1. VIDHYAPEETH
Institute of Science & Technology, Bhopal
Presented By : -
Surojit mahato
EX branch

2. INTRODUCTION
 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.

3. CONTENTS
 General Constructions of Cable.
 Types of Cables
 Belted Cables
 Screened Type Cables
 H-Type cables
 S.L. cables
 Super Tension Cables
 Oil Filled Cables
 Gas Pressure Cables
 Advantages
 Disadvantages

4. GENERAL CONSTRUCTION
1. Conductor or Core
2. Insulation
3. Metallic Sheath
4. Bedding
5. Armouring
6. Serving

5. TYPES OF CABLES
 The types of cables basically
decided based on the voltage
level for which it is
manufactured and material
used for the insulation such
as paper, cotton, rubber etc.
the classification of cables
according to the voltage
levels is,
 Low Tension Cables (L.T.
Cables)
 Medium and High tension
Cables (H.T. Cables)

6. BELTED CABLES
 These cables are used for the
voltage level up to 11 kV. The
construction of belted cable is
shown in fig.
 The cores are not in circular
shape.
 The cores are insulated from
each other by use of
impregnated paper.
 The gaps are filled with fibrous
material like jute.
 The belt is covered with lead
sheath.

7. SCREENED TYPE CABLES
 These cables are used for the voltage levels
of 22 kV and 33 kV. The two types of
screened cables are:
 H-Type cables
 S.L. Type cables

8.  H- Type cables :
 Designed by M. Hochstetler
and hence named H-type
cable.
 No paper belt in this type of
cable.
 Each conductor is insulated
with a paper, covered with a
metallic screen.

9.  S.L. Cables :
 S.L. leads for Separate Lead
Screened Cables.
 Each lead is insulated with an
impregnated paper than
covered by separate sheath
lead.

10.  Advantages :
 Due to individual lead sheath, core to core fault
possibility gets minimized.
 Electrical stresses are radial in nature.
 Bending of cable is easy.
 Disadvantages :
 Uses solid insulation only like paper.
 Mechanical shock can cause voids.

11. SUPER TENSION (S.T.) CABLES
 The S.T. cables are intended
for 132 kV to 275 kV voltage
levels.
 In such cables, the following
methods are specially used to
eliminate the possibility of void
formation:
 Instead of solid type
insulation, low viscosity oils under
pressure is used for impregnation.
 Using inert gas at high pressure in
b/w the lead sheath & dielectric.

12. OIL FILLED CABLES
 In case of oil filled
cables, the channels or
ducts are provided within
or adjacent to the
cores, through which oil
under pressure is
circulated.
 It consists of concentric
standard conductor but built
around a hollow cylindrical
steel spiral core, which acts
as a channel for oil.

13.  Advantages :
 Thickness of insulation required is
less.
 Thermal resistance is less.
 Possibility of voids is completely
eliminated.
 Temperature range is high.
 Perfect impregnation is possible.
 Disadvantages :
 Initial cost is very high.
 Long lengths are not possible.
 Oil leakage is serious problem.
 Complicated maintenance.

14. GAS PRESSURE CABLES
 An inert gas like N at high
pressure is introduced lead
sheath and dielectric.
 Gas like SF6 is also used in
cables.
 Pressure is about 12-15
atmosphere.
 Working power factors is
also high.

15.  Advantages :
 These can carry 1.5 times of the normal load current.
 Maintenance cost is small.
 No reservoirs or tanks required.
 Power factor is improved.
 Ionization and possible void completely eliminated.
 Disadvantages :
 The only disadvantage is that the initial cost is
extremely high.

16. VIDHYAPEETH Campus
Have a nice day . . . . Thank you