provincial master plan, would lead the direction of Krabi’s plan towards energy transition. Increasing renewable energy investment and disruptive technology to secure the potential of solar, biomass, biogas, wind and mini-hydro is paving the way to shift Krabi to a sustainable energy future. The implementation of a sustainable energy transition across the province, would bring benefits for the local economy, environmental conservation, and energy security. To achieve this energy transition, Krabi requires coordination of smart policy, local and government participation, and sound planning. This review study suggests that the transition towards a sustainable energy future depends on identifying the political barriers, and the adoption of effective management practices.

Analysis of the Integration of Wind Energy Generation in the National Transmission System (NTS)

Background/Objectives: A case study is presented where a 1.432 MW wind power connection with DFIG (doubly-fed induction generator) technology is analyzed in the stability of the National Transmission System (NTS). Hence, the STN’s database from 2017 is used in DIgSILENT with different demand scenarios and their respective generation dispatch units. Methods/Statistical Analysis: A scan was executed on the flaws in circuits close to the connection of wind energy parks in La Guajira by calculating the percentage of events that generate the disconnection of wind turbines due to voltage sags and swells. The stability in frequency in response to these generation losses is also analyzed. Findings: Regarding the contingencies that were simulated, the outcome was seen in overshoot events of wind turbines due to transitory peaks in voltage during flaws that could not be solved with external reactive compensation. The stability in frequency related to these overshoots is greatly affected on disconnections higher than 400 MW. After verifying the reactive power injection from the converter of the DFIG model in DIgSILENT based on the compliance with electrical parameters supplied by manufacturers, 58% did not meet these technical specifications so a wind turbine model is necessary to grasp the internal operation of the converter. Conclusion: This allows the identification of possible solutions to stability issues that contribute to the operational and regulatory changes to define technical technology-related requirements and the connection of wind turbines in Colombia. Keywords: DFIG Wind Turbine, DIgSILENT, Stability, Voltage Supportability, Wind Energy

Assessing fugitive emissions of CH4 from high-pressure gas pipelines in the UK

Natural gas pipelines are an important source of fugitive methane emissions in lifecycle greenhouse gas assessments but limited monitoring has taken place of UK pipelines to quantify fugitive emissions. This study investigated methane emissions from the UK high-pressure pipeline system (National Transmission System - NTS) for natural gas pipelines. Mobile surveys of CH4 emissions were conducted across four areas in the UK, with routes bisecting high-pressure pipelines (with a maximum operating pressure of 85bar) and separate control routes away from the pipelines. A manual survey of soil gas measurements was also conducted along one of the high-pressure pipelines using a tunable diode laser. For the pipeline routes, there were 26 peaks above 2.1ppmv CH4 at 0.23peaks/km, compared with 12 peaks at 0.11peaks/km on control routes. Three distinct thermogenic emissions were identified on the basis of the isotopic signal from these elevated concentrations with a peak rate of 0.03peaks/km. A further three thermogenic emissions on pipeline routes were associated with pipeline infrastructure. Methane fluxes from control routes were statistically significantly lower than the fluxes measured on pipeline routes, with an overall pipeline flux of 627 (241–1123 interquartile range) tonnes CH4/km/yr. Soil gas CH4 measurements indicated a total flux of 62.6ktCH4/yr, which equates to 2.9% of total annual CH4 emissions in the UK. We recommend further monitoring of the UK natural gas pipeline network, with assessments of transmission and distribution stations, and distribution pipelines necessary.

Evaluación de la Distorsión Armónica debida a la Operación del Compensador Estático de Potencia Reactiva en la Subestación Chorrillos

La subestación Chorrillos 500/230 kV, la cual forma parte del plan de expansión del nuevo sistema de 500 kV del Ecuador, incorpora en una de sus bahías un Compensador Estático de Potencia Reactiva (SVC por sus siglas en inglés). Este equipo permite un control de voltaje en la barra de 230 kV de esta subestación a través del uso de tiristores para el control de corriente. Sin embargo, la maniobra de estos dispositivos semiconductores produce distorsiones en la forma de onda de corriente y voltaje.
 Por lo antes mencionado, el presente trabajo muestra la modelación del SVC en el programa computacional PowerFactory, y determina, para diferentes escenarios de operación, el efecto del contenido armónico sobre el Sistema Nacional de Transmisión (SNT).
 El resultado del efecto armónico provocado por este equipo sumado al contenido armónico preexistente en el SNT permite determinar si los armónicos de voltaje y corriente se encuentran dentro de los límites establecidos en la regulación CONELEC 003/08.
 Adicionalmente se analiza el K-Factor y Factor K en los transformadores del SNT, considerando el efecto armónico producido por la operación del SVC

