The document is a seminar report submitted by Mukesh Solanki to fulfill the requirements for a bachelor's degree in electrical engineering. The report discusses various types of power cables used for transmission and distribution of electricity, including overhead conductors such as AAC, AAAC, ACSR, ACAR, and underground cables. It provides details on the composition, properties, specifications and applications of different conductor types. The report aims to help understand the characteristics and selection criteria for optimal conductors based on transmission line design requirements.

1. A
SEMINAR REPORT
ON
“POWER CABLES”
Submittedinthepartialfulfilmentfor
bacheloroftechnology degreeat
RajasthanTechnicalUniversity,Kota
(2015-16)
Submitted To: - Submitted By:-
Ass. Prof. ANSHUL BHATI MUKESH SOLANKI
B.TECHIV YEAR

2. 1POWER CABLES
Department of Electrical & Electronics Engineering
VYAS INSTITUTE OF ENGINEERING AND TECHNOLOGY,
JODHPUR (Raj.)
VYAS INSTITUTE OF ENGINEERING &
TECHNOLOGY, JODHPUR (RAJ.)
DEPARTMENT OF ELECTRICAL& ELECTRONICS ENGINEERING
(2015-2016)
This is to certify that the student
MUKESH SOLANKI
of final year, have successfully completed the seminar on
“POWER CABLES”
towards the partial fulfilment of the degree of Bachelor’s of Technology
(B.TECH) In the Electrical & Electronics Engineering of the Rajasthan
Technical University during academic year 2015-2016.
Guided By:

3. 2POWER CABLES
Anshul Bhati Manish Bhati
Ass. Prof. (HOD, EEE)
CONTENT
 INTRODUCTION…………………………………………….3
 CONDUCTORS……………………………………………….4
 CONDUCTORS USED IN OH T/M LINE…….……………4
 CATEGORIES OF OVERHEAD CONDUCTOR………….5
 AAC……………………………………………………………6
 AAAC…………………………………………………………..6
 ACAR..…………………………………………………………7
 AACSR…………………………………………………………8
 ACSS…………………………………………………………...9
 ACCC…………………………………………………………10
 ACSR…………………………………………………………11
 SMOOTH BODY CONDUCTORS………………………...15
 VIBRATION RESISTANT CONDUCTOR……………….17
 SELF DAMPING CONDUCTOR…………………………..18
 BUNDLED CONDUCTOR………………………………….19
 SURFACE FINISHES……………………………………….20
 CHOICE OF OVERHEAD CONDUCTOR……………….21
 UNDERGROUND CABLE………………………………….21
 CONSTRUCTION OF UG CABLES…………………...….22

4. 3POWER CABLES
 INSULATING PROPERTIES FOR CABLES…………….23
 CLASSIFICATION OF CABLES………………………….23
 CONCLUSION………………………………………………25
 REFERENCES………………………………………………26
INTRODUCTION
Remarkable changes have occurred in the utility industry since Thomas Edison began the commercial
sale of electricity more than 100 years ago. One area that has undergone extensive change has been
in the types of conductors available to transmit and distribute electricity. Copper was the first metal
used to transmit electricity during the development of the electrical industry in the early 1880's. A
review of the selection criteria for transmission and distribution conductors, prior to the extensive use
of aluminum, suggests copper conductor sizes were being determined primarily on the basis of
mechanical considerations because of the disproportional high conductivity of copper relative to its
strength-to-weight ratio. Conductors were, therefore, generally larger than required from the
standpoint of efficient electrical conductivity. Because of the weight, span lengths were short, thus
increasing the overall cost of the transmission line.
Shortly before the turn of the century, aluminum began to replace copper as the metal of choice for
transmission and distribution conductors. The first transmission line using aluminum conductors was
constructed in California in 1895, quickly followed by a second line in 1898. The first transmission line
using a stranded (7-strand) aluminum cable was constructed by the Connecticut Electric Light
Company in 1899 and remained in daily operation for more than 50 years. Starting with these early
installations, the use of aluminum electrical conductors has increased steadily until it is the material of
choice by transmission line design engineers today. For more than 90 years aluminum has been used
by electric utilities for the transmission and distribution of electrical power. Although its almost
completely replacing copper for overhead applications. Of all the known non precious metals,
aluminum ranks second only to copper in volume conductivity. Aluminum possesses a conductivity -to-
weight ratio twice that of copper and its strength-to-weight ratio is 30% greater than copper.
When aluminum conductor came into relatively wide use in the early 1900's, experience indicated the
need for a conductor with a greater strength-to-weight ratio. Thus, in 1907 a new aluminum-steel
composite cable was introduced. This new conductor combined the light weight and high current
carrying capacity of aluminum with the high strength of a galvanized steel core. ACSR, as this
aluminum conductor, steel reinforced, cable became known, gained rapid acceptance and was used
almost exclusively throughout the world until 1939. The excellent conductivity of ACSR, coupled with
its excellent strength-to-weight ratio and ease of handling made it the dominant conductor for rural
electrification in the United States that began during the early 1920's.
In 1939 a new all aluminum-magnesium-silicon alloy cable was introduced. The new all-aluminum
alloy cable (AAAC) was developed to retain the mechanical and electrical properties of ACSR while
improving weight and corrosion resistance characteristics. The introduction of the all-aluminum alloy
cable and the subsequent development of the composite aluminum conductor, aluminum-alloy
reinforced cable provided new alternatives to ACSR. As with most new products, particularly in
applications as critical as electrical transmission and distribution, acceptance of the new alloy
conductor was slow. In recent years, however, the recognized electrical improvements of alloy
conductors over ACSR has led to an increasing trend of usage in aluminum alloy and composite
aluminum-aluminum alloy cables.
More recently, many innovative conductor designs have been developed to address the changing
needs of the electrical utility industry. New alloys have been developed to provide thermal stability,
increased conductivity, vibration resistance and other specific characteristics. With each change there
is a compromise. With each compromise there is a new design opportunity.

