Cable History Doble Final Website

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History of Cable Systems

HISTORICAL OVERVIEW OF

MEDIUM & HIGH VOLTAGE CABLES

Nigel Hampton

Copyright GTRC 2012


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Objective

2

To present the evolution of cables in time to understandthe lessons from the past: the legacy problems and theirsolution

Outline Timeline

Cable components

Legacy problems - Cables

Current challenges


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Timeline

3


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Cable History

4

Historical perspective isimportant, it tells us:

What works What does not

What is still out there

What challenges it presents

How large the problems may beor become

How to avoid mistakes


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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 forcables

1925: The first pressurized paper cables

1937: Polyethylene (PE) developed


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Timeline 1963-1990

6

1963: Invention of crosslinked polyethylene XLPE

1990: Widespread use of WTRmaterials - Be, Ca, De, Ch & US

1982: WTR materials for MV in USA & Germany

1967: HMWPE insulation on UG cables in the US (Unjacketedtape shields)

1968: First use of XLPE cables for MV (mostly unjacketed,tape shields)

1972: Problems associated with water trees (MV) andcontaminants (HV)

Introduction of extruded semicon screens

1978: Widespread use of polymeric jackets in US & Ca

1989: Supersmooth conductor shields for MVcable in North America


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Insulation History - Global

7

Year

Voltage(kV)

20001975195019251900

600

500

400

300

200

100

0

Paper

Polymer

Type

Ref [11]


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AEIC Standards Development - MV

8

MV Cables

0

1

2

3

4

5

6

78

9

10

11

12

13

14

1900 1920 1940 1960 1980 2000 2020

Year

EditionNu

mber

Laminated Insulation Extruded Insulation

Laminated Insulation:

AEIC CS1

Extruded Insulation:

AEIC CS8 (previous

CS5 and CS6)


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AEIC Standards Development HV / EHV

9

Laminated Insulation:

AEIC CS4 (Low-

Medium Pressure)

AEIC CS2 (High

Pressure)

Extruded Insulation:

AEIC CS7, CS9 and

CG401

2

3

4

5

6

7

8

9

1920 1940 1960 1980 2000 2020

EditionN

umber

Year

HV-EHV Cables

Laminated Insulation Low-Medium Pressure

Laminated Insulation High Pressure

Extruded Insulation


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Initial American Installations

10

Ref [7]


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From Edisons to Todays Cable

11

Edison Street Pipe

Picture: Brian Besconnal

Pictures: PrysmianPicture: Southwire

Picture: Black, 1983


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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


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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


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Conductor Characteristics

14

Conductor

Aluminum

Stranded Solid

Copper

Stranded

Blocked

Unblocked

Blocked

Unblocked


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2. Conductor Shield

15

With no conductor shield,

electric field lines areconcentrated, creating high

stress points at the

conductor/insulation interface.

Provides for a smooth interface between the conductor andthe insulation

Finite

Element

Simulation

High

Stress


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Conductor Shield Characteristics

16

Conductor Shield

Bonded

ConventionalSupersmooth

Superclean (SS/SC)

Conductor shields are semiconductive, so they are neither an insulatornor 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


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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


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Insulation - MV

18

Insulation

Laminated Extruded

PILC Thermoplastic Thermoset

HMWPE XLPE

WTR XLPE

EPR

Prior Technologies

Todays Technologies


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MV Cable Installed Capacity In USA

19

Oldest Youngest

Ref [18]


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MV Extruded Cable Installed in USA

20

Year

MV

cablesinstalledintheUS(Millionsofft)

2000199419881982197619701964

7000

6000

5000

4000

3000

2000

1000

0

EPR

TR XLPE

XLPE

HMWPE

Data courtesy of Glen Bertini

Ref [18]


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Insulation HV / EHV

21

Insulation

Laminated Extruded

Self

Contained

Thermoset

XLPE

EPR HV only

Pipe Type

PPL- EHV only

Paper

Prior Technologies

Todays Technologies

Hi t f C bl S t


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Examples of Laminar Insulation Cables

22

Picture: Southwire

Pictures: Prysmian

Hi t f C bl S t


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Examples of Extruded Insulation Cables

23

Pictures: Southwire

Pictures:

Prysmian

Hi t f C bl S t


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4. Insulation Shield

24

Keeps the voltage and stress within the insulation

With no insulation shield,

electric field lines are

concentrated, creatinghigh stress points on the

outside surface of the

insulation.Finite

ElementSimulation

High

Stress

Hi t f C bl S t


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Belted Cables

25

Early laminated cables had a belt of insulation over thecore insulation.

This led to

tangentialstresses that

were a cause of

a lot of early

failuresFinite

Element

Simulation



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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



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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



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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



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Examples of Metall ic 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



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Types of Jackets Materials

30

Jacket

SemiconductiveSpecial

Carbon black filled

co polymers Neoprene

Nylon

Polypropylene

LSFHypalon*

Standard

PE PPPVC

LLDPE

MDPE

HDPE

* No longer available

Enhanced Grounding Chemical / Thermal Resistance



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Legacy Issues

Cables

31



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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



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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]



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The PILC experience teaches us that todays decisions

wil l be with engineers for a very long t ime

34

Ref [15]



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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



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Current Challenges

36



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y y

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]



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y y

38

Failure Modes

Overheat

4%

Dielectric

breakdown

10%

Aging

6%

Corrosion

4%

Moisture

4%

Event

3%

Manufacturing

problem

14%

Overload2%

Maintenance failure

2%Mechanical Damage

1%Contamination

1%

Poor

workmanship49%

Ref [17]



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y y

Building a Reliable Cable System

Customer

Service

Appl ication

Design Specs

Materials Manu-

facturing

Testing

Installation

Operation

Awareness

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