This document describes a study analyzing how cable ampacity is affected by different backfill configurations using finite element modeling. It begins by reviewing existing methods for calculating external thermal resistance from standards like IEEE and extensions by other researchers. The finite element method allows modeling situations with varying soil thermal resistivities not addressed by standards. Results show ampacity is highly sensitive to soil thermal properties. The study then analyzes effects on ampacity from varying backfill quantity, shape, location and engineered backfill using finite element modeling to better understand impacts in non-standardized situations.
Underground cables consist of one or more insulated conductors surrounded by protective layers. They are used to transmit electric power underground, which ensures continuous power supply with less maintenance compared to overhead lines. Common types include low, high, and extra high tension cables. Cables have conducting cores insulated and surrounded by a metallic sheath, bedding, armouring and serving for protection. Screened and belted cables are used for 3-phase underground transmission up to 66kV, while pressure cables are used above 66kV.
1. The document discusses measurement of DC resistivity, including specifications for specimen shape and electrode arrangement, materials used for electrodes, and different measuring cell configurations.
2. It also covers partial discharge measurement, defining terms like partial discharge and describing the partial discharge phenomenon in insulation with voids.
3. Breakdown mechanisms in gases, liquids and solids are outlined, focusing on ionization processes in gases which can lead to electrical breakdown at high voltages.
This document outlines standards and procedures for transmission line route surveys. It discusses responsibilities, survey methods, drawings, and other documentation required. Some key points:
- The contractor is responsible for selecting the transmission line route based on criteria like minimum length, cost, and environmental impact. They must perform preliminary and detailed surveys.
- Surveying methods include establishing angle points, profiling the terrain, and noting obstacles. Data is recorded on plan and profile drawings.
- Drawings include general layouts, detailed plans and profiles, and crossings. Profile stationing starts from the power source.
- The contractor must ensure accurate structure placement within specified tolerances based on the survey data.
The document provides a summary of the single line diagram of the 132kv S/S PGIA substation. It has 3 incoming 132kv lines from the 400/220kv Sarojini Nagar substation and 1 outgoing 132kv line. The incoming lines pass through lightning arrestors and insulated discs before connecting to the gantry and circuit breakers. The line then passes through potential transformers and current transformers before connecting to the main bus bar. From the bus bar, the line is distributed to the 132kv bay and transformers through isolators. The substation also includes a 33kv substation with 2 40MVA transformers, 33kv bus bars, and bays. It describes the purpose of components like capacitor banks, isol
The document discusses busbar protection, including the need for busbar protection, types of busbar protections like high impedance, medium impedance and low impedance protections. It describes the requirements of busbar protection like short tripping time and stable operation during external faults. The document discusses different busbar arrangements and applications of numerical busbar protection systems like RADSS. It provides examples of busbar protection schemes for different bus configurations. The document also includes excerpts from technical manuals providing recommendations on busbar protection in substations.
The Presentation represents one of the electromagnatic effect on transmission line (The skin effect), other being the proximity effect.
The Following topics are covered :
1.Defination
2,Cause
3.Formula
4.Skin Depth
5.Mitigation Techniques.
The document discusses underground power cables. It describes the components of underground cables including conductors, insulation, metallic sheathing, bedding, armoring and serving. The main types of underground cables are discussed - solid cables like belted and screened cables used up to 66kV, and pressurized oil and gas cables used at higher voltages. Methods of laying cables underground include direct burying, draw-in systems using ducts, and solid systems within troughs. Underground cables have advantages over overhead lines like better appearance and reliability, but also challenges like higher installation costs and fault localization difficulties.
A private company is building a new factory requiring 1150 kVA of power. The company will connect to a 36 kV distribution network with a short circuit current of 15.3 kA and rated operational current of 525 A at 31.5 kV. A new indoor transformer substation will include a load break switch incoming feeder, circuit breaker outgoing feeder, circuit breaker for customer isolation and protection, metering cubicle, and transformer protection cubicle with circuit breaker. The transformer will be selected as 1600 kVA, 31.5/0.4 kV based on the power requirements. A single line diagram of the substation will be drawn showing all equipment ratings.
Underground cables consist of one or more insulated conductors surrounded by protective layers. They are used to transmit electric power underground, which ensures continuous power supply with less maintenance compared to overhead lines. Common types include low, high, and extra high tension cables. Cables have conducting cores insulated and surrounded by a metallic sheath, bedding, armouring and serving for protection. Screened and belted cables are used for 3-phase underground transmission up to 66kV, while pressure cables are used above 66kV.
1. The document discusses measurement of DC resistivity, including specifications for specimen shape and electrode arrangement, materials used for electrodes, and different measuring cell configurations.
2. It also covers partial discharge measurement, defining terms like partial discharge and describing the partial discharge phenomenon in insulation with voids.
3. Breakdown mechanisms in gases, liquids and solids are outlined, focusing on ionization processes in gases which can lead to electrical breakdown at high voltages.
This document outlines standards and procedures for transmission line route surveys. It discusses responsibilities, survey methods, drawings, and other documentation required. Some key points:
- The contractor is responsible for selecting the transmission line route based on criteria like minimum length, cost, and environmental impact. They must perform preliminary and detailed surveys.
- Surveying methods include establishing angle points, profiling the terrain, and noting obstacles. Data is recorded on plan and profile drawings.
- Drawings include general layouts, detailed plans and profiles, and crossings. Profile stationing starts from the power source.
- The contractor must ensure accurate structure placement within specified tolerances based on the survey data.
The document provides a summary of the single line diagram of the 132kv S/S PGIA substation. It has 3 incoming 132kv lines from the 400/220kv Sarojini Nagar substation and 1 outgoing 132kv line. The incoming lines pass through lightning arrestors and insulated discs before connecting to the gantry and circuit breakers. The line then passes through potential transformers and current transformers before connecting to the main bus bar. From the bus bar, the line is distributed to the 132kv bay and transformers through isolators. The substation also includes a 33kv substation with 2 40MVA transformers, 33kv bus bars, and bays. It describes the purpose of components like capacitor banks, isol
The document discusses busbar protection, including the need for busbar protection, types of busbar protections like high impedance, medium impedance and low impedance protections. It describes the requirements of busbar protection like short tripping time and stable operation during external faults. The document discusses different busbar arrangements and applications of numerical busbar protection systems like RADSS. It provides examples of busbar protection schemes for different bus configurations. The document also includes excerpts from technical manuals providing recommendations on busbar protection in substations.
The Presentation represents one of the electromagnatic effect on transmission line (The skin effect), other being the proximity effect.
The Following topics are covered :
1.Defination
2,Cause
3.Formula
4.Skin Depth
5.Mitigation Techniques.
The document discusses underground power cables. It describes the components of underground cables including conductors, insulation, metallic sheathing, bedding, armoring and serving. The main types of underground cables are discussed - solid cables like belted and screened cables used up to 66kV, and pressurized oil and gas cables used at higher voltages. Methods of laying cables underground include direct burying, draw-in systems using ducts, and solid systems within troughs. Underground cables have advantages over overhead lines like better appearance and reliability, but also challenges like higher installation costs and fault localization difficulties.