5. 4POWER CABLES
Conductor design and/or selection for transmission and distribution lines has become a science. The
selection of the optimum conductor type and size for a given transmission or distribution line design
requires a complete understanding of the characteristics of all the available conductor types. This
understanding must encompass more than just the current carrying capability or thermal performance
of a conductor. It must include a systems approach to conductor selection: line stability versus current
loading; economic operation versus thermal loading; conductor creep and resultant sag under high
temperature and adverse mechanical loading; conductor strength as determined by component metal
stress-strain performance and metal fatigue characteristics are just a few of the system design
parameters to be evaluated.
CONDUCTORS
 Objects that allow electrical charge to flow easily.
CONDUCTORS USED IN OVERHEAD TRANSMISSION LINE
There is no unique process by which all transmission and/or distribution lines are designed. It is clear,
however, that all major cost components of line design depend upon the conductor electrical and
mechanical parameters.
1. COPPER
 High electrical conductivity
 Greater tensile strength
 Always used in hard drawn form as stranded conductor
 High current density
 Durable
 High scrap value
 Higher cost
 Non availability
2. ALUMINIUM
 Cheap and light (compared to copper)
 Copper is three time heavier than al.
 Smaller conductivity and tensile strength (compared to copper)
 Conductivity – 61% of copper
 Diameter of conductor – 1.26 times of copper
 Specific gravity – 2.71 gm/cc (copper – 8.9gm/cc)

6. 5POWER CABLES
 Higher co-efficient of linear expansion (sag is greater)
3. Galvanized steel
 Very high tensile strength
 Smaller sag hence extremely long spans
 Smaller sag hence smaller high towers used
 Cheapness (main consideration)
 Transmitting small power over a small distance
4. Cadmium copper
 Copper alloyed with cadmium
 Adding 1% or 2% cadmium to copper
 Increase the tensile strength by 50%
 Conductivity is reduce only 15%
 Use for long span
CATEGORIES OF OVERHEAD CONDUCTOR
(A) Homogeneous Conductors:-
1. Copper
2. AAC ( All Aluminum Conductor)
3. AAAC (All Aluminum Alloy Conductor)
The core consists of a single strand identical to the outer strands. Since all the strands are the same
diameter, one can show that the innermost layer always consists of 6 strands, the second layer of 12
strands, etc., making conductors having 1, 7, 19, 37, 61, 91, or 128 strands.
(B) Non Homogeneous Conductors:-
1. ACAR (Aluminum Conductor Alloy Reinforced)
2. ACSR (Aluminum Conductor Steel Reinforced)
3. ACSS (Aluminum Conductor Steel Supported)
4. AACSR (Aluminum Alloy Conductor Steel Reinforced)
the strands in the core may or may not be of the same diameter. In a 30/7 ACSR conductor the
aluminum and steel strands are of the same diameter. In a 30/19 ACSR they are not. Within the core
or within the outer layers, however, the number of strands always increases by 6 in each succeeding
layer. Thus, in 26/7 ACSR, the number of layers in the inner layer of aluminum is 10 and in the outer
layer 16.
There are four major types of overhead conductors used for electrical transmission and distribution.
1. AAC - All Aluminum Conductor
2. AAAC - All Aluminum Alloy Conductor
3. ACSR - Aluminum Conductor Steel Reinforced

7. 6POWER CABLES
4. ACAR - Aluminum Conductor Aluminum-Alloy Reinforced
AAC (All Aluminum Conductors)
All Aluminum Conductor, sometimes referred to as ASC, Aluminum Stranded Conductor, is made up
of one or more strands of 1350 Alloy Aluminum in the hard drawn H19 temper. 1350 Aluminum Alloy,
previously known as EC grade or electrical conductor grade aluminum, has a minimum conductivity of
61.2% IACS. Because of its relatively poor strength-to-weight ratio, AAC has had limited use in
transmission lines and rural distribution because of the long spans utilized. However, AAC has seen
extensive use in urban areas where spans are usually short but high conductivity is required. The
excellent corrosion resistance of aluminum has made AAC a conductor of choice in coastal areas.
Features
 AAC is made up of one or more strands of hard drawn 1350 Aluminum Alloy.
 AAC has had limited use in transmission lines and rural distribution because of the long spans
utilized.
 Good Conductivity -61.2% IACS
 Good Corrosion Resistance
 High Conductivity to Weight Ratio.
 Moderate Strength
Typical Application
 Short spans where maximum current transfer
is required.
 The excellent corrosion resistance of
aluminum has made AAC a conductor of
choice in coastal areas.
 Because of its relatively poor strength-to-
weight ratio, AAC has seen extensive use in urban areas where spans are usually short but
high conductivity is required.
 These conductors are used in low, medium and high voltage overhead lines.
AAAC (All Aluminum Alloy Conductors)

