power cable intern report

8/8/2019 Power Cable Intern Report

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Parteek kansal

En. No. 070244

B.Tech Electrical Engineering

IIT Roorkee



ECKO CABLESEcko cables was first produced in 1958 and found aninstant acceptability in the market.

In 1969, Evershine - KDK Brand was introduced foreastern India market as a running mate of ECKO.

Presently, ECKO & EVERSHINE - KDK cables are being produced at three different manufacturingfacilities belonging to ECKO GROUP.



Products Building (House Wiring)&Industrial Wiring Cables

Flame Retardant Low Smoke (FRLS) Cables

Railway Signaling Cables

Control Cables

Power Cables



COMPONENTS



Conductor

Conductor is a current carrying element made up of

Aluminum or Copper with a specific cross section for

the assigned rating.



Electric Insulation Insulation is provided over the conductors to electrically

isolate them from one another.

An insulated conductor is termed as Core. In twin,

three & multi-core cables, the cores are laid up

together with a suitable lay; the outer most layer has

right-hand lay and the successive layers are laid with

opposite lay direction.



Inner sheath (bedding) Cables with stranded cores are provided with Inner Sheath

applied either by extrusion or by wrapping.

It is ensured that the shape is as circular as possible. Inner

Sheath is so applied that it fits closely on the laid up cores

& it should be possible to remove it without damage to the

insulation.



Armour A wire, strip or a tape applied helically over the cable, to

protect the cable from penetration by sharp objects,

crushing forces, and damage from rodents or boring

insects, is termed as Armour.

Armour is applied over the insulation in case of single

core cables & over inner sheath in case of twin, three &

multi core cables.



Outer Sheath Outer sheath /Jacket is usually an extruded plastic cover

over the laid-up or armoured core. PVC is a common

sheathing material.

The colour of outer sheath is normally black.



Conductor Manuf acturing Material Selection

For efficient distribution of electric power, the conductors must be

produced from a high conductivity material. Copper and aluminum are

received as large coils of round rod.

Wire Drawing

In wire drawing, the copper or aluminum rod is drawn through a series

of successively smaller dies to reduce the rod to a wire of the desired

diameter. The quality of the wire surface depends on sufficient

drawing and reduction to eliminate surface defects.



Annealing Drawing copper or aluminum wires increases the temper of the metal.

Therefore, the wire is exposed to elevated temperatures well in excess of

emergency operating temperatures of the cable.

This is accomplished in a large oven.

Stranding Stranded conductors use a number of smaller wires the sum of which

total the desired conductor cross sectional area. The machines used in

stranding apply successive layers of strands over a central core made up

of one or a number of strands.



Nominal Cross-section(mm2)

Solid/Stranded Flexibility Class

Copper Al

--- 1.5 Solid Class1

1.5-6 2.5-10 Solid/Stranded Class1 forsolid/Class2 forstranded

10 + 16+ Stranded Class 2



Screening in Cable(Phase voltage> 1 kv)Above certain voltages, as a means of containing the electrical field within the

insulation, semiconducting screens are applied over the conductor & insulation.

Screens are provided to achieve symmetrical dielectric fields within the cable

structure & carry current during short circuit. By this it is possible to eliminate any

electrical discharges arising from air gaps adjacent to the insulation.

During the early 1960s semiconducting tapes were applied at the conductor but

these have since been superseded by an extruded layer. This has the advantage of

providing a smoother finish as it fills the interstices between the wires.

The semiconducting layer is compatible with, and bonds to, the insulation and a

nominal thickness of 0.7 mm is typical.



InsulationThe conductor shall be provided insulation through a process called extrusion.

ExtrusionCompound, in the form of pellets or strips, is fed into the back of a screw that rotates in

a barrel. The material advances down the screw and is melted during the advance.In general, the barrel is divided into zones that are individually temperature controlled.