A private company is building a new factory requiring 1150 kVA of power. The company will connect to a 36 kV distribution network with a short circuit current of 15.3 kA and rated operational current of 525 A at 31.5 kV. A new indoor transformer substation will include a load break switch incoming feeder, circuit breaker outgoing feeder, circuit breaker for customer isolation and protection, metering cubicle, and transformer protection cubicle with circuit breaker. The transformer will be selected as 1600 kVA, 31.5/0.4 kV based on the power requirements. A single line diagram of the substation will be drawn showing all equipment ratings.
Chapter 4 mechanical design of transmission linesfiraoltemesgen1
This chapter discusses the mechanical design of transmission lines. It covers various topics such as types of conductors, line supports, spacing between conductors, and sag-tension calculations. The key conductors mentioned are copper, aluminum, and steel. Wooden poles, steel tubular poles, reinforced concrete poles, and steel towers are described as the main types of line supports. The document also discusses the effects of wind and ice loading on transmission lines. Sag-tension calculations are explained using catenary curve equations.
(1) A symmetrical fault occurs on bus 3 of a 3-bus system.
(2) The Thevenin equivalent impedance is calculated to be j0.21 p.u.
(3) For a fault impedance of j0.19 p.u., the fault current is calculated to be -j2.5 p.u. and the post-fault bus voltages are determined.
(4) For a bolted fault with zero impedance, the fault current is -j4.76 p.u. and the post-fault bus voltages and line currents are found.
Underground cables have several key components and requirements:
- Conductors are made of stranded copper or aluminum to provide flexibility and high conductivity. Insulation provides voltage isolation and comes in materials like paper, rubber, or mineral compounds.
- Cables include protective layers like metallic sheathing to prevent damage from the environment, bedding to protect the sheath, and armoring for mechanical protection during laying.
- Cables are classified based on voltage range as low, high, extra high tension etc. Common cable types include belted cables below 11kV, screened cables from 22kV-66kV, and pressure cables over 66kV which use oil or gas insulation.
This document discusses earthing systems for cable screens in power lines with voltages of 66kV or greater. It describes two main types of screen earthing diagrams: rigid earthing systems and special earthing systems. Rigid earthing systems directly connect all three phase screens together and to earth, allowing screen currents but maintaining voltages close to zero. Special earthing systems aim to prevent or cancel screen currents to reduce losses, requiring screens to withstand small permanent voltages and current surges. One such system described is the cross bonded system, which divides the line into sections and uses crossed screen connections between sections to reduce induced electromotive forces.
Calidad del servicio en sistemas electricos de potenciaEduardo Soracco
El documento habla sobre la calidad del servicio eléctrico. Explica que para evaluar la calidad se consideran variables como interrupciones, niveles de tensión, forma de onda y frecuencia. También describe las causas más comunes de perturbaciones como armónicos, huecos de tensión, flicker y desequilibrios. Finalmente, señala posibles causas de una mala calidad del servicio como falta de mantenimiento e inversión en los sistemas eléctricos.
Underground cables consist of one or more conductors surrounded by insulation and protective covering. They are buried directly in the ground or in ducts to protect from external disturbances. Underground cables have advantages like better appearance and reduced faults but also higher maintenance costs and longer repair times for faults. Cables use various materials for insulation like rubber, paper, PVC and XLPE, with different properties suitable for different voltages. Cables are classified based on voltage as low, high, extra high tension cables. Faults like open circuits, short circuits and earth faults can occur and be detected using a megger. The maximum length of underground cables is limited by higher capacitance causing increased line charging currents at higher voltages.
Cable Conductor Sizing for Minimum Life Cycle CostLeonardo ENERGY
Energy prices are high and expected to rise. All CO2 emissions are being scrutinized by regulators as well as by public opinion. As a result, energy management has become a key factor in almost every business. To get the most out of each kilowatt-hour, appliances must be carefully evaluated for their energy efficiency.
It is an often overlooked fact that electrical energy gets lost in both end-use and in the supply system (cables, busbars, transformers, etc.). Every cable has resistance, so part of the electrical energy that it carries is dissipated as heat and is lost.
Such energy losses can be reduced by increasing the cross section of the copper conductor in a cable or busbar. Obviously, the conductor size cannot be increased endlessly. The objective should be the economic and/or environmental optimum. What is the optimal cross section necessary to maximize the Return on Investment (ROI) and minimize the Net Present Value (NPV) and/or the Life Cycle Cost (LCC)?
This paper will demonstrate that the maximizing of the ROI results in a cross section that is far larger than which technical standards prescribe. Those standards are based entirely on safety and certain power quality aspects. This means there is room for improvement—a great deal of improvement in fact.
The document discusses the construction of underground cables. It describes the various parts of an underground cable including conductors, insulation, metallic sheath, bedding, armoring, and serving. It explains the purpose and materials used for each part. Common insulating materials like rubber, impregnated paper, PVC, and XLPE are also explained. Underground cables have advantages like better appearance, lower maintenance costs and reduced faults compared to overhead cables, but higher installation costs.
Este documento describe los pasos para modelar una malla eléctrica de 18 x 6 metros usando el programa ETAP. Primero, se crea la malla en AutoCAD con varillas de cobre desnudo N. 2/0. Luego, se exporta la malla a ETAP donde se definen los tipos de conductor y varilla. Finalmente, se editan los detalles de la malla y varillas, y se calculan los voltajes de toque y paso para verificar que cumplen con la norma IEEE-80.
OPTIMAL PLACEMENT AND SIZING OF CAPACITOR BANKS BASED ON VOLTAGE PROFILE AND ...Prashanta Sarkar
This document summarizes a thesis on optimally placing and sizing capacitor banks in a radial distribution system to improve voltage profile and reduce losses, and the effects of adding distributed generation. The study formulates an objective function to minimize losses and maximize voltages. Optimal capacitor placement is performed using genetic algorithms in ETAP software. Manual placement of capacitor banks is also evaluated. Adding distributed generation along with capacitors is found to further improve voltages and reduce losses compared to capacitors alone. The conclusion discusses benefits of compensation and future work on switching technologies and soft computing techniques for optimization.
This document discusses the key components and design considerations for extra high voltage (EHV) AC transmission lines. It covers:
1. The main components of transmission lines including conductors, earth wires, insulators, towers, and hardware.
2. The design methodology which involves calculating loads from climatic conditions, reliability requirements, and safety factors before designing each component.
3. Factors involved in selecting the transmission voltage level based on the power level, line length, voltage regulation needs, and costs.
4. The types of transmission towers used for different line angles and situations like river crossings.
5. Design of the tower structure including height, base width, cross arm length based
Régimen de conexión a tierra, (ICA-Procobre, Ago. 2016)Efren Franco
El documento presenta información sobre los diferentes regímenes de conexión a tierra que pueden implementarse en sistemas eléctricos. Describe los tres regímenes principales (TN, TT y IT), explicando sus características, modos de operación ante fallas y variantes. También incluye definiciones de términos relacionados como conductor neutro, conductor de protección, electrodo de puesta a tierra y puente de unión.
Modern underground power cables are sophisticated assemblies of insulators, conductors and protective materials. Within these components are sensors, which enable cable operators to monitor conditions along the cable in real time.