8. 7POWER CABLES
A high strength Aluminum-Magnesium-Silicon Alloy Cable was developed to replace the high strength
6/1 ACSR conductors. Originally called AAAC, this alloy
conductor offers excellent electrical characteristics with a
conductivity of 52.5% IACS, excellent sag-tension
characteristics and superior corrosion resistance to that of
ACSR. The temper of 6201 is normally T81.
6201 aluminum alloy conductors are typically sold as O.D.
equivalents for 6/1 and 26/7 ACSR constructions. The O.D.
equivalent 6201 conductors have approximately the same
ampacity and strength as their ACSR counterparts with a
much improved strength-to-weight ratio. 6201 conductors
also exhibit substantially better electrical loss characteristics than their equivalent single layer ACSR
constructions. However, the thermal coefficient of expansion is greater than that of ACSR. As with
AAC conductors, the maximum short circuit temperature of 6201 must be kept below 340°C to
prevent dangerous conductor annealing.
As compared to ACSR, AAAC's ligher weight, comparable strength and current carrying capacity,
lower electrical losses and superior corrosion resistance have given this conductor wide acceptance
as a distribution conductor. It has found limited use, however, as a transmission conductor.
AAAC are made out of high strength Aluminum-Magnesium-Silicon alloy.
AAAC with different variants of electrical grade Alloys type 6101 and 6201.
These conductors are designed to get better strength to weight ratio and offers improved electrical
characteristics, excellent sag-tension characteristics and superior corrosion resistance when
compared with ACSR.
Equivalent aluminum alloy conductors have approximately the same ampacity and strength as their
ACSR counterparts with a much improved strength-to-weight ratio, and also exhibit substantially
better electrical loss characteristics than their equivalent single layer ACSR constructions. The
thermal coefficient of expansion is greater than that of ACSR.
As compared to conventional ACSR, lighter weight, comparable strength & current carrying capacity,
lower electrical losses and superior corrosion resistance have given AAAC a wide acceptance in the
distribution and transmission lines.
Features
 High strength to weight ratio
 Better sag characteristics
 Improved electrical properties
 Excellent resistance to corrosion
 Specifications
 Higher Tensile Strength
 Excellent Corrosion Resistance
 Good Strength to Weight Ratio
 Lower Electrical Losses
 Moderate Conductivity –52.5% IACS
Typical Application
 Transmission and Distribution applications in corrosive environments, ACSR replacement.
ACAR (Aluminum Conductor Al. Alloy Reinforced)

9. 8POWER CABLES
ACAR combines 1350 and 6201 aluminum alloy strands to provide a transmission conductor with an
excellent balance of electrical and mechanical properties. This conductor consists of one or more
layers of 1350-H19 aluminum
strands helically wrapped over one
or more 6201-T81 aluminum alloy
wires. The core may consist of one
or more 6201 strands. The primary
advantage of the ACAR conductor
lies in the fact that all strands are
interchangeable between EC and
6201, thereby permitting the design
of a conductor with an optimum
balance between mechanical and
electrical characteristics. In effect,
ACAR is a composite aluminum-
aluminum alloy conductor which is
designed for each application to
optimize properties. Inverse ACAR
conductors are also available with the harder 6201 aluminum alloy wires being on the outer surface of
the conductor and the 1350 aluminum making up the heart of the conductor.
Aluminum Conductor Alloy Reinforced (ACAR) is formed by concentrically stranded Wires of
Aluminum 1350 on high strength Aluminum-Magnesium-Silicon (AlMgSi) Alloy core.
The number of wires of Aluminum 1350 & AlMgSi alloy depends on the cable design.
Even though the general design comprises a stranded core of AlMgSi alloy strands, in certain cable
constructions the wires of AlMgSi Alloy strands can be distributed in layers throughout the Aluminum
1350 strands.
ACAR has got a better mechanical and electrical properties as compared to an equivalent conductors
of ACSR,AAC or AAAC.
A very good balance between the mechanical and electrical properties therefore makes ACAR the
best choice where the ampacity , strength , and light weight are the main consideration of the line
design.
These conductors are extensively used in overhead transmission and distribution lines.
Features
 Improved strength to weight ratio
 Improved mechanical properties
 Improved electrical properties
 Excellent resistance to corrosion Specifications
 Balance of Mechanical & Electrical
 Excellent Corrosion Resistance
 Variable Strength to Weight Ratio
 Higher Conductivity than AAAC
 Custom Designed, diameter equivalent to ACSR most
common.
Typical Application
 Used for both transmission and distribution circuits.
AACSR – Aluminum Alloy
Conductor Steel Reinforced
AACSR Is an ACSR with the 1350 aluminum wires
replaced by 6201-T81 aluminum alloy wires. The high

10. 9POWER CABLES
tensile strength of the 6201-T81 wires combined with the high strength of steel provides an
exceptionally high strength conductor with good conductivity. AACSR conductors have approximately
40% to 60% more strength than comparable standard ACSR conductors of equivalent stranding, with
only an 8-10% decrease in conductivity. AACSR is available with all core types specified for use with
standard ACSR.
AACSR is a concentrically stranded conductor composed of one or more layers of Aluminum-
Magnesium-Silicon alloy wire stranded with a high-strength coated steel core.
The core may be single wire or stranded depending on the size. Core wire for AACSR is available
with Class A, B or C galvanizing; or aluminum clad (AW).
Additional corrosion protection is available through the application of grease to the core or infusion of
the complete cable with grease.
Features
 Offers optimal strength for line design
 Improved strength to weight ratio
 Ideal for extra long spans and heavy load conditions
 Excellent resistance to corrosion
ACSS – Aluminum Conductors Steel Supported
ACSS conductor was designed for use as a replacement conductor in upgrading existing transmission
and distribution lines with minimum capital outlay. The premise of design is higher conductor
operating temperature without detrimental annealing of
the aluminum in standard ACSR causing a loss of
strength in the aluminum. ACSS conductor is an
aluminum-steel composite conductor resembling
standard ACSR in appearance, stranding and overall
diameter. This is the extent of their similarities
however. ACSS uses 1350-0 (fully annealed)
aluminum strands with 63.0% conductivity rather than
the traditional 1350-H19 hard drawn aluminum used in
standard ACSR which possesses 61.2% IACS
conductivity. The steel core may be made of
conventional or extra high strength steel core wire.
Compared to an equal size ACSR, ACSS has a lower
resistance, lower breaking strength, lower creep
elongation and lower elastic modulus. SSAC can be
operated at temperatures as high as 250°C without loss of strength and can be strung at higher
unloaded percentage tensions because of its good self damping characteristics.
ACSS has seen limited use in the United States. Even though ACSS has better conductivity, a higher
operating temperature and
improved damping characteristics
when compared to conventional
ACSR, it has a lower breaking
strength, typically yielding greater
initial and final sags. It is, however,
a good conductor to consider for
line upgrades if the calculated
present worth of electrical losses
shows a savings over line
conversion cost.

