Cable Presentation for Drum Project

7/28/2019 Cable Presentation for Drum Project

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www.ieema.org [email protected]


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Power Delivery System Electricity from the Generating Site (the Power Plant) is delivered to residential,

commercial and industrial customers through a system of wires (overhead) orcables (underground), switches, protection & control devices and transformers


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PresentationonElectrical Cables&Accessories


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Conductor

(CU / AL)

Wires

Conductor

Armoured

Cables

Laid Up

Cables

Inner

Sheathed

cables

FinishedCables

Cores

Drawing

Bunching

Stranding

Laying Up

(For Multi Core)

Sheathing

Taping Armouring

Testing and

Packing

Insulation

Sheathing

Manufacturing Process of Electrical Power Cables


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Finest Electrolytic Grade 99.9 % Pure

Copper or Aluminium

The process reduces the wire rods to

Specified or desired wire diameter.

Annealing & Tinning of fine copper wires.

Wire DrawingManufacturing Process

Conductor

(CU / AL)

Wires

Drawing


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StrandingThe individual strands are bunched together

to form a conductor of specified size.

Manufacturing Process

Conductor

(CU / AL)

Wires

Conductor

Drawing

Bunching

Stranding


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Extruders

Triple Extrusion line for HT cables

Manufacturing ProcessInsulation



Manufacturing Process : Copper ScreeningOnly for HT Cables above 6.6 KV Grade

Copper tape with the number/color marking is applied over the cores.

Where required Water blocking tape can also be provided.

Copper tape Screening & Copper wire screening.



Lay up to 100 cores with Extruded/taped inner sheath

Manufacturing ProcessLaying Up

Conductor

(CU / AL)

Wires

Conductor

Laid UpCables

Cores

Drawing

Bunching

Stranding

Laying Up

(For Multi Core)

Insulation


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Emboss/Print on line on outer sheath.

Manufacturing ProcessSheathing

Conductor

(CU / AL)

Wires

Conductor

Armoured

Cables

Laid Up

Cables

Inner

Sheathedcables

Finished

Cables

Cores

Drawing

Bunching

Stranding

Laying Up

(For Multi Core)

Sheathing

Taping Armouring

Insulation

Sheathing



Quality treated wooden / steel Drums for winding the finished cables

before final testing & delivery.

Manufacturing ProcessConductor

(CU / AL)

Wires

Conductor

Armoured

Cables

Laid Up

Cables

Inner

Sheathed

cables

Finished

Cables

Cores

Drawing

Bunching

Stranding

Laying Up

(For Multi Core)

Sheathing

Taping Armouring

Testing and

Packing

Insulation

Sheathing



Four major parameters of cable design to

illustrate the proper design

Conductor

Insulation

Armouring

Sheathing

Emphasis On Design



The heart of the cable is the Conductor.

Conductor



Example of selection of the no of strands in a conductor.

WHY 19 STRANDS ARE REQUIRED

FOR 70 SQ.MM. CONDUCTOR?

NO OF STRAND:-19 SIZE:-2.24mm1

d =2.24mm.

d=PITCH CIRCULAR DIAMETER

FOR FIRST LAYER = 2X2.24mm =

4.48mm

NO. OF WIRES IN FIRST LAYER =

dX3.14/d = 4.48X3.14/2.24

6 WIRE3 1 2

d =2Xd

Conductor


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When conductors are not properly shaped, they have gaps , sharp edges

in between the wires, which may lead to failures , after a period of time.

Gaps also increase Conductor Resistance

A properly designed conductor

is smooth and compact.

Conductor



If the compaction is not proper, it can lead to air gaps, which increase

conductor resistance.

A Bad Design of Conductor Can Cause

3% to 9% Transmission loss,Failure due to Sharp

Edges.

Conductor



A good Insulation should have:

High insulation resistance

High dielectric strength

Good mechanical properties

Tenacity & elasticity should not be affected by

chemicals.

Should be non hygroscopic.

Insulation



Insulation Uniformity of Insulation Thickness & Eccentricity

Avoids increase in charging current and

lessens the voltage drop

If dielectric is not uniform, it leads to increase

in the capacitance of the conductor and

resultant higher temperature.


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Laying up & Inner Sheath The cores are laid up, along with fillers & suitable

binding tape, ensuring circularity. It is an

international practice to have filler insertedbetween the cores, to prevent displacement of

the cores in manufacturing as well as in laying of

cable at site.


