SEMINAR

1. SEMINAR
ON
UNDERGROUNDCABLES
Presented by:
Ramesh kumar
Department OF EEE
MITS JADAN
GUIDE BY :
Mr. HITESH JAIN (Asst. Professor)
ELECTRICAL DEPARMENT
MITS JADAN,PALI

2. Contents
2
 Introduction of Underground cables
 Construction of cables
 CABLE STRUCTURE
 Classification of cables
 Properties of Insulating Material
 Insulating materials for cables
 Examples of types
 Advantages and disadvantages of cable

3. Underground cables
 An underground cable consists of one or more
conductors covered with some suitable insulating
material and surrounded by a protecting cover.
 The interference from external disturbances like
storms, lightening, ice, trees etc. should be reduced to
achieve trouble free service.
 The cables may be buried directly in the ground, or
may be installed in ducts buried in the ground.
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4. CABLE STRUCTURE
4

5. Construction of Cables
ing
The general construction of a 3-conductor cable. The various parts of
cable are :
 Cores or Conductors
 Insulation
 Metallic sheath
 Bedding
 Armour
 Serving
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6. CLSSIFICATION OF CABLES
 Low tension (L.T)  up to 1000V
 High tension (H.T)  up to 11, 000V
 Super tension (S.T)  from 22KV to 33KV
 Extra high tension (E.H.T) cables  from 33KV to
66KV
 Extra super voltage cables beyond 132KV
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7. Properties of Insulating
Material
strength.
-efficient.
rption.
y.
ble.
ility.
 High resistivity.
 High dielectric
 Low thermal co
 Low water abso
 Low permittivit
 Non – inflamma
 Chemical stab
 High mechanical strength.
 High viscosity at impregnation temperature.
 Capability to with stand high rupturing voltage.
 High tensile strength and plasticity.
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8. Insulating Materials for Cables
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• Rubber
It can be obtained from milky sap of tropical trees or
from oil products.
It has the dielectric strength of 30 KV/mm.
Insulation resistivity of 10 exp 17 ohm.cm
Relative permittivity varying between 2 and 3.
They readily absorbs moisture, soft and liable to
damage due to rough handling and ages when exposed
to light.
Maximum safe temperature is very low about 38 C

9. Insulating Materials for Cables
 XLPE Cables (Cross Linked Poly-ethene)
 This material has temperature range beyond 250 – 300 C
 This material gives good insulating properties
 It is light in weight, small overall dimensions, low dielectric constant
and high mechanical strength, low water absorption.
 permit conductor temperature of 90 C and 250 C under normal and
short circuit conditions.
 suitable up to voltages of 33 KV.
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10. Insulating Materials for Cables
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 Rubber
 XLPE cable
 Vulcanized India Rubber
 Impregnated Paper
 Varnished Cambric
 Polyvinyl chloride (PVC)

11. Extra High Tension Cable
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12. Low Tension Cable
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13. 3- Core belted
Cable
3- Core
Cables
(H-Type)
3- Core Cables
(S.L. Type)
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14. Advantages & Disadvantages
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Advantages
◦ Better general appearance
◦ Less liable to damage through storms or lighting
◦ Low maintenance cost
◦ Less chances of faults
◦ Small voltage drops
Disadvantages
◦ The major drawback is that they have greater installation
cost and introduce insulation problems at high voltages
compared with equivalent overhead system.

15. End
Of
The
slide
THANKS TO ALL
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