11. 10POWER CABLES
ACSS is a composite concentric-lay stranded conductor with one or more layers of hard drawn and
annealed 1350-0 aluminum wires on a central core of steel.
In an ACSS ,under normal operating conditions, the mechanical load is mainly derived from the steel
core as aluminum in fully annealed stage does not contribute much towards the mechanical strength.
Steel core wires are protected from corrosion by selecting an appropriate coating of the wire like
galvanizing, mischmetal alloy coating or aluminum clad. The type of coating is selected to suit the
environment to which the conductor is exposed and operating temperature of the conductor
ACSS are suitable for operating at high temperature without losing the mechanical properties.
The final sag-tension performance is not affected by the long term creep of aluminum.
Features
 Improved conductivity
 High current carrying capacity
 Very low sag at high temperature
 High degree of immunity to vibration fatigue
 Better self damping property
ACCC – Aluminum Conductor Composite Core
Aluminum Conductor Composite Core (ACCC) is a concentrically stranded conductor with one or
more layers of trapezoidal shaped hard drawn and annealed 1350-0 aluminum wires on a central core
of high strength Carbon and glass fiber composite.
The ACCC Conductor uses a carbon fiber core that is 25% stronger and 60% lighter than a traditional
steel core.
This allows with the help of trapezoidal
shaped strands the ability to increase
the conductor’s aluminum content by
over 28% without increasing the
conductor’s overall diameter or weight.
Features
 Excellent Sag properties
 Increased current carrying
capacity
 High operating temperature

12. 11POWER CABLES
 Excellent strength to weight ratio
 Highly energy efficient.
ACSR (Aluminum Conductor Steel Reinforced)
Aluminum Conductor Steel Reinforced, a standard of the electrical utility industry since the early
1900's, consists of a solid or stranded steel
core surrounded by one or more layers of
strands of 1350 aluminum. Historically, the
amount of steel used to obtain higher strength
soon increased to a substantial portion of the
cross-section of the ACSR, but more recently,
as conductors have become larger, the trend
has been to less steel content. To meet
varying requirements, ACSR is available in a
wide range of steel content - from 7% by
weight for the 36/1 stranding to 40% for the
30/7 stranding. Early designs of ACSR such as
6/1, 30/7, 30/19, 54/19 and 54/7 strandings
featured high steel content, 26% to 40%, with
emphasis on strength perhaps due to fears of
vibration fatigue problems. Today, for larger-
than-AWG sizes, the most used strandings are
18/1, 45/7, 72/7, and 84/19, comprising a
range of steel content from 11% to 18%. For
the moderately higher strength 54/19, 54/7,
and 26/7 strandings, the steel content is 26%,
26% and 31%, respectively. The high-strength ACSR 8/1, 12/7 and 16/19 strandings, are used mostly
for overhead ground wires, extra long spans, river crossings, etc.
The inner-core wires of ACSR may be of zinc coated
(galvanized) steel, available in standard weight Class
A coating or heavier coatings of Class B or Class C.
Class B coatings are about twice the thickness of
Class A, and Class C coatings about three times as
thick as Class A. The inner cores may also be of
aluminum coated (aluminized) steel or aluminum clad
steel. The latter produces a conductor designated as
ACSR/AW in which the aluminum cladding comprises
25% of the area of the wire, with a minimum coating
thickness of 10% of the overall radius. The reinforcing
wires may be in a central core or distributed
throughout the cable. Galvanized or aluminized coats
are thin, and are applied to reduce corrosion of the
steel wires. The conductivity of these thin coated core
wires is about 8% IACS. The apparent conductivity of
ACSR/AW reinforcement wire is 20.3% IACS.

13. 12POWER CABLES
Aluminum Conductor Steel Reinforced (ACSR) is concentrically stranded conductor with one or more
layers of hard drawn 1350-H19 aluminum wire on galvanized steel wire core.
The core can be single wire or stranded depending on the size.
Steel wire core is available in Class A ,B or Class C galvanization for corrosion protection.
Additional corrosion protection is available through the application of grease to the core or infusion of
the complete cable with grease.
The proportion of steel and aluminum in an ACSR
conductor can be selected based on the mechanical
strength and current carrying capacity demanded by
each application.
ACSR conductors are recognized for their record of
economy, dependability and favorable strength /
weight ratio. ACSR conductors combine the light
weight and good conductivity of aluminum with the high tensile strength and ruggedness of steel.
In line design, this can provide higher tensions, less sag, and longer span lengths than obtainable
with most other types of overhead conductors.
The steel strands are added as mechanical reinforcements.
ACSR conductors are recognized for their record of economy, dependability and favorable strength /
weight ratio.
ACSR conductors combine the light weight and good conductivity of aluminum with the high tensile
strength and ruggedness of steel.
In line design, this can provide higher tensions, less sag, and longer span lengths than obtainable
with most other types of overhead conductors.
The steel strands are added as mechanical reinforcements.
The cross sections above illustrate some common stranding.
The steel core wires are protected from corrosion by galvanizing.
The standard Class A zinc coating is usually adequate for ordinary environments.
For greater protection, Class B and C galvanized coatings may be specified.
The product is available with conductor corrosion resistant inhibitor treatment applied to the central
steel component.
Features
 High Tensile strength
 Better sag properties
 Economic design
 Suitable for remote applications involving long spans
 Good Ampacity
 Good Thermal Characteristics
 High Strength to Weight Ratio
 Low sag
 High Tensile Strength
Typical Application
 Commonly used for both transmission and distribution circuits.
 Compact Aluminum Conductors, Steel Reinforced (ACSR) are used for overhead distribution
and transmission lines.
Trap Wire Constructions:-
o AAC/TW (Trapezoidal Shaped 1350-H19 Aluminum Strands)