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Laying up & Inner Sheath Many times cores are laid up with nylon/cotton

twine, which results in cores getting damaged,

which effects not just the insulation thickness

but also, the overall performance of the cable.


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Laying up & Inner Sheath CABLE WITH NON HYGROSCOPIC

POLYPROPYLENE TAPE & FILLERS

PP tape & Filler has very high melting point i.e.

160 C.

Has very high insulation resistance property

i.e. 150 Mohm/km

Works as water barrier, prevents water

penetration inside the cable.

Less flexibility than other types of

polyethylene, which prevents the cores from

displacement in the cable.


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ArmouringApart from mechanical protection, an important feature of

Armour design is to provide effective conductance of

earth fault current. When designing an armoured cable,

the selection of minimum number of armour wire/stripsplays a very important role


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ArmouringExample : 3.5 C X 240 SQ.MM A2XFY cable.

Min. 34 strips require for 100% coverage.

And with this the armour resistance at 20 C

will be 1.62 ohm/km & short circuit current

carrying capacity will be 4.2 kA/Sec,

where as the Max requirement as per IS 7098 part I

is 1.64 ohm/km

If we use 30 strips in place of 34,

there will be a gap and the armour

resistance will be increased to 1.79 ohm/km &

short circuit current carrying capacity

will come down to 3.7 kA/sec


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Armouring protects the cable from mechanical damage.

Maintain minimum 95% coverage to protect the cable from any

mechanical damage because of sharp edges.

Badly Armoured Cables

Armouring


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This Protects the Overall Cable

Embossing / printing options on the outer sheath.

Outer Sheathing


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Stringent Quality checks at each and every level.

Raw materials.

In Process.

Finished goods.

Emphasis On Quality

EMPHASIS ON QUALITY : TESTING LABS


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Raw Material Testing

The major raw materials in a Cable are :-

Copper/Aluminium Rods

PVC/XLPE Compounds

Armour Wires/Strips

Emphasis On Quality


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Copper/Aluminium Rods

Tensile Strength

Resistivity

Purity

Surface Finish

Diameter

Aluminium Rods

Emphasis On Quality : R.M.Testing


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XLPE & PVC Compounds

Tensile Strength & Elongation

Hot set

Volume Resistivity

Ageing

Thermal Stability

Density Galvanized Steel Wires / Strips

Tensile Strength & Elongation

Dimensions

Zinc Coating (Dip Test)

Torsion/Winding

Resistivity

Emphasis On Quality : R.M.Testing


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In process quality checks are performed at each and every stage of

manufacturing

Stage wise details of Quality checks performed are shown in the next

set of folios.

Diameter

Surface finish

Tensile/Wrapping test for Aluminium

Annealing/Elongation test for Copper

Resistivity

Emphasis On Quality

Wire Drawing : R. M. Testing


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No. of strands

Stranding Sequence

Surface finish

Resistance

Conductor screening (HT)

Thickness

Tensile strength & Elongation

Hot Set test

Surface finish

Type of Compound

Dia. Over conductor

Dia. Over insulation & Insulation screening (HT)

Stranding : Quality Checks

Insulation : Quality Checks


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No. of wires / Diameter of wire (Wire Screening)

Gap between wires (Wire Screening)

Lay length (Taping / Wire screening)

Tape Overlap (Taping)

Sequence of Laying

Diameter over laid up cores

Lay length

Laying Up Quality Checks

Copper Screening : Qulaity Checks


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Thickness

Diameter over inner sheath

Surface finish

Inner Sheath : Quality Checks

Armouring : Quality Checks Dimension of wire/strip

Diameter over armouring

Gap between wires/strip

No. of wires/Strip

Direction of lay and lay length


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Thickness

Diameter over outer sheath

Tensile strength & Elongation

Surface finish & Marking/Embossing

Colour of sheath & Type of Compound

Outer Sheath : Quality Checks


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Emphasis On Quality Checks Finished Goods testing

Routine tests are carried out as per relevant standards on each cable

length.

Type tests are carried out for each LOT (One manufacturing length)

Acceptance tests and Inspections can be arranged as per requirements ofcustomers.

Testing Facilities should include :

Partial Discharge

FRLS Testing

Oxygen Index

Smoke Density

Halogen Gas

High Voltage / Impulse Voltage


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Packing & Marking

Testing of End sealing.