Determination of the Safety Distances Between Natural Gas Transmission Pipelines and Facilities in their Proximity

The paper presents the particularities of accomplishing risk analyses with the purpose of establishing the safety distances � SD, between the pipes belonging to the natural gas national transmission system � NTS and facilities (people, animals, buildings, crops, orchards, forests etc.) placed in the their vicinity. In order to check if the distances between the National Gas Transportation Pipeline- NGTP and neighboring facilities are SD, the authors developed a procedure and a software for the risk assessment, which make use of a set of formulas validated by experimental results presented in the paper and information from the data base (built by the authors and presented briefly in our work) regarding the supervision of the technical state and recording of the accidents that took place in the last 19 years on the NGTP from NTS. Also, in the paper, one describes the way the technical solutions verified using the procedure and the software built by the authors can be selected and ranked (in view of implementation) by applying the ALARP principle and the cost � benefit analysis.

Metodología para la Determinación de Ángulos de Sincronismo y Tiempos de Recierre en el Sistema Nacional Interconectado

La sincronización de líneas de transmisión, ya sea por su normalización posterior a trabajos de mantenimiento, o sincronización de islas eléctricas durante maniobras de restablecimiento de un sistema de potencia es una maniobra crítica tanto para equipos de transmisión como para unidades de generación. Adicionalmente, la operación exitosa de recierres automáticos es importante por razones de seguridad o confiabilidad. Por lo antes mencionado, el presente trabajo pretende establecer una metodología adecuada para la parametrización de los relés de sincronismo en líneas del Sistema Nacional de Transmisión (SNT) del Ecuador, especialmente en relación a la diferencia angular máxima permitida entre los polos del interruptor asociado, considerando los posibles efectos sobre interruptores de potencia y unidades de generación. Con la finalidad de verificar que las variables eléctricas relevantes, identificadas en la metodología planteada, no superen los límites máximos permisibles se realizan numerosas simulaciones dinámicas en líneas de transmisión del anillo de 230 kV del SNT.
 Los resultados obtenidos permitirán determinar los ajustes apropiados de diferencia angular para la sincronización en el anillo de 230 kV del sistema eléctrico ecuatoriano.

EU energy policies achievement by industries in decentralized areas

Energy Roadmap outlined by the European Commission sets out several routes for a more sustainable, competitive and secure energy system in 2050. All the outlined scenarios consider energy efficiency, renewable energy, nuclear energy and carbon capture and storage. In this paper, more attention has been devoted to the energy efficiency issue, by the identification of new micro and small networks opportunity fed by hybrid plants in the North-East of Italy. National energy balance and national transmission system operator data allowed to collect industrial energy consumptions data on the investigated area. Applying industrial statistics to the local energy needs allows to collect a dataset including consumption information by factory and by company structure (size and employees) for each industrial sector highlighting the factory density in the area. Preliminary outcomes from the model address to the exploitation of local by-product for energy purposes.

Coordinating Cross-Country Congestion Management: Evidence from Central Europe

We employ a detailed two-stage model to simulate the operation of the Central Eastern European electricity market and network. Implementing different cases of coordination in congestion management between national transmission system operators, numerical results show the beneficial impact of closer cooperation. Specific steps comprise the sharing of network and dispatch information, cross-border counter-trading, and multilateral redispatch in a flow-based congestion management framework. Efficiency gains are accompanied by distributional effects. Closer economic cooperation becomes especially relevant against the background of changing spatial generation patterns, deeper international integration of national systems, and spillovers of national developments to adjacent systems.

Coordinating Cross-Country Congestion Management

We employ a detailed two-stage model to simulate the operation of the Central Eastern European electricity market and network. Implementing different cases of coordination in congestion management between national transmission system operators, numerical results show the beneficial impact of closer cooperation. Specific steps comprise the sharing of network and dispatch information, cross-border counter-trading, and multilateral redispatch in a flow-based congestion management framework. Efficiency gains are accompanied by distributional effects. Closer economic cooperation becomes especially relevant against the background of changing spatial generation patterns, deeper international integration of national systems, and spillovers of national developments to adjacent systems.