The condition of the cable insulation is usually monitored through the following two main methods:
Loss tangent measurements
Partial discharge (PD) measurements
Underground cables have several advantages over overhead cables including better appearance, reduced damage from external factors like storms and lighting, lower maintenance costs, and fewer faults. Underground cables consist of one or more insulated conductors surrounded by protective layers. Key components include the conductor, insulation like paper or rubber, a metallic sheath, bedding, armor for protection, and an outer serving. Different types are used for various voltage applications up to extra high voltage cables over 33kV. Selection depends on factors like the number of cores needed, insulation material, and whether solid or pressure cables are required.
Since the loads having the trends towards growing density. This requires the better appearance, rugged construction, greater service reliability and increased safety. An underground cable essentially consists of one or more conductors covered with suitable insulation and surrounded by a protecting cover. The interference from external disturbances like storms, lightening, ice, trees etc. should be reduced to achieve trouble free service. The cables may be buried directly in the ground, or may be installed in ducts buried in the ground.
This document discusses insulation coordination for electrical systems. It defines insulation coordination as selecting suitable insulation levels for system components and arranging them rationally. The goals of insulation coordination are to ensure insulation can withstand normal and abnormal stresses and efficiently discharge over voltages. It also discusses determining live insulation levels, equipment BIL levels, and selecting lightning arrestors. Various insulation levels for lines and equipment are recommended based on system voltage.
15 years of experience stator ground fault protectionmichaeljmack
The document discusses different methods for 100% stator ground fault protection on generators based on 15 years of experience. It describes conventional 59G protection that only covers 90-95% of the stator, as well as 3rd harmonic schemes that can provide full coverage but have limitations. Subharmonic injection was also used in Europe and provides full coverage independently of generator loading. While 3rd harmonic schemes require testing the generator's harmonic signature, subharmonic injection is preferable as it works regardless of loading and can detect faults offline or throughout the entire winding.
Electromagnetic analysis of submarine umbilical cables with complex configura...thinknice
This document summarizes electromagnetic analyses of different configurations of integrated production umbilical cables. Umbilical cables can have multiple independent power circuits and steel tubes. Three configurations (A, B, C) are analyzed using a combined 2D finite element and transposition methodology to evaluate performance considering load terminal voltages and induced voltages. Configuration B, where each power circuit rotates around its own center, has the best performance with balanced terminal voltages and minimized induction effects along the cable length.
Design methodology for undersea umbilical cablesthinknice
This document describes a methodology for designing umbilical cables used in undersea applications. It presents a design nomograph and simple formulas as preliminary design aids. The methodology involves specifying operational parameters, conducting a preliminary design, defining the cable cross-section, analyzing the cable suspension, using computer-aided design, and prototype testing. Key steps include determining armor area, helical wire coverage, torque and stress balance, and using linear cable equilibrium equations. The goal is to satisfy strength, deformation, and handling requirements through an iterative design process.
Chapter 4 mechanical design of transmission linesfiraoltemesgen1
This chapter discusses the mechanical design of transmission lines. It covers various topics such as types of conductors, line supports, spacing between conductors, and sag-tension calculations. The key conductors mentioned are copper, aluminum, and steel. Wooden poles, steel tubular poles, reinforced concrete poles, and steel towers are described as the main types of line supports. The document also discusses the effects of wind and ice loading on transmission lines. Sag-tension calculations are explained using catenary curve equations.
(1) A symmetrical fault occurs on bus 3 of a 3-bus system.
(2) The Thevenin equivalent impedance is calculated to be j0.21 p.u.
(3) For a fault impedance of j0.19 p.u., the fault current is calculated to be -j2.5 p.u. and the post-fault bus voltages are determined.
(4) For a bolted fault with zero impedance, the fault current is -j4.76 p.u. and the post-fault bus voltages and line currents are found.
Underground cables have several key components and requirements:
- Conductors are made of stranded copper or aluminum to provide flexibility and high conductivity. Insulation provides voltage isolation and comes in materials like paper, rubber, or mineral compounds.
- Cables include protective layers like metallic sheathing to prevent damage from the environment, bedding to protect the sheath, and armoring for mechanical protection during laying.
- Cables are classified based on voltage range as low, high, extra high tension etc. Common cable types include belted cables below 11kV, screened cables from 22kV-66kV, and pressure cables over 66kV which use oil or gas insulation.
This document discusses earthing systems for cable screens in power lines with voltages of 66kV or greater. It describes two main types of screen earthing diagrams: rigid earthing systems and special earthing systems. Rigid earthing systems directly connect all three phase screens together and to earth, allowing screen currents but maintaining voltages close to zero. Special earthing systems aim to prevent or cancel screen currents to reduce losses, requiring screens to withstand small permanent voltages and current surges. One such system described is the cross bonded system, which divides the line into sections and uses crossed screen connections between sections to reduce induced electromotive forces.
Calidad del servicio en sistemas electricos de potenciaEduardo Soracco
El documento habla sobre la calidad del servicio eléctrico. Explica que para evaluar la calidad se consideran variables como interrupciones, niveles de tensión, forma de onda y frecuencia. También describe las causas más comunes de perturbaciones como armónicos, huecos de tensión, flicker y desequilibrios. Finalmente, señala posibles causas de una mala calidad del servicio como falta de mantenimiento e inversión en los sistemas eléctricos.
Underground cables consist of one or more conductors surrounded by insulation and protective covering. They are buried directly in the ground or in ducts to protect from external disturbances. Underground cables have advantages like better appearance and reduced faults but also higher maintenance costs and longer repair times for faults. Cables use various materials for insulation like rubber, paper, PVC and XLPE, with different properties suitable for different voltages. Cables are classified based on voltage as low, high, extra high tension cables. Faults like open circuits, short circuits and earth faults can occur and be detected using a megger. The maximum length of underground cables is limited by higher capacitance causing increased line charging currents at higher voltages.
Cable Conductor Sizing for Minimum Life Cycle CostLeonardo ENERGY
Energy prices are high and expected to rise. All CO2 emissions are being scrutinized by regulators as well as by public opinion. As a result, energy management has become a key factor in almost every business. To get the most out of each kilowatt-hour, appliances must be carefully evaluated for their energy efficiency.
It is an often overlooked fact that electrical energy gets lost in both end-use and in the supply system (cables, busbars, transformers, etc.). Every cable has resistance, so part of the electrical energy that it carries is dissipated as heat and is lost.
Such energy losses can be reduced by increasing the cross section of the copper conductor in a cable or busbar. Obviously, the conductor size cannot be increased endlessly. The objective should be the economic and/or environmental optimum. What is the optimal cross section necessary to maximize the Return on Investment (ROI) and minimize the Net Present Value (NPV) and/or the Life Cycle Cost (LCC)?
This paper will demonstrate that the maximizing of the ROI results in a cross section that is far larger than which technical standards prescribe. Those standards are based entirely on safety and certain power quality aspects. This means there is room for improvement—a great deal of improvement in fact.
The document discusses the construction of underground cables. It describes the various parts of an underground cable including conductors, insulation, metallic sheath, bedding, armoring, and serving. It explains the purpose and materials used for each part. Common insulating materials like rubber, impregnated paper, PVC, and XLPE are also explained. Underground cables have advantages like better appearance, lower maintenance costs and reduced faults compared to overhead cables, but higher installation costs.