There are some extrusions where the barrel is heated at the start of the

extrusion, but as the extrusion continues, the mechanical shear and

friction results in sufficient heat generation that barrel heating is no

longer required. In fact, depending on compound and extrusion

parameters, barrel cooling may be required. Properly executed, the

compound is all melted and forced through a die-head arrangement

that deposits the melt on the core being passed through the head. This

core may be a bare wire or cable in some stage of completion.



Nominal Areaof conductor Nominal thickness of

insulation(Ti)

Nominal thickness of

insulation

1.5 1.1 0.8

2.5 1.2 0.9

4 1.3 1.06 1.3 1.0

10 1.3 1.0

16 1.3 1.0

25 1.5 1.2

35 1.5 1.2

50 1.7 1.4

70 1.7 1.4

95 1.9 1.6

120 1.9 1.6150 2.1 1.8

185 2.3 2.0

240 2.5 2.2

300 2.7 2.4

400 3.0 2.6

500 3.4 3.0

630 3.9 3.4

800 3.9 3.4

1000 3.9 3.4

Thickness of insulationThe average thickness of insulation shall be not less than the nominal value (Ti) specified in following tables:

For PVC:

Thickness of insulation



Nominal Areaof conductor Nominal thickness of insulation(Ti) Nominal thickness of insulation

1.5 1.0 0.7

2.5 1.0 0.7

4 1.0 0.7

6 1.0 0.7

10 1.0 0.7

16 1.0 0.7

25 1.2 0.9

35 1.2 0.9

50 1.3 1.0

70 1.4 1.1

95 1.4 1.1

120 1.5 1.2

150 1.7 1.4

185 1.9 1.6

240 2.0 1.7

300 2.1 1.8

400 2.4 2.0

500 2.6 2.2

630 2.8 2.4

800 3.1 2.6

1000 3.3 2.8

For XLPE



Comparison of XLPE cables with PVC cables

The important difference is the extra toughness of insulation and, in

particular, the ability to withstand much high temperature without

deformation due to mechanical pressure. The better physical properties of

XLPE enable the insulation thickness to be reduced and hence overall size

of the cable.

The continuous temperature rating is increased from 70°C to 90°C and the

temperature for short circuit ratings for the cable from 160°C to 250°C.



CoolingSingle layers that are relatively thin may be cooled in a water trough following extrusion. In

the case of polyethylene, care must be taken to avoid too rapid a quench. This rapid cooling

can result in locked-in mechanical stresses that will result in shrink-back of the material on

the wire.

Heavier thermoplastic layers, such as encountered on primary cables, require gradient

cooling to avoid these stresses in the polyethylene.

Cooling zones are used to control the cooling process for water-cooled cables.



CORE IDENTIFICATIONCores shall be identified by different coloring of PVC insulation by adopting the following

Scheme:

1. a) 1 Core: red, black, yellow, blue or natural (non-pigmented);

b) 2 Cores: red and black;

c) 3 Cores: red, yellow and blue;

d) 4 Cores: red, yellow, blue and black;

e) 5 Cores: red, yellow, blue, black and grey; andf) 6 Cores and above: Two adjacent cores (Counting and direction core) in each layer, blue

and yellow, remaining cores Grey, or in accordance with the scheme mentioned in (2)



2. For cables having more than 5 cores, as an alternate to the provisions of (1),

the core identification may be done by numbers. In that case, the insulation of cores

shall be of the same color and numbered sequentially, starting with number 1 for the

inner layer. All the numbers shall be of the same color which shall contrast with the color

of the insulation.

LAYING UP OF CORESIn twin, three- and multi-core cables, the cores shall be laid up together with a suitable

lay; the outermost layer shall have right-hand lay and the successive layers shall be laid

with opposite lay; where necessary, the interstices shall be filled with non-hygroscopic

material.

The recommended lay-up for cores up to 100 is given in the table on the next slide.