Testing of packing and wooden drums

Inspection for marking and scripts

Emphasis On Quality Packing Drums

Inspection of Marking on sheath


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CABLE LAYING&INSTALLATION


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Cable installation involves selection of cable route, mode of installation

i.e. underground, in duct or cable ladder/ trays, associated accessories and

man power

For cable laying it is very essential to get acquainted with the visible as

well as hidden obstacles and following activities are recommended prior tothe actual laying work

Inspection of cable route

Trial holes to check thermal resistivity & underground

obstacles.

Excavation (Trenching) & preparation of cable bed Laying of necessary pipes

Drum handling & cable pulling equipment including pay

off jacks

Arrangement of filling.

Back filling

Planning


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Inspection of cable route :The cable route is first inspected as per the main plan for visibleobstruction such as trees, manholes, road crossing etc.

Trial Holes:After inspection of the cable route, it is advisable to have theknowledge of the underground obstruction. Trial holes are generally

taken at every 50 meters interval along the planned cable route up to

10 cm below the planned depth of laying. The route is then inspected

for underground obstruction e.g. water lines, drainage lines,

telephone cables, power cables or other utilities etc.

After this the cable route is finalized keeping in view that it should

be straight as far as possible and proper depth is permissible. It is

then marked suitably for trenching


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Clearances : The desired minimum clearances are as under- Power to Control cables : 0.2 m

Power to communication cables : 0.3 m

Power cables to gas/water main : 0.3 m

Inductive influence on sensitive control cable on account of near

by power cable should also be checked.

Width of trench : The width of trench depends on no & diameter of cables to be laid. For

HV & EHV cables the width of excavation is generally as under-

No. of Cables HV Cables EHV Cables

3 0.65 m 0.8 m

4 0.85 m 1.05 m


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Sand bedding: Sand bedding of minimum 10 cm is provided for the cables laid

directly in ground for protection. The grain size of sand should

preferably be less than 8 mm. The material with high volume weight

ratio has a good distribution among grain sizes and it has normally

low thermal resistivity, even when it has lower moisture.

Laying of Ducts/ pipes: Steel, cast iron, plastics, cements or earthenware ducts or

cable ducting blocks are used for cables crossing

roads/railway tracks. Spare ducts for future expansions

should also be provided and should be properly sealed off.Buried ducts or ducting blocks should project into footpath

or up to the edge of road, where there is no footpath, to

permit smooth entry of cable without un-due bending. The

duct/pipe should be mechanically strong to withstand the

impact due to traffic when laid across road/railway tracks.


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Laying of Ducts/ pipes (Continued): The pipe/duct are generally laid at depth 1.0 & 1.2 metres

across road and railway racks respectively. The diameter of

duct or pipe should be at least 1.5 times the outer diameter of

cable.

Single core cable should never be laid individually in steel

ducts. However, it is permissible to lay all three cables of same

system in one duct.


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Transportation of cable drum: The cable drum must be handled properly to avoid any damageto cable during transportation. It is important that cable drum

stands on the flanges during transportation, well fixed to the

transport vehicle. Loading of drum should be done by crane or

forklift. A ramp or crane should be used for unloading cabledrums from vehicle. Where it is not possible, a temporary ramp

with approx. inclination 1:3 to1:4 should be constructed and

cable drums should then be rolled over the ramp by means of

ropes and winches. An additional sand bed at foot of the ramp is

also helpful to brake the rolling of cable drum. Where it is

necessary to roll the cable on ground, it should be done slowly

and carefully. The drum should always be rolled in the direction

of arrow marked on the drum to avoid unwinding & loosening of

cable in the drum as shown in the figure.


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Transportation of cable drum:


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Pulling of cable: The cable drum shall be placed such that there is minimum inconvenience.

Cable drum is normally placed on jacks at starting point, in such a way that

direction arrow points to the opposite direction of the pulling, and a wire

winch at the other end of the pulling distance of the trench. The pulling wire

can be connected to the cable either by a cable stocking or directly to the

conductor in such a manner that water or soil cannot enter the cable. Except

for wire armoured cables, the cable is normally pulled by the conductor with

pulling force limiting to the following -

Aluminum conductor : 30 N/mm2

Copper conductor : 50 N/mm2

The cable should be pulled from the top of the drum. To prevent crossing of

turns on the drum due to sudden stop in pulling, a brake should be arranged

at the cable drum as shown in figure and a man should be placed there to

operate this brake rapidly.


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Pulling of cable drum:


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Pulling of cable: With temperature below 30C, the cables should be warmed before the

laying out, otherwise the bending can damage the insulation/protective

covering of cables. The cable laying should be carried out swiftly so that

the cable does not cool down too much.