Este documento describe los pasos para modelar una malla eléctrica de 18 x 6 metros usando el programa ETAP. Primero, se crea la malla en AutoCAD con varillas de cobre desnudo N. 2/0. Luego, se exporta la malla a ETAP donde se definen los tipos de conductor y varilla. Finalmente, se editan los detalles de la malla y varillas, y se calculan los voltajes de toque y paso para verificar que cumplen con la norma IEEE-80.
OPTIMAL PLACEMENT AND SIZING OF CAPACITOR BANKS BASED ON VOLTAGE PROFILE AND ...Prashanta Sarkar
This document summarizes a thesis on optimally placing and sizing capacitor banks in a radial distribution system to improve voltage profile and reduce losses, and the effects of adding distributed generation. The study formulates an objective function to minimize losses and maximize voltages. Optimal capacitor placement is performed using genetic algorithms in ETAP software. Manual placement of capacitor banks is also evaluated. Adding distributed generation along with capacitors is found to further improve voltages and reduce losses compared to capacitors alone. The conclusion discusses benefits of compensation and future work on switching technologies and soft computing techniques for optimization.
This document discusses the key components and design considerations for extra high voltage (EHV) AC transmission lines. It covers:
1. The main components of transmission lines including conductors, earth wires, insulators, towers, and hardware.
2. The design methodology which involves calculating loads from climatic conditions, reliability requirements, and safety factors before designing each component.
3. Factors involved in selecting the transmission voltage level based on the power level, line length, voltage regulation needs, and costs.
4. The types of transmission towers used for different line angles and situations like river crossings.
5. Design of the tower structure including height, base width, cross arm length based
Régimen de conexión a tierra, (ICA-Procobre, Ago. 2016)Efren Franco
El documento presenta información sobre los diferentes regímenes de conexión a tierra que pueden implementarse en sistemas eléctricos. Describe los tres regímenes principales (TN, TT y IT), explicando sus características, modos de operación ante fallas y variantes. También incluye definiciones de términos relacionados como conductor neutro, conductor de protección, electrodo de puesta a tierra y puente de unión.
Modern underground power cables are sophisticated assemblies of insulators, conductors and protective materials. Within these components are sensors, which enable cable operators to monitor conditions along the cable in real time.
The condition of the cable insulation is usually monitored through the following two main methods:
Loss tangent measurements
Partial discharge (PD) measurements
Underground cables have several advantages over overhead cables including better appearance, reduced damage from external factors like storms and lighting, lower maintenance costs, and fewer faults. Underground cables consist of one or more insulated conductors surrounded by protective layers. Key components include the conductor, insulation like paper or rubber, a metallic sheath, bedding, armor for protection, and an outer serving. Different types are used for various voltage applications up to extra high voltage cables over 33kV. Selection depends on factors like the number of cores needed, insulation material, and whether solid or pressure cables are required.
Since the loads having the trends towards growing density. This requires the better appearance, rugged construction, greater service reliability and increased safety. An underground cable essentially consists of one or more conductors covered with suitable insulation and surrounded by a protecting cover. The interference from external disturbances like storms, lightening, ice, trees etc. should be reduced to achieve trouble free service. The cables may be buried directly in the ground, or may be installed in ducts buried in the ground.
This document discusses insulation coordination for electrical systems. It defines insulation coordination as selecting suitable insulation levels for system components and arranging them rationally. The goals of insulation coordination are to ensure insulation can withstand normal and abnormal stresses and efficiently discharge over voltages. It also discusses determining live insulation levels, equipment BIL levels, and selecting lightning arrestors. Various insulation levels for lines and equipment are recommended based on system voltage.
15 years of experience stator ground fault protectionmichaeljmack
The document discusses different methods for 100% stator ground fault protection on generators based on 15 years of experience. It describes conventional 59G protection that only covers 90-95% of the stator, as well as 3rd harmonic schemes that can provide full coverage but have limitations. Subharmonic injection was also used in Europe and provides full coverage independently of generator loading. While 3rd harmonic schemes require testing the generator's harmonic signature, subharmonic injection is preferable as it works regardless of loading and can detect faults offline or throughout the entire winding.
Electromagnetic analysis of submarine umbilical cables with complex configura...thinknice
This document summarizes electromagnetic analyses of different configurations of integrated production umbilical cables. Umbilical cables can have multiple independent power circuits and steel tubes. Three configurations (A, B, C) are analyzed using a combined 2D finite element and transposition methodology to evaluate performance considering load terminal voltages and induced voltages. Configuration B, where each power circuit rotates around its own center, has the best performance with balanced terminal voltages and minimized induction effects along the cable length.
Design methodology for undersea umbilical cablesthinknice
This document describes a methodology for designing umbilical cables used in undersea applications. It presents a design nomograph and simple formulas as preliminary design aids. The methodology involves specifying operational parameters, conducting a preliminary design, defining the cable cross-section, analyzing the cable suspension, using computer-aided design, and prototype testing. Key steps include determining armor area, helical wire coverage, torque and stress balance, and using linear cable equilibrium equations. The goal is to satisfy strength, deformation, and handling requirements through an iterative design process.
Nexans Norway has extensive experience in designing and manufacturing submarine power cables. They offer cables from 6 to 525 kV with insulation systems tailored for AC or DC applications. Their factory is designed to produce long cable lengths and they have connected areas over long distances and deep waters. Nexans Norway combines different elements in one cable to suit various needs and has decades of experience supplying cables for offshore connections.
This document summarizes a lecture on subsea umbilicals and power cables. It discusses BPP-TECH, a company that provides engineering services to the offshore industry. It then describes subsea umbilicals and power cables, how technological advances have pushed development into deeper waters, and the engineering challenges involved. Finally, it outlines steps taken to mitigate risk, advances in design tools and materials, and conclusions on the importance of reliability for subsea systems.
Study: The Future of VR, AR and Self-Driving CarsLinkedIn
We asked LinkedIn members worldwide about their levels of interest in the latest wave of technology: whether they’re using wearables, and whether they intend to buy self-driving cars and VR headsets as they become available. We asked them too about their attitudes to technology and to the growing role of Artificial Intelligence (AI) in the devices that they use. The answers were fascinating – and in many cases, surprising.
This SlideShare explores the full results of this study, including detailed market-by-market breakdowns of intention levels for each technology – and how attitudes change with age, location and seniority level. If you’re marketing a tech brand – or planning to use VR and wearables to reach a professional audience – then these are insights you won’t want to miss.
Artificial intelligence (AI) is everywhere, promising self-driving cars, medical breakthroughs, and new ways of working. But how do you separate hype from reality? How can your company apply AI to solve real business problems?
Here’s what AI learnings your business should keep in mind for 2017.