NO. OF

CORES

LAY-UP NO. OF

CORES

LAY-UP NO. OF

CORES

LAY-UP

(1) (2) (1) (2) (1) (2)

2 2 36 0-6-12-18 70 2-8-14-20-263 3 37 1-6-12-18 71 2-8-14-20-27

4 4 38 1-6-12-19 72 2-8-14-21-27

5 5 39 1-6-13-19 73 3-9-15-20-26

6 6 40 1-7-13-19 74 3-9-15-21-26

7 1-6 41 1-7-13-20 75 3-9-15-21-27

8 1-7 42 2-8-13-19 76 3-9-15-21-28

9 1-8 43 2-8-14-19 77 3-9-15-22-28

10 2-8 44 2-8-14-20 78 4-10-15-21-28

11 3-8 45 2-8-14-21 79 4-10-16-22-27

12 3-9 46 3-9-14-20 80 4-10-16-22-28

13 3-10 47 3-9-15-20 81 4-10-16-22-29

14 4-10 48 3-9-15-21 82 4-10-16-23-29

15 5-10 49 3-9-15-22 83 4-10-17-23- 29

16 5-11 50 3-9-16-22 84 5-11-17-23-28

17 5-12 51 4-10-16-21 85 5-11-17-23-29

18 0-6-12 52 4-10-16-22 86 5-11-17-23-30

19 1-6-12 53 4-10-16-23 87 5-11-17-24-30

20 1-7-12 54 4-10-17-23 88 5-11-18-24-30

21 1-7-13 55 4-11-17-23 89 0-6-11-18-24-30

22 2-7-13 56 5-11-17-23 90 0-6-12-18-24-30

23 2-8-13 57 5-11-17-24 91 1-6-12-18-24-30

24 2-8-14 58 5-11-18-24 92 1-6-12-18-24-31

25 2-8-15 59 5-12-18-24 93 1-6-12-18-25-31

26 3-9-14 60 0-6-12-18-24 94 1-6-12-19-25-31

27 3-9-15 61 1-6-12-18-24 95 1-6-13-19-25-31

28 3-9-16 62 1-6-12-18-25 96 1-7-13-19-25-31

29 4-10-15 63 1-7-12-18-25 97 1-7-13-19-26-31

30 4-10-16 64 1-7-13-18-25 98 2-8-13-19-25-31

31 4-10-17 65 1-7-13-19-25 99 2-8-14-19-25-31

32 5-11-16 66 1-7-13-19-26 100 2-8-14-20-25-31

33 5-11-17 67 2-8-13-19-25

34 5-11-18 68 2-8-14-19-25

35 5-12-18 69 2-8-14-20-25



INNER SHEATH (COMMON COVERING)The laid-up cores shall be provided with inner sheath applied either by extrusion

or by wrapping.

Calculated diameter over

stranded cores(over)

Calculated diameter over

stranded cores (up to and

including)

Thickness of inner

sheaths(min)

---- 25 0.3

25 35 0.4

35 45 0.5

45 55 0.6

55 ---- 0.7



ARMOURING Armouring shall be applied over insulation or non-metallic part of insulation in

case of single core cables and over the inner sheath in case of multi core

cables.

The armour wires/strips shall be applied as closely as practicable.

The direction of lay of the armour shall be left hand. For double wires/strips

armoured cables, this requirement shall apply to the inner layer of wires/strips.

The outer layer shall, except in special cases, be applied in the reverse

direction to the inner layer, and there shall be a separator of suitable non-

hygroscopic material, such as plastic tape, rubber tape between the inner and

outer layers of armour wires strips.



Type of Armour1. Where the calculated diameter below armouring does not exceed 13 mm, the

armour shall consist of galvanized round steel wires. The armour of cables having

calculated diameter below armouring greater than 13 mm shall consist of eithergalvanized round steel wires or galvanized steel strips.

2. In the case single-core cables, the armouring shall be of non-magnetic

material.

