Various converters, generators, and other high power facilities are situated several kilometres away from metropolitan areas. Thus, numerous renewable energy sources with an interconnection between the generation and transmission technology require an efficient and high capacity system which entails the implementation of gas-insulated lines.
Gas-insulated lines (GIL) are a resourceful High Voltage (HV) transmission technology, which offers an alternative to traditional cables or overhead lines (OHL). Conventional cables are unable to provide adequate long-distance bulk power transmission as the ratings for voltage or useful power at the load aren’t sufficient in proportion to the line length. OHL with a lattice tower is a typical transmission method on shore with submarine Cross-linked Polyethylene (XLPE) cables or GIL utilised underground in challenging areas due to their flexibility and functional characteristics.
A 420/550 kV GIL representation comprising of a multiphase model and constant RLC values presents an adequate analysis of the system. Fundamentally, GIL offers encouraging results given the high-pressured insulation medium, skin effect and returning current. Furthermore, by utilising a common platform for the simulations, a fair comparison with various HV transmission alternatives is accomplished. Additionally, this investigation incorporates an overview of the overvoltage and recovery characteristics of the simulated GIL with an adequate power supply concerning the installation of a synchronous generator and wind turbine.
This research examines the economic factors with a distinctive focus on substantial investments made into offshore wind farms and GIL functioning in High Voltage Alternating Current (HVAC). The cost for this particular technical solution may provide an alternative to High Voltage Direct Current (HVDC) networks with Voltage Source Converters (HVDC-VSC) and submarine XLPE cables. The price per generating hour accumulates over time which reflects the total costs. Ultimately, the cost per unit is related to the demand.
Finally, the literature review includes technical data, background information and a verification process for the simulation results.
Table of Contents
1. Introduction
1.1. Renewable energy: Integration with GIL
1.2. Power transmission techniques: Roles and problems
1.2.1. Conventional transmission systems
1.2.2. GIL applications
1.3. Project goals and incentives
1.3.1. Aims and objectives
1.3.2. Project incentives
2. Literature review
2.1. Advantages of GIL
2.1.1. High-reliability standards
2.1.2. Low transmission losses
2.1.3. Low magnetic field ratings: GIL review
2.1.4. No ageing
2.2. Technical data and design of coaxial GIL: Background research
2.2.1. Case study: Second generation GIL at Palexpo exhibition hall
2.2.2. Design of a 420/550 kV GIL
3. Transmission characteristics of GIL
3.1. GIL: PSCAD model and simulations
3.1.1. EMTDCS/PSCAD: GIL simulation model
3.1.2. Simulation results: 0.7 and 0.8 power factor operation
3.1.3. 300km GIL results
3.1.4. Verification of the results
3.1.5. Loading conditions effect on GIL
3.1.6. Leading power factor effect on the GIL: PSCAD limitation
3.1.7. Lagging power factor effect on the GIL
4. Transmission technologies
4.1. Transmission characteristics of OHL
4.1.1. OHL: Design and implementation
4.2. Underground XLPE cables analysis
4.2.1. Comparison of transmission technologies
4.3. Wind turbine analysis and energisation: Overvoltage and transient recovery voltage (TRV) of GIL integrated with OHL
4.3.1. Design and specifications of GIL with a renewable wind source
4.4. HVDC technology: HVDC systems and economic analysis
4.4.1. Alternative voltage control strategy
4.4.2. Financial expenditures and Return on Investment (ROI) of transmission technologies
5. Conclusion
5.1. Review and recommendation
5.1.1. Content review: Key elements of the investigation
5.1.2. Transmission technology proposal
5.1.3. Future work
Project Goals and Scope
The primary goal of this research is to evaluate the practical feasibility of Gas-Insulated Lines (GIL) for long-distance, high-power transmission. By utilizing simulation software such as PSCAD and ATPDraw, the project investigates the technical performance, economic efficiency, and environmental integration of GIL systems compared to traditional alternatives like Overhead Lines (OHL) and underground XLPE cables, specifically in the context of connecting offshore renewable energy sources to bulk power grids.
- Simulation and technical modeling of GIL systems using PSCAD and ATPDraw.
- Economic comparison of GIL against HVDC and traditional HVAC transmission methods.
- Analysis of GIL performance under various load conditions and transmission distances.
- Evaluation of overvoltage and transient recovery characteristics for grid integration.
- Proposing optimal transmission solutions for large-scale renewable projects, such as those in North Wales.
Excerpt from the Book
1.2.2. GIL applications
The first generation GIL application consists of pure sulphur hexafluoride (SF6) for insulation in contrast to the second generation, developed to reduce costs and improve efficiency. The second generation of GIL entails a coaxial, aluminium conductor for electrical transmission and an insulating-gas mixture of 20 % SF6, and 80 % nitrogen (N2) [6]. The gas insulation is under a substantial amount of pressure, specified in more detail in chapter 2 to maintain a compact and efficient transmission. The setup operates with a large outer aluminium coated enclosure for the gas compounds and a protection layer.