Sistema de Protección Sistémica Considerando la Expansión de Generación y Transmisión en el Sistema Ecuatoriano

En el sistema eléctrico ecuatoriano en marzo del 2015 se implementó un Sistema de Protección Sistémica (SPS), cuya función es la de detectar la ocurrencia de contingencias críticas, previamente identificadas, y ejecutar las acciones remediales definidas para cada una de esas contingencias. Considerando el ingreso a operación de las nuevas obras de generación y transmisión en el Sistema Nacional Interconectado (S.N.I.), en el mediano plazo, las condiciones de operación se modifican y por lo tanto se requiere la actualización del SPS. En este sentido, en este documento se presentan los criterios y resultados del análisis de contingencias simples y dobles en el Sistema Nacional de Transmisión (SNT), para determinar las contingencias críticas bajo nuevos escenarios de operación y se plantean las acciones remediales que le permitan al S.N.I. mantener una operación segura.

Decision support for restoration of interconnected power systems using tie lines

Existing system restoration strategies are primarily based on operators’ experience with no specific decision support tools. Restoration of interconnected grids in Europe is decentralised; restoration planning is limited to within the area of control for each national transmission system operator (TSO). Although coordination of restorative actions between TSOs is encouraged, few agreements exist. This study proposes a decision support methodology for system operators and restoration planners for restoration of interconnected grids. Solutions to optimal and coordinated utilisation of tie lines (TLs) are proposed. The proposed tool facilitates collaboration between TSOs affected by wide area blackouts. The decision support tool allows to adaptively develop restoration strategies based on system conditions, available resources and operating constraints. Optimisation algorithms are proposed to determine the optimal utilisation of TLs and/or black-start (BS) units to crank non-BS units. Optimal power flow problems are formulated for utilisation of TLs. They offer solutions for neighbouring TSOs to determine the extent to which TLs can be used without violating constraints. The proposed decision support tool is tested with IEEE 39-bus system.

Technical Issues Associated with the Connection of Nuclear Power Plants to the National Electricity Transmission System via High-Voltage Direct Current Technology

This article highlights some of the key technical issues associated with the connection of large modern nuclear power plants (NPPs) to the national electricity transmission system via high-voltage direct current (HVDC) technology. The importance of the electricity system for such a connection is described. The need for reliable and secure supplies from the electricity grid to power the safety systems of the NPP is also discussed. Simulations carried out on the power system computer-aided design have highlighted the susceptibility of HVDC current source converter technology to commutation failure under a three-phase fault condition at the inverter when connected to a weak ac system. The work has also demonstrated the fault ride through the capability of the voltage source converter technology for the same scenario.

Transmission network expansion planning for the Colombian electrical system: Connecting the Ituango hydroelectric power plant

The hydroelectric power plant HidroItuango represents a major expansion for the Colombian electrical system (with a total capacity of 2400MW). This paper analyzes the possible interconnections and investments involved in connecting HidroItuango, in order to strengthen the Colombian national transmission system. A Mixed Binary Linear Programming (MBLP) model was used to solve the Multistage Transmission Network Expansion Planning (MTEP) problem of the Colombian electrical system, taking the N-1 safety criterion into account. The N-1 safety criterion indicates that the transmission system must be expanded so that the system will continue to operate properly if an outage in a system element (within a pre-defined set of contingencies) occurs. The use of a MBLP model guaranteed the convergence with existing classical optimization methods and the optimal solution for the MTEP using commercial solvers. Multiple scenarios for generation and demand were used to consider uncertainties within these parameters. The model was implemented using the algebraic modeling language AMPL and solved using the commercial solver CPLEX. The proposed model was then applied to the Colombian electrical system using the planning horizon of 2018–2025.

Incorporación de Dispositivos FACTS en el Sistema Nacional Interconectado

Ante el desarrollo de los diferentes proyectos de generación hidrotérmicos y los actuales problemas de capacidad de la red de transmisión, resulta necesario evaluar los reforzamientos del sistema de transmisión del país, de acuerdo al crecimiento de la demanda y el ingreso de los nuevos proyectos de generación. CENACE con el fin de cumplir con su rol de suministrar energía al país bajo las mejores condiciones de economía y calidad, analizó, de manera conjunta con la empresa norteamericana Quanta Technology, la factibilidad de incluir en el sistema de transmisión, dispositivos de respuesta rápida que garanticen la calidad y continuidad del suministro eléctrico.
 En este trabajo, a través de un análisis de contingencias en estado estable, se realiza la caracterización del Sistema Nacional Interconectado para el año 2017, con lo que se logra identificar las contingencias más críticas para el sistema. Posteriormente, mediante un análisis dinámico resulta posible categorizar las contingencias asociadas con problemas de estabilidad de voltaje. Estas contingencias son evaluadas de forma individual para determinar el requerimiento de compensación reactiva dinámica en diferentes zonas del SNI.