14. 13POWER CABLES
o ACSR/TW (Trapezoidal Shaped 1350-H19 Aluminum Conductor -Galvanized –Zinc or AW
Coated Steel Core Wires)
o ACSS/TW (Trapezoidal Shaped 1350-O Aluminum Conductor-Zinc –5% Mischmetal
Aluminum Alloy or AW Coated Steel Core wires)
Comparison of ACSR/TW Type Number with Equivalent Stranding of ACSR
Type Number Conventional ACSR Stranding
3 36/1
5 42/7
6 18/1
7 45/7
8 84/19
10 22/7
13 54/7
13 54/49
13 24/7
16 26/7
The equivalent stranding is that stranding of conventional ACSR that has the same area of aluminum
and steel as a given ACSR/TW type. The ACSR/TW type number is the approximate ratio of the area
of steel to the area of aluminum in percent.
(a) ACSR/AS – Aluminum Conductor, Aluminum Clad Steel Reinforced
ACSR/AS or ACSR/AWare concentrically stranded conductors with one or more layers of hard drawn
1350-H19 aluminum wires on Aluminum Clad steel wire core.
The core can be single wire or stranded depending on the size.
The mechanical properties of ACSR/AS conductors are similar to ACSR conductors but offers
improved ampacity and resistance to corrosion because of the presence of aluminum clad steel wires
in the core.
These conductors are better replacement for ACSR conductors where corrosive conditions are
severe.
Features
 Good mechanical properties
 Improved electrical characteristics
 Excellent corrosion resistance
 Better Sag properties

15. 14POWER CABLES
(b) ACSS/AW – Aluminum Conductors –Aluminum Clad Steel Supported
ACSS/AW or ACSS/AS is a composite concentric-lay stranded conductor with one or more layers of
hard drawn and annealed 1350-0 aluminum wires on a central core of aluminum clad steel core.
In an ACSS/AW ,under normal operating conditions, the mechanical load is mainly derived from the
steel core as aluminum in fully annealed stage does not contribute much towards the mechanical
strength.
Aluminum Clad steel has got an excellent resistance towards corrosion.
ACSS/AW are can be safely operated upto 250oC continuously without losing the mechanical
properties.
The final sag-tension performance is not affected by the long term creep of aluminum.
Features
 Improved conductivity
 High current carrying capacity
 Suitable for high temperature
 Excellent corrosion resistance
 Very low sag at high temperature
 High degree of immunity to vibration fatigue
 Better self damping property
(c) ACSR/TW – Trapezoidal Shaped 1350-H19 wire Aluminum Conductor, Steel-
Reinforced
Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductor, Steel-Reinforced (ACSR/TW)
is a concentrically stranded conductor , made with trapezoidal shaped 1350-H19 wires over a high
strength steel core.
There are two possible design variants. In one case ACSR/TW conductors are designed to have an
equal aluminum cross sectional area as that of a standard ACSR which results in a smaller conductor
diameter maintaining the same ampacity level but reduced wind loading parameters.
In the second design, diameter of the conductor is maintained to that of a standard ACSR which
results in a significantly lower conductor resistance and increased current rating with the same
conductor diameter.
manufactures ACSR/TW with Galvanized steel ( in Class A, Class B & Class C), Zn-5Al mischmetal
coated steel or Aluminum clad steel core.
Features
 High Tensile strength
 Better sag properties
 Reduced drag properties
 Low wind and ice loading parameters
 suitable for remote applications involving long spans
(d) ACSS/TW – Shaped Wire Aluminum Conductors Steel Supported
Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductor, Steel-Supported (ACSS/TW)
is a concentrically stranded conductor with one or more layers of trapezoidal shaped hard drawn and
annealed 1350-0 aluminum wires on a central core of steel.
ACSS/TW can either be designed to have an equal aluminum cross sectional area as that of a
standard ACSS which results in a smaller conductor diameter maintaining the same ampacity level
but reduced wind loading parameters or with diameter equal to that of a standard ACSS which results
in a significantly higher aluminum area, lower conductor resistance and increased current rating.
ACSS/TW is designed to operate continuously at elevated temperatures, it sags less under
emergency electrical loadings than ACSR/TW, excellent self-damping properties, and its final sags
are not affected by long-term creep of aluminum.
ACSS/TW also provides many design possibilities in new line construction: i.e., reduced tower cost,
decreased sag, increased self-damping properties, increased operating temperature and improved
corrosion resistance.

16. 15POWER CABLES
The coating of steel core is selected to suit the environment to which the conductor is exposed and
operating temperature of the conductor.
Features
 High Operating temperature
 Improved current carrying capacity
 Better sag properties
 Excellent self-damping properties
 Reduced drag properties
 Low wind and ice loading parameters
SMOOTH BODY CONDUCTORS
Some cables are designed to produce a smooth outer surface and reduce overall diameter. This
smaller diameter reduces the ice and wind loading encountered during severe weather, thereby
reducing the pole/tower loading or allowing longer design spans. Smooth body conductors are of two
types - compact conductors or trapezoidal shaped wire compact conductors, i.e., TW conductors.
Compact Conductors - Compact overhead conductors are typically available in both AAC and
ACSR with diameter reductions ranging from 8% to 11%. AAC conductors are available in a size
range of #8 AWG through 1000 kcmil with standard stranding as listed in ASTM. Compact ACSR
conductors are available only in sizes #6 AWG through 336.4 kcmil in constructions with a single steel
core wire.
Compact conductors are manufactured
by passing the stranded cable through
powerful compacting rolls or a
compacting die. The strands are
deformed, to the degree they loose their
circularity, partially filling the interstrand
voids and the outer surface of the
conductor becomes a relatively smooth
cylinder. The resulting reduction in overall
diameter not only reduces the ice and