A Study on Thermal behavior of Nano film as thermal interface layerIJASCSE
Increase in thermal design power and re-duce in manufacturing cost of the processor chip has pushes the need for high performance and durable test fixture design in future. Test fixture with efficient themal management has lowest resistance possible to maintain the accuracy of the device temperature when it makes contact with processor chip’s silicon during test. High thermal conductivity and mechanical relia-bility of text fixures are desired for high volume test environment. Nano film materials such as Aluminum Titanium Nitride (AlTiN), Titanium carbide (TiC), Ti-tanium on Titanium nitride (Ti on TiN), Titanium ni-tride on Titanium (TiN on Ti) and Aluminum(III) Ox-ide (Al2O3) are coated over copper substrates by Fil-tered Cathodic Vacuum Arc (FCVA) deposition method and tested for their thermal conductivity behavior for high volume test (HVM) environment. Thermal con-ductivity of the prepared films is tested by using the ASTM 5470 Thermal Interface Material (TIM) Tester. Titanium on Titanium nitride (Ti on TiN) and Alumi-num (III) Oxide (Al2O3) observed with highest thermal conductivity of 117.68 W/mk and 128.34 W/mk respec-tively among the prepared nano thin films. Thickness of the film and stack configuration influenced the thermal conductivity of the prepared film.
The document discusses capacitance variation in MEMS capacitors based on plate area, distance between plates, and different dielectric materials. It outlines the research significance, methodology, experimental details, results and discussion, and conclusion. The results show that capacitance increases with larger plate area, smaller distance between plates, and dielectric materials with higher relative dielectric constants. The capacitance variation can be utilized in applications such as wireless communications, sensing, and electronics.
This document summarizes research on modeling the thermal conductivity of 2D silicon-germanium nanocomposites. The researchers developed a computational approach using finite element analysis and the heat conduction equation to calculate effective thermal conductivity. They accounted for interfacial thermal resistance and size-dependent phonon mean free paths. The model was used to study the effects of inclusion size, shape, and random distribution on thermal conductivity. Predictions agreed well with results from the Boltzmann transport equation and effective medium approximation models. The proposed approach can efficiently handle complex inclusion geometries and distributions.
This document summarizes an experiment to measure the out-of-plane thermal conductivity of flexible substrate materials like polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET). A steady-state method is used where a heat flux is applied through one copper block in contact with the substrate, and the temperature difference across the substrate is measured. Thermal conductivity values are determined from the temperature differences and heat fluxes for substrates of varying thicknesses. The results indicate low thermal conductivity for flexible substrates, which could challenge thermal management in flexible electronics due to limited heat spreading and lack of active cooling options.
Potential enhancement of thermoelectric energy conversion in cobaltite superl...Anastasios Englezos
This document is a master's thesis submitted by Tasos Englezos investigating the potential enhancement of thermoelectric energy conversion in cobaltite oxide superlattices. The thesis aims to grow superlattices composed of alternating layers of NaxCoO3 and Ca3Co4O9 using pulsed laser deposition, as both materials show promise for thermoelectric applications but also have limitations. Characterization of the superlattices shows the structures maintain crystalline coherence while electrical and thermal properties are preserved at a good level. Further measurements of thermal conductivity are needed to determine if the superlattice approach reduces thermal conductivity and thereby improves thermoelectric efficiency in these cobaltite oxides.
Improvement of dielectric strength and properties of cross-linked polyethyleneIJECEIAES
Power cables insulated with cross-linked polyethylene (XLPE) have been utilized worldwide for distribution and transmission networks. There are several advantages for this type of insulation; it has better electrical, thermal, and mechanical properties compared to other types of insulation in medium and high voltage networks. Many studies aimed to improve the XLPE characteristics through introducing nano fillers to the XLPE matrix. Therefore, this paper investigates the AC (HV) breakdown voltage (dielectric strength) of XLPE after adding nano-sized zeolite (Z) fillers with various concentrations of 1 wt%, 3 wt%, 5 wt% and 7 wt%. The dielectric strength is tested in different temperatures of 30 ⁰C and 250 ⁰C. Additionally, it was tested in low and high salty wet conditions. The dielectric strength of the XLPE has been enhanced by inducing the Z nano filler. The results of the tests were used to train the artificial neural network (ANN) to calculate the dielectric strength of XLPE composites with different concentrations of nano Z filler under different weathering conditions. Thermogravimetric analysis, tensile strength, and elongation at break tests were applied to check the thermal and mechanical characteristics of the samples. Experimental findings show that the optimum concentration of nano Z is 3.64 wt% to enhance the electrical, thermal, and mechanical properties.
Experimental Investigation of Flow Pattern on Rectangular Fin Arrays under Na...IJMER
Abstract: In Natural convection heat transfer with the help of fin arrays, parameter are fin length to height ratio, spacing
and orientation of geometry. In the longitudinally short fin array, where single chimney flow pattern is present hence heat
transfer coefficient is high. In long rectangular fin arrays, air is stagnant at central zone hence it is not so much contributed
in heat dissipation. In present study experimental setup is developed to studying the effect of natural convection over
rectangular fin array. Fin spacing, height and heater input are the parameter study during experimentation. Lampblack
coating is used to black fin surface. Flow patterns of various spacing’s are investigated using smoke flow visualization
techniques.
Keyword: Fin Arrays, Flow Visualization, Flow Pattern, Heat Transfer Coefficient, Natural convection.
Performance comparison of selection nanoparticles for insulation of three cor...IJECEIAES
This paper presents an investigation on the enhancement of electrical insulations of power cables materials using a new multi-nanoparticles technique. It has been studied the effect of adding specified types and concentrations of nanoparticles to polymeric materials such as PVC for controlling on electric and dielectric performance. Prediction of effective dielectric constant has been done for the new nanocomposites based on Interphase Power Law (IPL) model. The multi-nanoparticles technique has been succeeded for enhancing electric and dielectric performance of power cables insulation compared with adding individual nanoparticles. Finally, it has been investigated on electric field distribution in the new proposed modern insulations for three-phase core belted power cables. This research has focused on studying development of PVC nanocomposite materials performance with electric field distribution superior to the unfilled matrix, and has stressed particularly the effect of filler volume fraction on the electric field distribution.
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A Study on Stochastic Thermal Characterization of Electronic PackagesIJERA Editor
Insofar as the electronics can be found now in several applications of multiple domains, we have tried to
highlight in this study that, those systems must be based on unquestionable reliability and meet the needs of the
external environment. Starting from the unit "°c / w" concerning the thermal resistance from the gap between
junction temperature and a reference temperature, we have tried to compare the thermal performance of
electronic packages taking into consideration the thermal management. Our approach is based on the Monte
Carlo simulation and the stochastic characterization of the QFN. From the norm of normalization, we have
obtained standardized data sheets allowing accurate comparisons of the thermal performance of electronic
packages as produced by different manufacturers. Our numerical model through simulation, prototyping
concerning the design involves the JEDEC recommendations, which we consider a very interesting alternative.
Through the deterministic analysis, we conducted an analysis from the Matlab program parameters, which
control the Ansys software, the results were processed by statistical techniques to evaluate the times of the
thermal resistance of the QFN. That is why we must consider the electronic package (encapsulating the
integrated circuit), through the printed circuit board (PCB) to ensure the junction temperature maintenance and
avoid the dissipation of the heat. Also our process was based on the union of the finite element method to the
Monte Carlo simulation and stochastic characterization of the QFN.
Keywords: Electronic package; Finite element method; printed
This document describes thermal analysis of an electronic package using TAMS and TNETFA software tools. TAMS and TNETFA are FORTRAN codes that use lumped modeling to analyze heat transfer through multilayer structures like printed circuit boards. The document details the theoretical basis of the codes and provides an example analysis of a printed circuit board with 34 heat-generating components. The board is modeled with both 1-resistor and 2-resistor component models in TNETFA and results are compared to a commercial software, showing good agreement. The analysis provides insight into the thermal behavior of the electronic package and components under different operating conditions.
