The document provides an overview of underground cables, detailing their definitions, requirements, and properties of insulation materials. Key benefits of underground cables include reduced damage risk, low maintenance costs, and enhanced voltage regulation. It highlights commonly used insulating materials and concludes with a summary of key topics discussed.

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NAME :
SUBJECT CODE : EE-504
TOPIC : UNDERGROUND CABLES
DURATION : 50 MIN
TEACHING AIDS : DIAGRAMS,PPTS
HEMA SRINIVAS CHALAPAKA
LECTURER
SUB TOPIC : DEFINE CABLES
MBTS GOVT. POLYTECHNIC, GUNTUR.
POWER SYSTEM –II
TRANSMISSION AND DISTRIBUTION
DEPARTMENT OF TECHNICAL EDUCATION
ANDHRA PRADESH
DESIGNATION :
ELECTRICAL & ELECTRONICS ENGINEERING
BRANCH :
INSTITUTE :
V - SEMESTER
YEAR / SEMESTER :
SUBJECT :

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OBJECTIVES
OBJECTIVES
• Introduction to Underground Cables
• Definition of a Cable
• Requirements of Underground Cables
• Properties of Insulation materials used for Cables
On completion of this period, you would be able to
know

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Known to Unknown
Known to Unknown
•Can you identify the things shown below?
F1G.1

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Introduction to Underground Cables
Introduction to Underground Cables
• Electric power can be distributed by underground
cables.
Advantages of underground cables :
• Less liable to damage through storms and lightening.
• Low maintenance cost.
• Less chances of faults.
• Better voltage regulation.
• Good general appearance.

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Definition of a Cable
Definition of a Cable
• An underground cable essentially consists of one or
more conductors covered with suitable insulation
surrounded by a protecting cover.
A simple cable
F1G.2.

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Definition of a Cable
Definition of a Cable
• In a simple way, a cable can be seen as a combination of
conductor, insulator and protective cover.

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Requirements of Underground Cables
Requirements of Underground Cables
• Conductor used in cables should be copper or aluminium.
• Conductor must be stranded and tinned.
• Conductor size should be such that the cable carries the
desired load current.
• Cable should cause voltage drop within permissible limits.
(Contd…)

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Requirements of Underground Cables
Requirements of Underground Cables
• Cable must have proper thickness of insulation to give
high degree of safety.
• Cable must be provided with suitable mechanical
protection.
• Materials of a cable must be free from chemical and
physical throughout.

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Properties of Insulation materials used for
Properties of Insulation materials used for
Underground Cables
Underground Cables
• High insulation resistance to avoid leakage current.
• High dielectric strength to avoid electrical breakdown.
• Good mechanical strength to have flexibility.
• Low coefficient of thermal expansion.
• Non-inflammable.
(Contd…)

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Properties of Insulation materials used for
Properties of Insulation materials used for
Underground Cables
Underground Cables
• Low permittivity.
• Immune from acid and alkalies.
• Non-hygroscopic i.e. should not absorb moisture.
• Low power factor.
• Cost should be economical.

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Most commonly used Insulating materials in
Most commonly used Insulating materials in
Underground Cables
Underground Cables
• Impregnated paper
• Poly Vinyl Chloride
• Butyl Rubber
• Polythene
• Cross linked Polyethylene

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Summary
We have discussed about
• Definition of Cables.
• Requirements of Underground Cables.
• Properties of Insulation materials used for
Cables.

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1. Cable is a combination of
(a) Conductors
(c) Conductors and Insulation
(b) Insulation
(d) None of the above
Quiz

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2. Insulating materials used in cables are
(a) Poly Vinyl Chloride
(c) Polythene
(b) Impregnated Paper
(d) All of the above
Quiz

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Frequently asked questions
Frequently asked questions
• Define Cable.
• List any four requirements of Cables.
• List the materials used for insulating cables.