17. 16POWER CABLES
wind loading characteristics of the conductor but also reduces the stress gradient at the conductor
surface.
150% / 200% ACSR - The terms 150% and 200% ACSR refer to a family of single layer (6/1)
constructions of ACSR that have 150% and 200% of the strength of the equivalent construction
standard ACSR while exhibiting approximately the same overall diameter. The 150% and 200%
smooth body ACSR was developed to provide a conductor with a substantial increase in ultimate
strength as compared to standard 6/1 ACSR constructions. This is accomplished by using a larger
steel core wire and drastically flattening the aluminum strands to create a smooth cylindrical
conductor surface.
150% and 200% smooth body ACSR is fabricated by passing the composite stranded cable through a
die or rolls so designed to flatten the aluminum strands and fill the interstices which exist in
conventional stranded ACSR. This brings about a reduction in overall cable diameter which means a
lower ice and wind load and greater strength to loaded weight ratio.
These conductors were primarily designed for use on rural distribution lines. The reduced diameter
and extra high strength provide substantial design and operational advantages for the longer spans of
a rural distribution line serving sparcely populated areas subject to severe cold weather conditions.
Trapezoidal Shaped Wire Conductors - Shaped wire compact conductors made from
trapezoidal (TW) shaped wires is a relatively new conductor design. These conductors can be
provided in AAC, AAAC and ACSR constructions and are designated as types AAC/TW, AAAC/TW
and ACSR/TW.
Conventional conductor designs have
traditionally used round wires. The use of
technology to design and produce
trapezoidal wires (TW) provides conductor
designers with an alternative to
conventional round strand conductor
designs. The use of trapezoidal wire
designs yields compact conductors with
less void area and a reduced outside diameter.
With conventional ACSR strandings, the number of aluminum and steel strands uniquely define the
ratio of steel area to aluminum area. For example, all 26/7 ACSR constructions have the same ratio of
steel area to aluminum area of about 16%. However, with TW strands the number of aluminum and
steel strands do not necessarily define a unique steel to aluminum ratio. Therefore the designation of
"type" has replaced the stranding designation to more accurately identify TW conductors. For example
a 795 kcmil-26/7 ACSR "Drake" has a TW counterpart designated 795 kcmil Type 16, ACSR/TW. The
aluminum area and steel area of both conductors are identical. The use of TW shaped aluminum
strands will cause the ACSR/TW to have a smaller diameter.
An alternate design concept is to specify ACSR/TW conductors with equivalent overall diameters to
conventional ACSR constructions. In this case, the diameter is matched to that of the standard ACSR
while maintaining the same ratio of steel to aluminum by area. Since the aluminum area is increased,
the steel area must be increased to maintain the proper area ratio.

18. 17POWER CABLES
If a reduced diameter TW construction is selected, the diameter is reduced by approximately 10%
thereby reducing the design ice and wind loading on the conductor. If an equal diameter TW
construction is selected, the aluminum area is increased by approximately 20% - 25% providing a
decrease in AC resistance of 15% - 20% and increasing the current carrying capacity 8% to 10%.
The use of trapezoidal wires provides a more compact conductor design with mechanical properties
at least equal to that of conventional ACSR. Since ACSR/TW designs have the same steel-to-
aluminum ratios as their equivalent ACSR constructions, stress-strain and creep data developed for
conventional strandings of ACSR can be used to predict sag and tension design data for ACSR/TW
conductor constructions.
TW conductor installation requires no special tools, equipment or training.
VIBRATION RESISTANT CONDUCTOR
A wind induced motion resistant conductor, VR conductor is designed for use as a bare overhead
conductor in areas subject to aeolian vibration and galloping due to wind and ice. Use of this
conductor allows it to be strung to the maximum allowable NESC design tensions without the need for
additional vibration protection.
VR conductor is composed of two identical conductors twisted together with a nine-foot left-hand lay,
giving the conductor a spiraling "figure 8" shape. This spiraled shaped disrupts the forces created by
steady cross winds by presenting a continuously changing projected conductor diameter to the wind.
By disrupting the forces created by turbulent wind flow, conductor vibration is prevented. This unique
spiral shape, together with less torsional stiffness and varying bending stiffness also reduces or
eliminates conductor galloping due to combined ice and wind loads.

19. 18POWER CABLES
VR conductor can be made of component conductors of AAC, AAAC, ACAR, ACSR, AAC/TW or
ACSR/TW meeting the appropriate requirements. The type component or subconductor selected
should be based on strength and thermal requirements. Constructions are available in all conductor
sizes and are suitable for both distribution and transmission requirements.
VR conductor is typically manufactured and sold as an alternate to standard round conductor. The
total circular mil area of both component conductors equals the circular mil area of the VR
construction. Conductor constructions are normally referred to by the registered code name of the
component conductors followed by the VR designation, i.e., "Ibis/VR".
SELF DAMPING CONDUCTOR
Sometimes called SDC (Self Damping Conductor), ACSR/SD is a concentric lay stranded, self
damping conductor designed to control aeolian type vibration in overhead transmission lines by
internal damping. Self damping conductors consists of a central core of one or more round steel wires
surrounded by two layers of trapezoidal shaped aluminum wires. One or more layers of round
aluminum wires may be added as required.
Self damping conductor differs from conventional ACSR in that the aluminum wires in the first two
layers are trapezoidal shaped and sized so that each aluminum layer forms a stranded tube which
does not collapse onto the layer beneath when under tension, but maintains a small annular gap
between layers. The trapezoidal wire layers are separated from each other and form the steel core by
the two smaller annular gaps that permit movement between the layers. The round aluminum wire
layers are in tight contact with each other and the underlying trapezoidal wire layer.
ACSR/SD has been very effective in reducing aeolian vibration on transmission lines. However, most
contractors charge a premium for installation because of special hardware requirements and
specialized stringing methods.