The effect of magnetic field direction on thermoelectric and thermomagnetic c...Muhammid Al-Baghdadi
This document investigates the effect of magnetic field direction on thermoelectric and thermomagnetic coefficients of undoped single crystalline InSb at room temperature. It describes how samples of InSb were tested under varying magnetic fields and temperature gradients to measure the Seebeck and Nernst coefficients. The results showed that the Seebeck coefficient depended only on the temperature gradient, while the Nernst coefficient depended on both the temperature gradient and magnetic field. However, the values of the thermoelectric and thermomagnetic coefficients were found to be independent of the direction of the applied magnetic field with respect to the InSb sample surface.
4.thermal stress analysis of peek fiber composites at cryogenic temperatureEditorJST
Fiber reinforced composites are class of materials that are workable engineering materials
possessing high strength to weight ratio resulting in reduction of weight and hence savings in energy.
Composites can be tailor -made to the required duty by changing the nature and proportion of the constituent
materials. Composites exhibit anisotropy in mechanical and thermal properties. This makes the design of
composite structures more complex and demanding. Composites have wide applications as supports and
structures at cryogenic temperatures in super conducting magnets and as fuel tankage in spacecraft and rocketry.
As these composites are fabricated at 1000 C to 2000 C, ~ their use at low temperatures creates thermal stresses.
They become brittle at low temperatures and thermal strain of matrix ma:f be of the same order of the ultimate
tensile strain at helium temperature (4.2K); thus leaving no more load bearing capability.
This document discusses microwave heating principles and their application to regenerating granular activated carbon. It begins by explaining that microwave heating uses electromagnetic waves to heat dielectric materials through dipolar interactions. It then discusses factors that influence heating uniformity such as material properties and equipment design. Specifically, it notes challenges in achieving uniform heating and describes common microwave equipment components like magnetrons, applicators, and control systems. The document concludes by examining how these principles apply to microwave regeneration of granular activated carbon used in the carbon-in-pulp paper processing, finding that microwaves can effectively regenerate used carbon.
This document summarizes a new method for temperature compensation of a circular cavity resonator using a low conductivity cooling water system based on convection heat transfer. The method measures the heat load and heat exchange to determine the optimal mass flow rate of cooling water to maintain temperature stability. By analyzing the temperature characteristics and developing a model of the compensated resonator, simulation results confirmed this approach can significantly reduce temperature drift of the resonant frequency compared to an uncompensated design.
1) The paper discusses insulation coordination challenges for Gas Insulated Switchgear (GIS) substations connected to overhead lines via underground cables. Short cable lengths complicate insulation practices due to fast front transients from lightning and switching.
2) A literature review found that GIS failure rates increase with voltage level, with 61% of failures from nominal voltage and 39% from overvoltage. Only one failure was reported due to lightning.
3) The paper reports on modeling work to examine factors like cable length, tower footing resistance, and surge arrester placement that influence transient overvoltages and the effectiveness of mitigation methods. Preliminary results suggest surge arresters and low tower footing resistance are effective at controlling overvoltages.
Ph d defense_rajmohan_muthaiah_University_of_oklahoma_07_28_2021Rajmohan Muthaiah
This slide describes the thermal transport in polymers, polymer nanocomposites and semiconductors using molecular dynamics simulations and first principles calculations
This document discusses using magnetic permeability to store information in a way that is insensitive to magnetic fields and temperature changes. It summarizes methods for creating regions of different permeability in two materials - Metglas films and permalloy/copper bilayers. For the bilayers, annealing or ohmic heating can convert high permeability permalloy to low permeability by causing copper diffusion. Metglas bits as small as 300 nm can be written by laser heating to change the material from amorphous to crystalline phase. Permeability bits in both materials were read using magnetic tunnel junction sensors and were found to withstand gamma radiation, suggesting suitability for long-term storage.
Undergrounding high voltage_electricity_transmission_lines_the_technical_issu...Ivan Rojas Soliz
Undergrounding high voltage electricity transmission lines has several technical challenges compared to overhead lines. Underground cables require robust insulation unlike overhead lines which use air insulation. They also generate more heat that must be dissipated through larger cable size or cooling systems. Installation methods for underground cables like direct burial or tunneling require extensive excavation and have higher capital costs than equivalent overhead lines. Maintenance and repairs of underground cables are also more complex and time consuming. While undergrounding reduces visual impacts, it has other environmental and planning considerations regarding land use restrictions and potential disturbances during installation and maintenance.
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2. 538 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 23, NO. 2, APRIL 2008
Fig. 1. Ampacity as a function of soil thermal resistivity [9]. Fig. 2. Procedure to compute T for nonhomogenous backfill arrangement.
installed in conduits or directly buried. When the cables are
touching, a difference is made depending on whether the cables
are laid in trefoil or flat formations. Different expressions are
used for equally and unequally loaded cables. A thorough de-
scription of the history and theory of ampacity calculations can
be found in [11].
In the Neher–McGrath method, a backfill is treated as an
equivalent cylindrical surface whose radius depends on the
width and height of the backfill.
B. Calculation of Using the Finite Element Method
When the medium surrounding the cables is composed of
several materials with different thermal resistivities, standard
methods cannot be applied. However, an approximate solution
can be found using the finite element method. The approach is
based on the observation that the temperature rise at the sur- Fig. 3. Complex cable installation suitable for the computation of T applying
face of the cable above ambient is equal to the finite element method proposed in this paper.
(1)
tant difference with respect to an approach using only the finite
where represents the total losses inside the cable. If we set element method for the computation of the thermal fields. In the
and , then latter case, much longer simulation times can be expected.
Fig. 3 shows a complex installation that can be solved with
(2) this method. In addition to the native soil, the installation
comprises several materials with different thermal resistivities,
where is the cable/duct surface temperature. namely: two soil layers, three sets of ducts in trefoil in a back-
The proposed approach requires building a finite element fill, several cables in trefoil installed in a duct bank and a steam
mesh and solving the resulting heat transfer equations for the pipe.
temperature at the cable surface. Fig. 2 shows an example The first natural question that arises in the approach proposed
including the details of the cable. In the majority of cases, the here is how it compares with the standard methods of calcu-
cable surface is not an isotherm; hence there is a question of lations for the cases where such comparisons can be made. This
which temperature to choose for (2). A conservative approach question is addressed in the remainder of this paper.
would be to use the highest value. An alternative would be to
use an average temperature. The latter approach is taken in the
III. VARYING SOIL THERMAL RESISTIVITY
developments that will be presented.
Adiabatic boundaries are set sufficiently far away on both Several backfilling arrangements are investigated with para-
sides and the bottom of the installation (boundaries not shown metric studies. The thermal resistivity of the native soil is varied
in Fig. 2). Experience has shown that these boundary conditions between 0.5 and 4.0 K.m/W. The two approaches described
result in a negligible error when computing cable temperature above for computing are compared in every case.
[14]. The soil surface can be represented as an isothermal or a
convective boundary. A. Base Case—Directly Buried Cables
Once is known, ampacity calculations can be efficiently The geometry of the base case is shown in Fig. 4. It con-
performed with the standardized procedures. This is an impor- sists of three trefoil arrangements. The cable construction de-
3. DE LEÓN AND ANDERS: EFFECTS OF BACKFILLING ON CABLE AMPACITY 539
Fig. 7. Three different quantities of backfill.
