Power Cable Ratings and Soil Considerations
Presented jointly by:
Power Delivery Consultants, Inc.
Geotherm, Inc.
Anders Consulting, Ltd.
Ampacity Is Important ! Underground cables generally have lower ratings than the utility's overhead lines - and the dollars per ampere are much higher. Over-designing is costly and under-designing is very costly. It is therefore desirable to confidently rate the cables near their ultimate limit.
Important issues include:
OVERVIEW
Cable ampacity analysis has assumed new importance in the last several years, as first-time users need to evaluate underground cable alternatives, as guided boring has become a common installation method, as the use of submarine cables increases, and as wind farms and data centers are growing in numbers.
MATERIAL
The course will focus on discussing various topics regarding ampacity and the effects of soil - the most significant variable and often the least understood - on ampacity, installation design, and operation. While PC-based ampacity programs exist, a good understanding of the ampacity techniques (e.g., Neher-McGrath, IEC 60287/60853) is extremely important. Trench optimization is becoming more common as utilities attempt to obtain the most amperes from a cable. More attention is being paid to proper modeling of daily, weekly, and even monthly load shapes to take into account "cool-down" periods during load cycling, which permit higher loading during peak periods. The earth gives the largest single thermal resistance and thermal capacitance, and it also has by far the greatest variability with distance along the route, and even with time. Earth thermal resistance can easily vary threefold on a specific circuit, and the cable must be rated for the worst-case condition. Recent improvements in thermal measurement instruments and techniques, coupled with a better understanding of soil mechanics and innovations in controlled backfill such as Fluidized Thermal Backfill permit much better representation and control of the earth thermal circuit, with the resulting ampacity increases.
EXPECTED LEARNING OUTCOMES/OBJECTIVES
PDC has identified learning objectives we expect each student to obtain on completion of this course. The student completing this course should be able to:
PREREQUISITES
Participants: This course is intended for engineers and field personnel concerned with planning cable systems, calculating ampacity, performing soil thermal analysis, and insuring field quality control. Experience in ampacity calculations is not necessary, but it is assumed the participant has a solid understanding of underground cable systems. Participant may want to consider taking PDC’s Extruded Dielectric or Pipe-Type Cable course prior to taking this Ampacity course. Much of the course content is devoted to understanding the steps in performing an ampacity calculation, developing a thorough understanding of the earth thermal resistance, capacitance, and stability, and understanding the impact of non-standard (but common) cable installations. Theoretical analysis and practical applications are provided.
COURSE TOPICS
INSTRUCTORS FOR THE COURSE MAY INCLUDE
Jay Williams, P.E., Executive Engineer, Power Delivery Consultants, Inc. Mr. Williams has been conducting ampacity analyses for more than 40 years. He developed the original EPRI ACE program for ampacity calculations for underground cable systems, and conducts several ampacity studies for utilities and others each year.
Rachel Mosier, P.E., Principal Engineer, Power Delivery Consultants, Inc. Ms. Mosier has been conducting ampacity analyses for more than 20 years, as a cable engineer working for a large utility as well as for other utilities around the country, often for non-standard installations. She is a member of CIGRE, and an active member of the IEEE PES Insulated Conductors Committee (ICC).
Deepak Parmar, President, Geotherm, Inc. Mr. Parmar has specialized in soil thermal analysis and soil mechanics for more than 25 years. He has performed soil thermal analyses throughout the world, and has taught several dozen seminars on soil thermal analysis. He performs field surveys and laboratory analyses, and provides soil thermal test equipment. He is a member of CIGRE, and an active member of the IEEE PES ICC.
Dr. George Anders, President of Anders Consulting, Ltd, is an expert in analyzing highly unusual cable installations with over 40 years of industry experience. He is a professor at the University of Toronto and the Technical University of Lodz, as well as a retired principal scientist from Kinectrics. He is a member of IEC, and an active member of the IEEE PES ICC. He is the author of 10 books, including Probability Concepts in Electric Power Systems, Rating of Electric Power Cables in Unfavorable Thermal Environment, and Rating of Electric Power Cables.
CONTINUING EDUCATION UNITS
Upon request, PDC will issue students a course certificate indicating the number of Continuing Education Units for the course completed based on national guidelines and the number of classroom hours. 2.8 Continuing Education Units (CEUs) will be awarded for successful completion of this course. One CEU is equal to ten classroom hours.
TUITION AND ENROLLMENT
The tuition cost includes enrollment, a comprehensive set of course notes, breakfast, lunch, and coffee breaks, as well as a class dinner on the first night.
Presented jointly by:
Power Delivery Consultants, Inc.
Geotherm, Inc.
Anders Consulting, Ltd.
Ampacity Is Important ! Underground cables generally have lower ratings than the utility's overhead lines - and the dollars per ampere are much higher. Over-designing is costly and under-designing is very costly. It is therefore desirable to confidently rate the cables near their ultimate limit.
Important issues include:
- Reducing cost now and uprating the circuit in the future
- Short-term and longer-term operation above standard temperature levels
- Extruded-dielectric cables in steel pipe and in casings
- Ampacity audits and uprating for existing cables
- Soil thermal stability - is it really an issue?
- Shield/sheath bonding on extruded-dielectric cables
- Fluidized thermal backfill versus compacted fills
- Temperature monitoring; dynamic rating approaches
- What are your options for monitoring cables and using results effectively?
OVERVIEW
Cable ampacity analysis has assumed new importance in the last several years, as first-time users need to evaluate underground cable alternatives, as guided boring has become a common installation method, as the use of submarine cables increases, and as wind farms and data centers are growing in numbers.