20. 19POWER CABLES
BUNDLED CONDUCTOR
A bundled conductor arrangement with two or more conductors in parallel, spaced a short distance
apart is frequently used for HV and EHV transmission lines. Many electrical reasons can be cited in
favor of bundled conductors. From the stand point of current density per unit area, smaller conductors
have higher possible current densities, thus greater metal efficiency. The use of multiple conductors
per phase having the same total area as a single conductor will operate at lower temperatures
yielding lower resistances and losses for equal loads.
Multiple conductors offer significant improvements in reactance over a single conductor of equal area.
The inductive reactance of a two conductor bundle is only about 50% of the reactance for a single
conductor having the same circular mil area as the bundled pair. Obviously, the greater the spacing
between subconductors, the lower the reactance.
Although important, the electrical advantages of
bundled conductors may not be the most important
factor influencing their use. The concerns of corona and
radio noise may dictate the use of bundled conductors
since corona loss of a conductor is a function of the
voltage gradient at the conductor surface. The subjects
of corona and RIV have been well investigated and will
not be further discussed here.
The number and size of conductors per phase have not
been standardized. It is dependent upon many factors.
Today conductor bundles are a standard design
practice for transmission lines designed to operate at
345 kV or higher.
Any of the above discussed conductors including VR
Cable, can be used as subconductors for bundle conductor designs. This presents the transmission
design engineer with limitless design options.

21. 20POWER CABLES
Surface Finishes
The surface of a conductor must be relatively clean and smooth to perform satisfactorily as an
electrical conductor. However, special surface treatments or finishes may be required to reduce
reflectivity or impart other desired special appearance, or in some cases aerodynamic, characteristics
to a conductor or conductor assembly. The most common surface treatment and one normally
required for conductors used for transmission and distribution lines crossing undeveloped Federal
Government park lands is one to reduce the reflectivity of aluminum conductors. This type of surface
finish is referred to as non-specular.
NON-SPECULAR CONDUCTOR - The term non-specular is used to infer that the surface of an
aluminum conductor, any type aluminum conductor, has been either mechanically or chemically
treated to produce reduced reflectivity. The conductor surface must have a smooth matte gray finish
which blends naturally and unobtrusively with the environment.
This non-specular finish is typically achieved by passing the finished conductor through a deglaring
machine (a type of sandblast machine) in which the conductor surface is blasted with a very fine mild
abrasive grit producing a dull matte gray finish. The reflectivity and color of the finished cable is
specified by ANSI C7.69 Specifications.
The abrasive action of the blast media is extremely mild and in no way affects the mechanical
characteristics of the conductor. The ampacity of current carrying capability of non-specular
conductors is slightly increased because the emissivity of the conductor is increased from
approximately 0.23, for bright shiny conductors, to approximately 0.42 because of the darker matte
gray surface. An increase in current carrying capacity in the range of 5% can be achieved, for the
same temperature rise, due to this increase in surface emissivity.
Other surface finishes providing benefits such as improved aerodynamic characteristics have been
reported. The merits of such finishes must be evaluated to determine if lasting economic benefits
exist.
STANDARD SIZES OF CONDUCTOR FOR LINES OF VARIOUS
VOLTAGES
The following sizes have now been standardised by CEA for transmission lines of different voltages--
(i) For 132 KV lines : 'Panther' ACSR having 7-strands of steel of dia 3.00 mm and 30-Strands of
Aluminium of dia 3.00 mm
(ii) for 220 KV lines : 'Zebra' ACSR having 7-strand of steel of dia 3.18 mm and 54-Strands of
Aluminium of dia 3.18 mm.
(iii) for 400 KV lines : Twin 'Moose' ACSR having 7-Strands of steel of dia 3.53 mm and 54-
Strands of Aluminium of dia 3.53 mm.

22. 21POWER CABLES
CHOICE OF OVERHEAD CONDUCTOR
depend upon:
 Power Delivery Requirements
 Current Carrying Capacity
 Electrical Losses
 Line Design Requirements
 Distances to be Spanned
 Sag and Clearance Requirements
 Environmental Considerations
 Ice and Wind Loading
 Ambient Temperatures
 Strength
 Weight
 Diameter
 Corrosion Resistance
 Creep Rate
 Thermal Coefficient of Expansion
 Fatigue Strength
 Operating Temperature
 Short Circuit Current/Temperature
 Thermal Stability
 Cost
UNDERGROUND CABLE
An underground cable essentially consists of one or more conductors covered with suitable
insulation and surrounded by a protecting cover.
In general, a cable must fulfil the following necessary requirements :
 The conductor used in cables should be tinned stranded copper or aluminium of high
conductivity. Stranding is done so that conductor may become flexible and carry more
current.
 The conductor size should be such that the cable carries the desired load current without
overheating and causes voltage drop within permissible limits.
 The cable must have proper thickness of insulation in order to give high degree of safety and
reliability at the voltage for which it is designed.
 The cable must be provided with suitable mechanical protection so that it may withstand the
rough use in laying it.
 The materials used in the manufacture of cables should be such that there is complete
chemical and physical stability throughout.

23. 22POWER CABLES
CONSTRUCTION OF UNDERGROUND CABLES
(i) Cores or Conductors:- A cable may have one or more than one core (conductor) depending
upon the type of service for which it is intended. The conductors are made of tinned copper or
aluminium and are usually stranded in order to provide flexibility to the cable.
(ii ) Insulation:- Each core or conductor is provided with a suitable thickness of insulation, the
thickness of layer depending upon the voltage to be withstood by the cable. The commonly used
materials for insulation are impregnated paper, varnished cambric or rubber mineral compound.
(iii ) Metallic sheath:- In order to protect the cable from moisture, gases or other damaging
liquids (acids or alkalies) in the soil and
atmosphere, a metallic sheath of lead
or aluminium is provided over the
insulation as shown in Fig.
(iv ) Bedding:- Over the metallic
sheath is applied a layer of bedding
which consists of a fibrous material like
jute or hessian tape. The purpose of
bedding is to protect the metallic
sheath against corrosion and from
mechanical injury due to armouring.
(v ) Armouring:- Over the bedding,
armouring is provided which consists of
one or two layers of galvanised steel
wire or steel tape. Its purpose is to
protect the cable from mechanical
injury while laying it and during the
course of handling. Armouring may not
be done in the case of some cables.
(vi) Serving:- In order to protect armouring from atmospheric conditions, a layer of fibrous material
(like jute) similar to bedding is provided over the armouring. This is known as serving.