Fig. 4. Case base—directly buried trefoils.
Fig. 8. Ampacity for different quantities of backfill.
soil. Two cases are compared, when is computed as in the
Fig. 5. Construction details of the cable used for the simulations. standards and with the finite element method.
Three quantities of backfill were examined; see Fig. 7. One
(small) has dimensions of 0.7 0.5 m (area 0.35 m ), an-
other (medium) with dimensions of 1.2 1.0 m (area 1.2
m ), and the last (large) with dimensions of 2.0 1.5 m (area
3 m ). The thermal resistivity of the soil is varied between 0.5
and 4.0 K.m/W. Fig. 8 shows the ampacity for the arrangements
when using the finite element method. As expected, a greater
quantity of backfill with a greater area yields larger ampacity.
In these examples, the ampacity is increased by 37.5% for the
small backfill, 72% for the medium backfill, and by 95% for
the large one with respect to the directly buried case. Increasing
the backfill quantity incurs additional installation costs. There
is an optimal amount of backfill beyond which the increase in
the cable rating does not compensate the additional costs. This
Fig. 6. Ampacity for the case base—directly buried trefoils. topic is analyzed in [12].
Fig. 9 shows the differences in percent between the am-
pacities calculated with the two methods. The reference is the
tails are given in Fig. 5. Fig. 6 shows the variation of ampacity ampacity computed with the finite element method. For the
with thermal resistivity of the soil comparing the two methods directly buried case and the large backfill, the differences are
for computing . It can be seen that both methods give approxi- small (mostly less than 3%) and negative. Thus, the standard-
mately the same ampacity for the entire range of the soil thermal ized method computes ampacities slightly on the optimistic
resistivities. It is interesting to note that the ampacity for a soil side. However, for the small and medium backfills, the stan-
resistivity of 4.0 K.m/W is less than half of that for 0.5 K.m/W. dardized method gives ampacities mostly on the pessimistic
side with differences ranging from 2% to 11%.
B. Case with a Thermal Backfill C. Varying the Depth of the Backfill
The effects on ampacity of the cable arrangement in Fig. 4 Numerical experiments were performed to find the differ-
installed in a backfill with a low value of thermal resistivity are ences between the standard and the finite element methods as
analyzed as a function of the thermal resistivity of the native the depth of the backfill varies. The distance from the top of
4. 540 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 23, NO. 2, APRIL 2008
Fig. 12. Extreme cases for varying the width of the backfill.
Fig. 9. Difference in ampacities using standard and finite element methods for
the calculation of T for different backfill quantities.
Fig. 13. Ampacity versus backfill width.
shallowest case (0.1 m), the finite element results are somewhat
optimistic. Similar results were obtained for other combinations
of the thermal resistivities.1
Fig. 10. Varying the depth of the backfill from 0.1 m to 10 m.
IV. VARYING WIDTH AND HEIGHT
The standardized methods for the computation of cable am-
pacity for backfill installations are valid for the ratios of width
to height ranging from 1/3 to 3. In reference [4], extensions to
the standard methods were given. Here, we compare the stan-
dardized methods, including the extensions, against the finite
element results.
A. Varying Width
The width of the backfill was varied from 0.7 m to 4.0 m; the
thermal resistivities for the native soil and backfill are 1.0 and
0.5 K.m/W, respectively. Fig. 12 shows the arrangement for the
Fig. 11. Ampacity versus installation depth comparing the two methods for extreme cases and Fig. 13 displays the comparative results. The
computing T . width to height ratios were varied between 1.4 and 8.
From Fig. 13, we can observe that the standardized methods
compute the ampacity on the conservative side of around 4%
the backfill to the surface was varied from 0.1 m to 10 m; see (for this case). This fact was previously noticed in [4]. The
Fig. 10. The results are shown in Fig. 11 for thermal resistivi- authors showed that the geometric factor obtained with the
ties of 1.0 and 0.5 K.m/W for the native soil and the backfill, Neher–McGrath method decreases as the height to width ratio
respectively. As expected, the ampacity decreases as the depth 1The finite element approach has one more advantage over the standard
increases. Both methods give virtually the same results for every method for shallow buried cables. Namely, it allows performing analysis with
depth. The largest difference is under 2% and happens for the a nonisothermal earth surface. This feature was not explored in this study.
5. DE LEÓN AND ANDERS: EFFECTS OF BACKFILLING ON CABLE AMPACITY 541
Fig. 16. Cable backfill plus a controlled backfill on top.
Fig. 14. Extreme cases for varying the height of the backfill.
Fig. 17. Ampacity gains using a controlled backfill on top.
Fig. 15. Ampacity versus backfill height.
V. CONTROLLED BACKFILLS ON TOP
increases contradicting the results of their (finite element)
scheme. The reason is that in the standard approach, the surface After digging a trench for the installation of underground ca-
of the backfill is assumed to be an isothermal cylinder. For very bles, it is a common practice to place the native soil on top of the
large (or small) width/height ratios, this is not true, especially backfill. However, when the native soil has unfavorable thermal
when the cables are clustered together as in our example. The resistivity (high value or it is prone to drying out), a controlled
regions of the backfill close to the cables are hotter than the far backfill with a lower thermal resistivity than the soil can be used.
away regions. Fig. 16 depicts such a situation.
A parametric study has been performed to find the ampacity
gains for installations with a controlled (or engineered) backfill.
B. Varying Height The cables are installed in a small backfill centered at a depth
of 1 m with a thermal resistivity of 0.5 K.m/W. The thermal
The height of the backfill was varied from 0.5 to 4.0 m with a resistivities of both the soil and the controlled backfill have been
constant width of 0.7 m. This range covers width to height ratios varied between 0.5 and 4.0 K.m/W.
from 0.714 to 5.71. The initial position of the backfill is now 2 m Fig. 17 shows the variation in ampacity for several conditions:
(rather than 1 m) to give more room for the variations. Fig. 14 No controlled backfill on top, adding controlled backfill with
depicts the extreme situations and Fig. 15 shows the computed thermal resistivities of 0.5, 1.0, and 1.5 K.m/W. From Fig. 17
ampacities with the standardized methods, the extensions pub- one can appreciate that substituting the native soil with a ma-
lished in [4] and the finite element approach. terial of lower thermal resistivity can substantially increase the
We can observe that the standardized method (up to a ratio ampacity of the cables. As expected, greater ampacity benefits
of width to height of 3) computes the ampacity with less than are obtained when the thermal resistivity of the native soil is
2% difference with respect to the finite element approach. The higher. In our example, the improvement in ampacity is more
extensions give maximum differences of 9%. In both cases, the than 42% when we add a controlled backfill of 0.5 K.m/W sub-
differences are on the optimistic side (i.e., the computed am- stituting a soil with a thermal resistivity of 4.0 K.m/W.
pacity is larger than the reference ampacity computed with the All simulations in this section have been performed with the
finite element method). finite element method. The standardized procedures do not have
6. 542 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 23, NO. 2, APRIL 2008
against the method using the finite element approach are as
follows.