Warming of cable may be achieved by storing the cable drum for

adequately longer period, not less than 24 hours, in a heated building or in

a tent with hot air heaters

To protect the cable from damage during pulling out, cablerollers should be used, placed at suitable intervals. Bends

must be arranged very carefully and cable is not allowed to

bend beyond the limit specified as mention here under.

Closely spaced and well fixed angle rollers are skid plates

should be used at all corners


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MINIMUM PERMISSIBLE BENDING RADIUS

PILC Cables PVC/XLPE Cables

Cable Voltage single Multi single Multi

rating core core core core

Up to 1.1 kV 20 D 15 D 15 D 12 D

3.3 kV to 11 kV 20 D 15 D 15 D 12 D

22 kV & 33 kV 25 D 20 D 20 D 15 D

Above 33 kV - - 20 D

- D = outer diameter of cable

Pulling of cable:


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Filling:After laying the cable, sand should be filled in the trench to completelysurround the cable. The grain size of sand shall be less than 8 mm. The

thickness of sand in all direction of the cable surface should normally not

be less than 10 cm.Backfilling:Normally the backfill consists of material excavated earlier from the trench.However, bigger stones or pieces of rock should be removed.

Extra protection:Important feeders and cables at places where high digging activity is

expected can be further protected by means of tubes, slabs or troughs

The tubes of non-magnetic material are mainly used at road crossing etc.

The tube diameter should not be less than 2 times the cable diameter. The

current rating of cables laid in tube is reduced up to 80% of the cable

rating in ground. The tubes can be filled with material e.g. Bentonite,

having thermal resistivity equal to the ground, to avoid reduction in ground

rating.


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In trenches, normally extra protection is achieved by providing flat

concrete slabs of size selected according to the expected damage.

Generally slab is 50 mm thick and of sufficient width to cover the

cables. The slabs are placed directly on the sand as shown here

below


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A very efficient protection against cable damage can be obtained by

using concrete troughs. The trough should be completely filled with

the sand.


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Warning tape (Specially for EHV cables):A pre warning tape, e.g. of yellow PVC, should be laid in the ground

around o.2 to 0.4 metre under the surface and at least o.4 mm above the

cable. In a trench with several cables, the warning tape should not be

spaced more than 0.15 metres apart and the outermost cable should

always be covered by warning tapes.

Special precautions for single core cables:Except for EHV cables, the spacing between three cables laid in one

plane should generally be not less than the cable diameter. When the

cables are arranged in a duct or on rack, the cables should be secured by

non-magnetic, non-corrosive clamps.When the cable run is several kilometer long, the cable should be

transposed at 1/3rd and 2/3rd of the total route length.

For cables in trefoil formation, non-magnetic clamps are not essential

and steel, copper, Aluminum or plastic tape may be used to bind the cable

trefoil


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BIRD CAGING


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If the drum is kept on the flange or lifted from one

side & cable unwound, there is all likelihood of twists

in the armour, which would cause deformation

of cores & outer-sheath.

This process of deformation is called

BIRD CAGING &

is normally perceived as a manufacturing defect

which is normally a HANDLING defect.


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This can be prevented by unwinding the cable by loading the

drum on jacks & pulling in the proper direction with stocking

or pulling eye.

Proper Handling of cables is very important, both from

safety as well as long life of the installation.

The most common causes of cable failure are due to

mishandling of the product at installation stage.

In the following slides we show you some of the effects

of mishandling of the cables.


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Recommendation for Installation


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GROUP RATING FACTOR FOR SINGLE CORE

CABLES LAID IN TREFOIL FORMATION

B. Cables laid on Racks/Trays in covered trench withremovable covers where air circulation is restricted, trefoilsare separated by 2 cable dia. horizontally and the traysare in tiers with 300 mm. gap between them.