Previously, the insulation of traditional cables comprises of an XLPE sheath or paper with oil to reduce the losses and achieve a higher useful power rating at the load. SF6 is an insulation gas for substations and GIL due to its dielectric strength. The main issue concerning SF6 as an insulator is that it’s very harmful. Its global warming potential (GWP) value is 23,900 times that of carbon dioxide (CO2) over a 100-year time horizon [7]. Alternative gas insulation compounds are researched to compromise for hindrances concerning the high GWP.
The general public negatively views OHL due to its visual impact. Lattice transmission towers operate with two electric circuits and protection cables for reliability purposes. Several economic factors such as tourism and house prices are affected by these design features. A long-term and feasible alternative is underground GIL.
GIL has relatively low losses in comparison to other transmission procedures. The resistance, inductance, and capacitance per phase are relational to the space between the cross-sectional area of the conductor and the enclosure of the pipe. A relatively small capacitance is also a feature for the GIL, as no reactive compensation is necessary for transmission lengths of 100 km [8]. The simulations conducted reflect these particular characteristics. The most extensive operational GIL is 12.5 km, constructed by Siemens to deliver HV transmission from a vast hydropower plant in Xiloudu, Southwest China [9]. The GIL technology installation is enclosed within the dam which entails a vertical design [9]. Evidently, the generated power flows directly through the GIL for reliability and future development purposes. The hydropower plant deals with real-time peaks in demand for energy, and gas insulated transmission technology is an exceptional candidate for this studied case.
Summary of Chapters
1. Introduction: Discusses the integration of renewable energy, specifically offshore wind, into power networks and the role of GIL as a potential transmission solution.
2. Literature review: Explores the advantages of GIL, including high reliability, low transmission losses, and minimal environmental impact, while providing technical background research.
3. Transmission characteristics of GIL: Details the PSCAD modeling and simulation process, covering load effects, power factor operation, and results verification for various transmission distances.
4. Transmission technologies: Provides a comparative analysis of OHL, XLPE cables, and GIL, including wind turbine integration, overvoltage performance, and a comprehensive economic analysis.
5. Conclusion: Summarizes the key findings of the investigation and provides a proposal for utilizing HVAC GIL in the context of future energy projects.
Keywords
Gas-Insulated Lines, GIL, HVAC, PSCAD, Offshore Wind, Power Transmission, Renewable Energy, Overvoltage, Transient Recovery Voltage, Economic Analysis, XLPE Cables, Overhead Lines, Transmission Efficiency, Grid Integration, Simulation Modeling.
Frequently Asked Questions
What is the core focus of this research project?
The research evaluates the practicality of using Gas-Insulated Lines (GIL) for long-distance, high-capacity power transmission, particularly to connect offshore wind farms to the national grid.
What are the primary transmission technologies discussed?
The project compares Gas-Insulated Lines (GIL) with traditional Overhead Lines (OHL) and underground Cross-linked Polyethylene (XLPE) cables.
What is the main objective of the simulation models?
The goal is to determine the performance, transmission efficiency, and maximum feasible distance of GIL systems under various load and power factor conditions using software like PSCAD and ATPDraw.
Which scientific methods are employed for the analysis?
The work utilizes numerical simulation models, mathematical calculations for resistance and impedance, and iterative standard deviation techniques to compare active and reactive power characteristics.
What does the main body of the report cover?
It covers literature reviews on GIL advantages, technical design data, simulation results regarding load effects and power factors, transmission technology comparisons, and a financial ROI analysis.
How can this research be characterized by its keywords?
The work is characterized by terms such as GIL, HVAC, power transmission, offshore wind, PSCAD simulation, economic analysis, and renewable energy integration.
What are the specific findings regarding GIL and the Ferranti effect?
The research observes the Ferranti effect in the GIL during light load conditions, which influences the reactive power consumption and requires careful load configuration management.
What role does the G59 regulation play in the study?
G59 regulations are used to set the limits for overvoltage protection and transient recovery voltage, ensuring that the GIL system remains compliant within defined operational voltage thresholds.
How does the cost of GIL compare to OHL in this study?
The study notes that while OHL is the most economical transmission method for dryland, GIL provides a more efficient and visually compact solution for metropolitan or sensitive marine environments despite higher initial costs.
What is the proposal for the Isle of Anglesey?
The research proposes utilizing HVAC GIL as a preferred solution for energy transmission projects in the Isle of Anglesey to minimize visual impact and achieve higher efficiency compared to conventional cable alternatives.
- Quote paper
- Llion Stephen (Author), 2018, Gas-insulated lines for HVAC transmission for long distance bulk-power transmission (HVAC), Munich, GRIN Verlag, https://www.grin.com/document/437194
