A History of Medium & High Voltage Cables - Georgia Tech & NEETRAC
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A History of Medium & High Voltage Cables - Georgia Tech & NEETRAC
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A History of Medium & High Voltage Cables - Georgia Tech & NEETRAC
- 1. History of Cable Systems HISTORICAL OVERVIEW OF MEDIUM & HIGH VOLTAGE CABLES Nigel Hampton Copyright GTRC 2012
- 2. History of Cable Systems Objective 2 “To present the evolution of cables in time to understand the lessons from the past: the legacy problems and their solution” Outline • Timeline • Cable components • Legacy problems - Cables • Current challenges
- 3. History of Cable Systems Timeline 3
- 4. History of Cable Systems Cable History 4 Historical perspective is important, it tells us: • What works • What does not • What is still out there • What challenges it presents • How large the problems may be or become • How to avoid mistakes
- 5. History of Cable Systems Timeline 1812-1942 5 1812: First cables used to detonate ores in a mine in Russia 1942: First use of Polyethylene (PE) in cables 1917: First screened cables 1870: Cables insulated with natural rubber 1880: DC cables insulated with jute in “Street Pipes” – Thomas Edison 1890: Ferranti develops the concentric construction for cables 1925: The first pressurized paper cables 1937: Polyethylene (PE) developed
- 6. History of Cable Systems Timeline 1963-1990 6 1963: Invention of crosslinked polyethylene – XLPE 1990: Widespread use of WTR materials - Be, Ca, De, Ch & US 1982: WTR materials for MV in USA & Germany 1967: HMWPE insulation on UG cables in the US (Unjacketed tape shields) 1968: First use of XLPE cables for MV (mostly unjacketed, tape shields) 1972: Problems associated with water trees (MV) and contaminants (HV) Introduction of extruded semicon screens 1978: Widespread use of polymeric jackets in US & Ca 1989: Supersmooth conductor shields for MV cable in North America
- 7. History of Cable Systems Insulation History - Global 7 Year Voltage(kV) 20001975195019251900 600 500 400 300 200 100 0 Paper Polymer Type Ref [11]
- 8. History of Cable Systems AEIC Standards Development - MV 8 MV Cables 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1900 1920 1940 1960 1980 2000 2020 Year EditionNumber Laminated Insulation Extruded Insulation Laminated Insulation: AEIC CS1 Extruded Insulation: AEIC CS8 (previous CS5 and CS6)
- 9. History of Cable Systems AEIC Standards Development – HV / EHV 9 Laminated Insulation: AEIC CS4 (Low- Medium Pressure) AEIC CS2 (High Pressure) Extruded Insulation: AEIC CS7, CS9 and CG40 1 2 3 4 5 6 7 8 9 1920 1940 1960 1980 2000 2020 EditionNumber Year HV-EHV Cables Laminated Insulation Low-Medium Pressure Laminated Insulation High Pressure Extruded Insulation
- 10. History of Cable Systems Initial American Installations 10 Ref [7]
- 11. History of Cable Systems From Edison’s to Today’s Cable 11 Edison “Street Pipe” Picture: Brian Besconnal Pictures: PrysmianPicture: Southwire Picture: Black, 1983
- 12. History of Cable Systems Cable Components 12 6. Jacket (Recommended) 5. Metallic Shield 4. Insulation Shield or Screen 3. Insulation 2. Conductor Shield or Screen 1. Conductor Picture: Southwire
- 13. History of Cable Systems 1. Conductor 13 “Carries the current” • Resistance should be small to reduce power losses: • Flexibility, weight and susceptibility to corrosion are concerns together with economical issues such as cost, availability, and salvage value P = R x I2
- 14. History of Cable Systems Conductor Characteristics 14 Conductor Aluminum Stranded Solid Copper Stranded Blocked Unblocked Blocked Unblocked
- 15. History of Cable Systems 2. Conductor Shield 15 With no conductor shield, electric field lines are concentrated, creating high stress points at the conductor/insulation interface. “Provides for a smooth interface between the conductor and the insulation” Finite Element Simulation High Stress
- 16. History of Cable Systems Conductor Shield Characteristics 16 Conductor Shield Bonded Conventional Supersmooth Superclean (SS/SC) Conductor shields are semiconductive, so they are neither an insulator nor a conductor. Semiconducting materials are based on carbon black (manufactured by controlled combustion of hydrocarbons) that is dispersed within a polymer matrix On larger conductor sizes, tape shields are often used to prevent material “fall-in” between the strands during manufacture
- 17. History of Cable Systems 3. Insulation 17 “Contains voltage between the conductor and ground” • Must be clean • Must have smooth interfaces with the conductor and insulation shields • Must be able to operate at the desired: – Electrical Stress – Temperatures
- 18. History of Cable Systems Insulation - MV 18 Insulation Laminated Extruded PILC Thermoplastic Thermoset HMWPE XLPE WTR XLPE EPR Prior Technologies Today’s Technologies