NO. OFRACKS/TRAYS IN

TIERS

NO. OF TREFOILS IN HORIZONTAL FORMATION

1236

1 2 3

0.950.900.880.86

0.900.850.830.81

0.880.830.810.79

NUMBER OFTREFOILS IN

GROUP

SPACING BETWEEN TREFOILS3.3 TO 22 KV CABLES

33 KV CABLES

TOUCH

ING

15

cm

30

cm

45

cm

TOUCH

ING

15

cm

30

cm

45

cm

2345

0.780.680.610.56

0.810.710.650.61

0.850.770.720.68

0.880.810.760.73

0.800.680.620.57

0.820.710.650.60

0.850.760.710.67

0.880.790.750.72

A. Cables laid in ground in horizontal formation

C. Cables laid as in 'B' but in open air


TIERS

NO. OF TREFOILS IN HORIZONTAL FORMATION

1

2

3

6

1 2 3

1.0

1.0

1.0

1.0

0.98

0.95

0.94

0.93

0.96

0.93

0.92

0.90


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GROUP RATING FACTOR MULTICORE CABLES


TIERS

NO. OF CABLES

12

36

1 2 3

0.950.90

0.880.86

6 9

0.900.85

0.830.81

0.880.83

0.810.79

0.850.81

0.790.77

0.840.80

0.780.76

B. Cables laid on cable trays exposed to air, the cables

spaced by one cable diameter and trays in tiers by 300 mm.The clearance between the wall and the cables is 25 mm.

A. Cables laid inside concrete trench with removeable

covers, on cable trays where air circulation is restricted.

The cables spaced by one cable diameter and the trays in

tiers by 300 mm. The clearance of the cable from the wall is 25 mm.

NO. OF CABLETRAYS IN

TIERS

NO. OF CABLES

1236

1 2 3

1111

6 9

0.980.950.940.93

0.960.930.920.90

0.930.900.890.87

0.920.890.880.86

C. Cables laid on cable trays exposed to air, the cables

touching and trays in tiers by 300 mm. The clearance

between the wall and the cable is 25 rnm.

NO. OF TRAYS

NO. OF CABLES

12

3

6

1 2 3

1.01.0

1.0

1.0

6 9

0.840.80

0.78

0.76

0.800.76

0.74

0.72

0.750.71

0.70

0.68

0.730.69

0.68

0.66

D. Cables laid direct in ground in horizontal formation.

NO. OFCABLES

IN GROUP

SPACING OF CALBLES

23

4

5

6

0.790.69

0.62

0.58

0.54

0.820.75

0.69

0.65

0.61

0.870.79

0.74

0.72

0.69

0.900.83

0.79

0.76

0.75

TOUCHING 15 cm 30 cm 45 cm


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RATING FACTOR

GROUNDTEMPERATURE(C)

FACTOR

15

1.12

20

1.08

25

1.03

30

1.00

35

0.96

40

0.91

45

0.87

A. Rating factors for ambient air temperature variation

AMBIENTTEMPERATURE (C)

25

1.14

30

1.10

35

1.04

40

1.00

45

0.95

50

0.90FACTOR

B. Rating factors for ground temperature variation

DEPTH OF LAYING (cm)

90

105

120

150

180or more

6 KV, 10 KV AND15 KV ALL SIZES

1.00

0.99

0.98

0.960.95

20KV AND 30 KVALL SIZES

---

1.00

0.99

0.970.96

C. Rating factors for depth of laying

( for cables laid direct in the ground)

THERMALRESISTIVITY

OF SOIL(ccm/w)

100

1.20

120

1.11

150

1.0

200

0.89

250

0.80

300

0.73FACTOR

D. Rating factors for variation in Thermal Resistivity of soil


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CABLE

ACCESSORIES


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SEPARABLE CONNECTORS

LOADBREAK

DEADBREAK

OTHER CONNECTORS

CABLE JOINTS CABLE TERMINATIONS


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Utilize permanently crimped connectors

Housings/Tubings are fully insulated,

shielded and sealed

Direct buried, vault, submersible and other

severe service applications

Units designed and tested per IS/VDE/IEEE

Standards to assure system matched

performance and ratings equal to cable

Cable Joints Overview


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Terminations &

Cable Basics


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While Cable Basics uses the CableTermination as the base example, the

same principles apply anywhere a

shielded medium or high voltage cableis terminated.

Elbows, Joints, etc.


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Conductor


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+ Insulation

+ Conductor shield

Conductor


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+ Semi-Con Shield

+ Insulation

+ Conductor shield

Conductor


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In case of p remo ldedterminat ions


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The addi t ion o f a stress contro ltube tends to smooth the

st ress concentrat ions in case

of heat shr ink term inat ion s


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Only in case of

premolded terminations


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This same cone shape

is incorporated intomost Cable Accessories


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Right angle boot is

used in case ofHeat shrink

Terminations
http://www.shrinkpolymersystems.co.uk/3cPilcBeltedTermination.pdf


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End of Session..

Documents

Cable Presentation for Drum Project