• The standard methods accurately match the results from
finite element when the cables are directly buried.
• The standardized methods tend to slightly underestimate
the ampacity when the cables are installed in a well-shaped
backfill (ratio width/height from 1/3 to 3) by a few per-
centage points. As the installation depth increases, the dif-
ferences between the two methods decrease.
• The extensions to the calculation of the geometric factors
proposed by El-Kady and Horrocks work relatively well
for backfills with ratios width to height larger than 3. How-
Fig. 18. Ampacity for three important cases: directly buried cables, cables in ever, for backfills with ratios width to height smaller than
backfill, and cables in backfill plus a controlled backfill on top.
1/3, the El-Kady/Horrocks approach overestimates the am-
pacity from 5 to 10%.
• In the standards, there is no procedure for computing in
expressions for computing for the geometrical arrangement
depicted in Fig. 16. cases where a controlled backfill is used on top of the main
backfill.
VI. SUMMARY OF RESULTS All of the simulations in this paper have been carried out with
the commercially available program for thermally rating cables,
Fig. 18 compares the three most important cases: the worst- CYMCAP, where the algorithms presented in this paper have
case scenario, when the cables are directly buried as in Fig. 4; been included [13].
the standard backfill case; and the best-case scenario, when the
cables are installed in a backfill and with a controlled backfill
on top (Fig. 16). The increase in ampacity when the cables are
REFERENCES
installed in a backfill varies between 0% and 37.5% with respect
to the directly buried case. When a controlled backfill is added, [1] IEEE Guide for Soil Thermal Resistivity Measurements, IEEE Std. 442,
the increase in ampacity varies from 0% to 95% of the ampacity 1981.
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rise and load capability of cable systems,” AIEE Trans. Part III—Power
App. Syst., vol. 76, pp. 752–772, Oct. 1957.
VII. CONCLUSION [3] Electric Cables—Calculation of the current rating—Part 2: Thermal
resistance—Section 1: Calculation of the thermal resistance, IEC Std.
A finite element method for the computation of the thermal 60287-2-1, 2001-11.
resistance external to the cable has been proposed. The [4] M. A. El-Kady and D. J. Horrocks, “Extended values of geometric
method represents an effective alternative to the use of a full factor of external thermal resistance of cables in duct banks,” IEEE
Trans. Power App. Syst., vol. PAS-104, no. 8, pp. 1958–1962, Aug.
thermal finite element program. Once is computed, the 1985.
proposed approach applies the standardized rating procedures. [5] M. A. El-Kady, G. J. Anders, D. J. Horrocks, and J. Motlis, “Modified
This combination of methods gives the possibility of efficiently values for geometric factor of external thermal resistance of cables in
rating cables installed in nonhomogenous soils and/or backfill ducts,” IEEE Trans. Power Del., vol. 3, no. 4, pp. 1303–1309, Oct.
1988.
arrangements. [6] E. Tarasiewicz, M. A. El-Kady, and G. J. Anders, “Generalized
A parametrical study on the effects of backfilling on cable am- coefficients of external thermal resistance for ampacity evaluation of
pacity has been presented. The analysis includes the comparison underground multiple cable systems,” IEEE Trans. Power Del., vol.
PWRD-2, no. 1, pp. 15–20, Jan. 1987.
of two methods for computing the external thermal resistance. [7] S. M. Sellers and W. Z. Black, “Refinements to the Neher-McGrath
The most important conclusions on the use of the backfills are model for calculating the ampacity of underground cables,” IEEE
as follows. Trans. Power Del., vol. 11, no. 1, pp. 12–30, Jan. 1996.
[8] CIGRE, “The calculation of the effective thermal resistance of cables
• Backfilling is an effective (technically speaking) way to
laid in materials having different thermal resistivities,” Electra, No. 98,
increase ampacity. Installing a small quantity of backfill 1985, pp. 19–42.
can produce sizable ampacity gains. [9] F. de Leon, “Major factors affecting cable ampacity,” presented at the
• The improvements in ampacity of backfilling are more sig- IEEE/Power Eng. Soc. General Meeting, Montreal, QC, Canada, Jun.
18–22, 2006, paper 06GM0041.
nificant when the thermal resistivity of the native soil is [10] IEEE Standard Power Cable Ampacity Tables, IEEE Std. 835-1994.
high. [11] G. J. Anders, Rating of Electric Power Cables: Ampacity Computations
• The quantity of the backfill substantially affects the for Transmission, Distribution, and Industrial Applications. Piscat-
away, NJ: IEEE Press, 1997.
ampacity. [12] G. J. Anders, Rating of Electric Power Cables in Unfavorable Thermal
• Controlled backfills on top of already backfilled cables can Environment. Piscataway, NJ: IEEE Press, 2005.
significantly increase the ampacity when the native soil has [13] CYMCAP for Windows, CYME Int. T&D, Nov. 2006. St. Bruno,
high thermal resistivity. QC, Canada.
[14] D. Mushamalirwa, N. Germay, and J. C. Steffens, “A 2-D finite ele-
The most important conclusions on the comparison of the ment mesh generator for thermal analysis of underground power ca-
standardized methods for the computation of the value of , bles,” IEEE Trans. Power Del., vol. 3, no. 1, pp. 62–68, Jan. 1988.
7. DE LEÓN AND ANDERS: EFFECTS OF BACKFILLING ON CABLE AMPACITY 543
Francisco de León (S’86–M’92–SM’02) was born George J. Anders (M’74–SM’84–F’99) received the
in Mexico City, Mexico, in 1959. He received the M.Sc. degree in electrical engineering from the Tech-
B.Sc. and the M.Sc. (Hons.) degrees in electrical nical University of £odz, £odz, Poland, in 1973, and
engineering from the National Polytechnic Insti- the M.Sc. degree in mathematics and the Ph.D. de-
tute, Mexico, in 1983 and 1986, respectively, and gree in power system reliability from the University
the Ph.D. degree from the University of Toronto, of Toronto, Toronto, ON, Canada, in 1977 and 1980,
Toronto, ON, Canada, in 1992. respectively.
He has held several academic positions in Mexico Since 1975, he has been with Ontario Hydro, first
and has worked for the Canadian electric industry. as a System Design Engineer in the Transmission
From 2004 to 2007, he was the Director of R&D of System Design Department of the System Planning
CYME International T&D, St. Bruno, QC, Canada. Division, and currently as a Principal Engineer
Currently, he is an Associate Professor in the Department of Electrical and Com- with Kinectrics, Inc. (a successor company to Ontario Hydro Technologies),
puter Engineering at the Polytechnic University, Brooklyn, NY. His research in- Toronto, ON, Canada, and an Adjunct Professor in the Department of Electrical
terests include the analysis of power systems, the electromagnetic and thermal and Computer Engineering of the University of Toronto and the Technical
design of machines and cables, and the definitions of power under unbalanced University of Lodz. He has written several books, including Rating of Electric
and nonlinear conditions. Power Cables: Ampacity Computation for Transmission, Distribution, and
Industrial Applications (IEEE Press, 1997, and McGraw-Hill, 1998) and Rating
of Electric Power Cables in Unfavorable Thermal Environment (IEEE Press,
2005).
Dr. Anders is a Registered Professional Engineer in the Province of Ontario,
Canada.