This document discusses power cables. It begins with an introduction and overview of general cable construction, including cores, insulation, metallic sheaths, bedding, armoring, and serving. It then covers the classification, properties of insulating materials, common material types used for insulation, and types of cable faults that can occur in oil impregnated paper insulated cables and extruded cables. Faults discussed include conductor-conductor, flashing, conductor-shield, serial, earth, and humid/wet faults.

1. POWER CABLES
PRESENTED BY
MUHAMMAD BILAL
SUBMITTED BY
SIR SHAJAR
MARCOUS

2.  Introduction
 General Constructions of Cable.
 Classification of Cables
 Properties of Insulating Material
 Types of materials used in insulation
 Types of cable faults
 Oil impregnated paper insulated cables
 Extruded (XLPE)cables
 Faults in OIPC and XLPE
 Conclusion
 References

3.  A power cable is an assembly of two or
more electrical conductors, usually held together with
an overall sheath. The assembly is used for
transmission of electrical power. Power cables may be
installed as permanent wiring within buildings, buried
in the ground, run overhead, or exposed.
 Flexible power cables are used for portable devices,
mobile tools and machinery.

4.  Core or Conductor
A cable may have one or more than one
core depending upon the type of service
for which it is intended.
 Insulation
The core is provided with suitable
thickness of insulation, depending upon
the voltage to be withstood by the cable.
 Metallic Sheath
A metallic sheath of lead or aluminium is
provided over the insulation to protect
the cable from moisture, gases or othes
damaging liquids
Core
Belted paper
Lead sheath
Bedding
Single wire
armoring
Overall Serving

5. Bedding
Bedding is provided to protect the metallic sheath from
corrosion and from mechanical damage due to armoring
Armouring
Its purpose is to protect the cable from mechanical injury while
laying it or during the course of handling. It consists of one or
two layers of galvanized steel wire or steel tape.
Serving
To protect armouring from atmospheric conditions, a layer of
fibrous material is provided.

6. Properties of Insulating Material
The insulating materials used in cables should have the
following properties
 High resistivity.
 High dielectric strength.
 Low thermal co-efficient.
 Low water absorption.
 Low permittivity.
 Non – inflammable.
 Chemical stability.
 High mechanical strength.
 High viscosity at impregnation temperature.
 Capability to with stand high rupturing voltage.
 High tensile strength and plasticity.

7. TYPES OF MATERIALS USED IN INSULATION
 Vulcanized India rubber
 Impregnated paper
 Silk and cotton
 rubber
 Enamel insulation
 Varnished cambric
 Polyvinyl chloride

8. 1. Low tension cable
2. Belted cable
3. Screened or H type cable
4. SL type cable (separate lead sheath cable)
5. HSL type cable (H+SL)
6.Super tension cable
(a) Oil field cable
(b) Gas pressure cable

9. 1. Paper insulated Cable (PIC)
2. PVC Cable (Polyvinyl Chloride)
3. Oil filled paper insulated Cable
4. High Pressure oil filled Cable
5. Compressed gas insulated cable
6. Vulcanized rubber Cable
7. XLPE insulated Cable (Cross linked polyethylene
insulated)

10. The following are the faults most likely to occur in Power cables:
A.Fault Conductor - conductor (parallel Fault)
• Connection between two or more
conductors.
• When two conductors of a multi-core cable
come in electrical contact with each other
due to insulation failure
TYPES OF CABLE FAULTS

11. B. Flashing fault (parallel Fault)
• Very high resistance fault.
• The flashover happens typically at some kV
and is very often located in Joints.
• The insulation resistance of this fault is
typically infinite up to the breakdown voltage.

12. C. Fault Conductor - shield (parallel Fault)
• Connection between Conductor and shield or
Conductor/Conductor and shield.
• Experience has shown, that most faults are in
this category

13. D. Serial fault (Open, Interrupt)
• Faults of this type can be very high resistive
up to infinite (complete cut).
• The reason for this being a complete cut of the
cable, or it is pulled out of the joint , which
interrupts everything, but also permits
flashovers in all possible variations.

14. E. Earth faults, sheath faults
• Faults between the metallic shield and
surrounding soil in case of plastic insulated
cables.
• Especially for these type of faults the highest
precaution must be taken when using high
voltage, this is of utmost importance, since the
voltage discharges directly to earth.

15. F. Humid / wet faults
• Humidity faults are the most difficult faults to
locate.
• Depending on the cable construction (e.g.
longitudinal water sealing) these faults can be
punctual or widespread throughout the cable.
• Other forms of humidity faults are underwater
faults. Here the water pressure prevents an
effective ignition of the fault during the HV
application.