MATERIAL
The course will focus on discussing various topics regarding ampacity and the effects of soil - the most significant variable and often the least understood - on ampacity, installation design, and operation. While PC-based ampacity programs exist, a good understanding of the ampacity techniques (e.g., Neher-McGrath, IEC 60287/60853) is extremely important. Trench optimization is becoming more common as utilities attempt to obtain the most amperes from a cable. More attention is being paid to proper modeling of daily, weekly, and even monthly load shapes to take into account "cool-down" periods during load cycling, which permit higher loading during peak periods. The earth gives the largest single thermal resistance and thermal capacitance, and it also has by far the greatest variability with distance along the route, and even with time. Earth thermal resistance can easily vary threefold on a specific circuit, and the cable must be rated for the worst-case condition. Recent improvements in thermal measurement instruments and techniques, coupled with a better understanding of soil mechanics and innovations in controlled backfill such as Fluidized Thermal Backfill permit much better representation and control of the earth thermal circuit, with the resulting ampacity increases.
EXPECTED LEARNING OUTCOMES/OBJECTIVES
PDC has identified learning objectives we expect each student to obtain on completion of this course. The student completing this course should be able to:
- Perform a basic ampacity (cable rating) calculation using a hand calculator.
- Understand the importance of soils and list the thermal characteristics that should be considered for cable ratings.
- Describe the impact of dielectric losses, system voltage and insulation material on ampacity.
- Understand some of the non-standard cable installations, how they must be considered, and the approach to solve for the impacts on ampacity.
PREREQUISITES
Participants: This course is intended for engineers and field personnel concerned with planning cable systems, calculating ampacity, performing soil thermal analysis, and insuring field quality control. Experience in ampacity calculations is not necessary, but it is assumed the participant has a solid understanding of underground cable systems. Participant may want to consider taking PDC’s Extruded Dielectric or Pipe-Type Cable course prior to taking this Ampacity course. Much of the course content is devoted to understanding the steps in performing an ampacity calculation, developing a thorough understanding of the earth thermal resistance, capacitance, and stability, and understanding the impact of non-standard (but common) cable installations. Theoretical analysis and practical applications are provided.
COURSE TOPICS
- Underground cable fundamentals
- Ampacity principles
- Temperature
- Dielectric & current-dependent losses
- Thermal resistance
- Ampacity formula
- Effects of design and installation variables
- Mutual heating
- Design variables
- Installation variables
- Thermal environment of underground power cables
- Heat flow and heat transfer through soil
- Factors affecting soil thermal properties
- Thermal stability
- Elements of a route thermal survey
- Corrective thermal backfills, FTB
- Weather induced effects
- Ducts, guided bores, submarine cable
- Hot spot remedial measures
- Wind/solar farms, data centers
- Soil thermal properties - videos, photos
- Installations with multiple soil layers
- Calculating allowable current step-by-step
- Ampacity example
- Transient and emergency ampacities
- Tabulations and computer programs
- Uprating, Dynamic Rating, Distributed Temperature Monitoring
- Distribution cable ampacities
- Effects of unfavorable thermal environment on ampacity
- Cable crossings
- Cables in unventilated and ventilated tunnels
- Deeply buried cables, equivalent depth
- AC resistance of large segmental conductors - new findings
- Submarine Cables
- Examples of difficult, non-standard installations
- Cables in steel casings
- Thermal resistance of air gap for cables in a conduit
- Horizontal vs Inclined Ducts
- Cables on riser poles
- Bundled cables
INSTRUCTORS FOR THE COURSE MAY INCLUDE
Jay Williams, P.E., Executive Engineer, Power Delivery Consultants, Inc. Mr. Williams has been conducting ampacity analyses for more than 40 years. He developed the original EPRI ACE program for ampacity calculations for underground cable systems, and conducts several ampacity studies for utilities and others each year.
Rachel Mosier, P.E., Principal Engineer, Power Delivery Consultants, Inc. Ms. Mosier has been conducting ampacity analyses for more than 20 years, as a cable engineer working for a large utility as well as for other utilities around the country, often for non-standard installations. She is a member of CIGRE, and an active member of the IEEE PES Insulated Conductors Committee (ICC).
Deepak Parmar, President, Geotherm, Inc. Mr. Parmar has specialized in soil thermal analysis and soil mechanics for more than 25 years. He has performed soil thermal analyses throughout the world, and has taught several dozen seminars on soil thermal analysis. He performs field surveys and laboratory analyses, and provides soil thermal test equipment. He is a member of CIGRE, and an active member of the IEEE PES ICC.
Dr. George Anders, President of Anders Consulting, Ltd, is an expert in analyzing highly unusual cable installations with over 40 years of industry experience. He is a professor at the University of Toronto and the Technical University of Lodz, as well as a retired principal scientist from Kinectrics. He is a member of IEC, and an active member of the IEEE PES ICC. He is the author of 10 books, including Probability Concepts in Electric Power Systems, Rating of Electric Power Cables in Unfavorable Thermal Environment, and Rating of Electric Power Cables.
CONTINUING EDUCATION UNITS
Upon request, PDC will issue students a course certificate indicating the number of Continuing Education Units for the course completed based on national guidelines and the number of classroom hours. 2.8 Continuing Education Units (CEUs) will be awarded for successful completion of this course. One CEU is equal to ten classroom hours.
TUITION AND ENROLLMENT
The tuition cost includes enrollment, a comprehensive set of course notes, breakfast, lunch, and coffee breaks, as well as a class dinner on the first night.