24. 23POWER CABLES
INSULATING PROPERTIES FOR CABLES
The insulating materialsused in cables should have the
following properties :
(i) High insulation resistance to avoid leakage current.
(ii) High dielectric strength to avoid electrical breakdown of the cable.
(iii) High mechanical strength to withstand the mechanical handling of cables.
(iv) Non-hygroscopic i.e., it should not absorb moisture from air or soil. The moisture tends to
decrease the insulation resistance and hastens the breakdown of the cable. In case the
insulating material is hygroscopic, it must be enclosed in a waterproof covering like lead
sheath.
(v) Non-inflammable.
(vi) Low cost so as to make the underground system a viable proposition.
(vii)Unaffected by acids and alkalies to avoid any chemical action.
CLASSIFICATION OF CABLES
Cables for underground service may be classified in two ways according to
(i ) the type of insulating material used in their manufacture
(ii ) the voltage for which they are manufactured.
However, the latter method of classification is generally preferred, according to which cables can be
divided into the following groups :
(i ) Low-tension (L.T.) cables — upto 1000 V
(ii ) High-tension (H.T. ) cables — upto 11,000 V
(iii ) Super-tension (S.T.) cables — from 22 kV to 33 kV
(iv ) Extra high-tension (E.H.T.) cables — from 33 kV to 66 kV
(v ) Extra super voltage cables — beyond 132 Kv

25. 24POWER CABLES
Low-tension (L.T.) cables:-
A cable may have one or more than one core
depending upon the type of service for which it is
intended. It may be (i) single-core (ii) two-core (iii)
three-core (iv) four-core etc. For a 3-phase
service, either 3-single-core cables or three-core
cable can be used depending upon the operating
voltage and load
demand. The cable has ordinary construction
because the stresses developed in the
cable for low voltages (upto 6600 V) are generally
small. It consists of one circular core of tinned
stranded
copper (or aluminium) insulated by layers of
impregnated paper. The insulation is surrounded
by a
lead sheath which prevents the entry of moisture
into the inner parts. In order to protect the lead
sheath from corrosion, an overall serving of compounded fibrous material (jute etc.) is provided.
Cables for 3-phase servise:-
1. belted cables – upto 11 kv
2. screened cables – from 22 kv to 66 kv
3. pressure cables – beyond 66 kv
Belted cables:-
 The cores are insulated from each
other by layers of impregnated
paper.
 Another layer of impregnated
paper tape, called paper belt is
wound round the grouped
insulated core.
 The cores are generally stranded
and may be of non circular shape
to make better use of available
space.
Screened cables:-

26. 25POWER CABLES
Conclusion :-
The selection of the optimum conductor type and size for a given line consists of finding that
conductor which results in the lowest present net worth cost spread over the life of the line. The
transmission line design engineer is confronted with choosing a conductor type from among this
bewildering assortment. This choice must be based on basic conductor parameters.
It is clear that all the major cost components of a transmission line depend upon conductor physical,
mechanical and electrical parameters. A list of these basic parameters are:
 conductor diameter
 weight per unit length
 conductivity of material(s)
 crossectional area(s)
 modulus of elasticity
 rated breaking strength
 coefficient(s) of thermal expansion
 cost of material(s)
 maximum unloaded design tension
 resistance to vibration and/or galloping
 surface shape/drag coefficient
 fatigue resistance
These basic parameters are not necessarily independent of one another. However, certain
parameters can be varied independently over a range of design considerations.
It is the hope of this writer that a better understanding of available conductor types and materials will
provide a better base for future conductor selections.

27. 26POWER CABLES
REFERENCES:
1. Douglass, Dale A., Economic Measures of Bare Overhead Conductor Characteristics, IEEE Paper
86 TD 502-9 PWRD.
2. Kennon, Richard E., Douglass, Dale A., EHV Transmission Line Design Opportunities for Cost
Reduction, IEEE Paper 89 TD 434-2 PWRD.
3. Hudson, G.T., Cofer, D.B., 6201 Aluminum Alloy: A Superior Overhead Conductor, Southwire
Company, October 1982.
4. EHV Transmission Line Reference Book, Published in 1968 by the Edison Electric Institute, written
and edited by Project EHV.
5. Transmission Line Reference Book, 345 KV and Above / Second Edition, Copyright 1982 by the
Electric Power Research Institute Inc., Prepared by Project UHV.
6. Electrical Conductor Handbook, Third Edition 1989, The Aluminum Association.
7. Dziedzie, E., EHV Conductors, Copyright 1969, Kaiser Aluminum and Chemical Corporation.
8. Aluminum, Vol. II Design and Application, Copyright 1967 by the American Society for Metals,
prepared by engineers, scientists, and metallurgists of the Aluminum Company of America.
9. Edwards, A.T., Livingston, A.E. Self-damping Conductors for the Control of Vibration and Galloping
of Transmission Lines, IEEE Paper 68 C 59 PWR.
10. Kirkpatrick, L.A., McCulloch, A.R., Pue-Gilchrist, A.C., Ten Years of Progress with Self-Damping
Conductor, IEEE Paper F 79 736-0, presented at the IEEE PES Summer Meeting.
11. Principle of power system by V K Mehta.