- 19. History of Cable Systems MV Cable “Installed Capacity” In USA 19 Oldest Youngest Ref [18]
- 20. History of Cable Systems MV Extruded Cable Installed in USA 20 Year MVcablesinstalledintheUS(Millionsofft) 2000199419881982197619701964 7000 6000 5000 4000 3000 2000 1000 0 EPR TR XLPE XLPE HMWPE Data courtesy of Glen Bertini Ref [18]
- 21. History of Cable Systems Insulation – HV / EHV 21 Insulation Laminated Extruded Self Contained Thermoset XLPE EPR – HV only Pipe Type PPL - EHV only Paper Prior Technologies Today’s Technologies
- 22. History of Cable Systems Examples of Laminar Insulation Cables 22 Picture: Southwire Pictures: Prysmian
- 23. History of Cable Systems Examples of Extruded Insulation Cables 23 Pictures: Southwire Pictures: Prysmian
- 24. History of Cable Systems 4. Insulation Shield 24 “Keeps the voltage and stress within the insulation” With no insulation shield, electric field lines are concentrated, creating high stress points on the outside surface of the insulation. Finite Element Simulation High Stress
- 25. History of Cable Systems Belted Cables 25 • Early laminated cables had a “belt” of insulation over the core insulation. • This led to tangential stresses that were a cause of a lot of early failures Finite Element Simulation
- 26. History of Cable Systems Conductor and Insulation Shield (CS & IS) Effect 26 When both shields are: • smooth • intact Then, electric field lines are uniform, with a controlled electrical stress distribution. Finite Element Simulation
- 27. History of Cable Systems Insulation Shield – MV, HV, and EHV 27 Laminated Insulation Carbon Black Paper Perforated metallized paper Preferred in North America, Asia & parts of Europe. Thought to permit easier termination & splicing of cables but service performance is very dependent upon the workmanship / training of the installer, which is often variable Often same compound as CS
- 28. History of Cable Systems Types of Metallic Shields 28 Metallic Shield Tape Copper Aluminum Copper Laminated Sheath Stainless Steel Aluminum Copper Lead Corrugated Sheath Concentric Copper Wire Wire Flat Strap Extruded Aluminum Aluminum
- 29. History of Cable Systems Examples of Metallic Shields 29 Courtesy of Southwire A B C D E A – Welded Copper Corrugated Sheath B – Welded Aluminum Corrugated Sheath C – Concentric Copper Neutrals D – Copper Neutrals with Copper Composite Laminate Sheath E – Copper Neutrals with Aluminum Composite Laminate Sheath Pictures: Southwire
- 30. History of Cable Systems Types of Jackets Materials 30 Jacket Semiconductive Special Carbon black filled co polymers Neoprene Nylon Polypropylene LSF Hypalon* Standard PE PPPVC LLDPE MDPE HDPE * No longer available Enhanced Grounding Chemical / Thermal Resistance
- 31. History of Cable Systems Legacy Issues Cables 31
- 32. History of Cable Systems PILC Cables 32 • Differing designs – Belted vs. shielded – Jacketed vs. unjacketed • Lead corrosion (PILC) • Temperature performance and stability of impregnants • Draining of compounds – Dry insulations – Collapsed Joints • Overheating due to high dielectric losses • Moisture ingress leading to overheating • Loss of impregnant due to lead sheath leaks • Combinations of the above
- 33. History of Cable Systems Remaining PILC in US Networks 33 Where PILC remains on the system it retains a significant presence Estimated for US Utilities in 2010 (some utilities segregated) Ref [15]
- 34. History of Cable Systems The PILC experience teaches us that today’s decisions will be with engineers for a very long time 34 Ref [15]
- 35. History of Cable Systems Extruded Cables 35 • Differing designs – Jacketed vs unjacketed – Extruded shields vs graphite shields • Dirty insulation compounds (PE, early XLPE) • Insulations that were susceptible to water treeing (PE , early XLPE) • Poor manufacturing processes – Open compound handling procedures – Changing Formulations (EPR) • Inadequate cable designs – Unblocked conductors – Unjacketed cables – Cables with inadequate neutral designs • Combinations of the above
- 36. History of Cable Systems Current Challenges 36
- 37. History of Cable Systems 37 Percentages of failures of each component Termination 1.4% Joints 55.4% Cable 43.2% Accessories: Joints or splices, and Terminations Percentage of Failures per each Component Ref [17]
- 38. History of Cable Systems 38 Failure Modes Overheat 4% Dielectric breakdown 10% Aging 6% Corrosion 4% Moisture 4% Event 3% Manufacturing problem 14% Overload 2% Maintenance failure 2% Mechanical Damage 1% Contamination 1% Poor workmanship 49% Ref [17]
- 39. History of Cable Systems Building a Reliable Cable System 39 Customer Service Application Design Specs Materials Manu- facturing Testing Installation Operation Awareness