3. Dimensions The dimensions of galvanized steel wires/strips shall be as

specified in following table:



Calculated diameterof cable under

armour

Nominal thickness of

steel strip

Nominal

diameter of round armour

wire

A)For all

diameters in

excess of 13

0.8 4

B)---- 13 ---- 1.40

13 25 0.8 1.6

25 40 0.8 2.0

40 55 1.4 2.5

55 70 1.4 3.15

70 ----- 1.4 4.0



OUTER SHEATHThe outer sheath shall be applied by extrusion. It shall be applied:

a) Over the non-magnetic metallic tape covering the insulation or over the nonmagnetic

metallic part of insulation screening in case of unarmoured single core cables, and

b)O

ver the armouring in case of armoured cables.The colour of outer sheath shall be black, unless any other colour is agreed to between

the purchaser and the supplier.

Thickness of Outer Sheath

Unarmoured Cables The thickness of outer sheath of unarmoured cables determined

by taking the average of a number of measurements shall be not less than the nominal

value specified in column 3 of following table and the smallest of the measured values

shall be not less the minimum value specified in column 4 of given table.



Calculated diameter under the

outer sheath

Thickness of outer sheath for

unarmoured cable

Minimum thickness of outer

sheath under armoured cables

Over Up to and

including

Nominal Minimum

---- 15 1.8 1.24 1.24

15 25 2.0 1.40 1.40

25

5 2.2 1.5 ¡ 1.5 ¡

5 40 2.4 1.72 1.72

40 45 2.¡

1.88 1.88

45 50 2.8 2.04 2.04

50 55

.0 2.20 2.20

55 ¡ 0

.2 2.

¡ 2.

¡

¡ 0 ¡ 5

.4 2.52 2.52

¡ 5 70

.¡

2.¡

8 2.¡

8

70 75

.8 2.84 2.84

75 ---- 4.0

.00

.00

Armoured Cables The thickness of outer sheath shall be not less than the minimum value specified in column 5 of above table.



TestsClassification of tests

Routine Tests

Tests made by the manufacturer on all finished cable lengths to demonstrate

the integrity of the cable.

a) Conductor resistance testb) High voltage test

Type Test

Tests required to be made before supply on a general commercial basis on

a type of cable in order to demonstrate satisfactory performance

characteristics to meet the intended application.NOTE These tests are of such a nature that after they have been made, they

need not be repeated unless changes are made in the cable materials of

design which might change the performance characteristics.



a) Tests on conductor

i) Annealing test (for copper)

ii) Tensile test (for aluminum)

iii) Wrapping test (for aluminum)

iv) Resistance test

b) Tests for round steel wire/formed steel wire (strip) armour

1) Dimensions

2) Physical tests on round/formed wire

i) Tensile strength

ii) Elongation at break

iii) Torsion test for round wires

iv) Winding test for formed

v)Resistivity



c) Test for thickness of insulation and sheath

d) Physical tests for insulation

i) Tensile strength and elongation at break

ii) Ageing in air oven

iii) Hot set test

iv) Shrinkage test

v) Water absorption (gravimetric)



e) Physical tests for outer sheath

i) Tensile strength and elongation at break

ii) Ageing in air oven

iii) Loss of mass in air

iv) Shrinkage test

v) Hot deformation

vi) Heat shock test

vii) Thermal stabilityf) Insulation resistance (volume resistivity test)

g) High voltage test

h) Flammability test



Acceptance Tests

Tests carried out on samples taken from a lot for the purpose of acceptance of the lot.

a) Annealing test (for copper),

b) Tensile test (for aluminum),

c) Wrapping test (for aluminum),

d) Conductor resistance test,

e) Test for thickness of insulation and sheath,

f) Hot set test for insulation,

g) Tensile strength and elongation at break test for insulation and sheath,

h) High voltage test, and

j) Insulation resistance (volume resistivity) test.



Optional Tests

Special tests to be carried out, when required, by agreement between the

purchaser and the supplier.a) Cold bend test for outer sheath

b) Cold impact test for outer sheath

.

power cable intern report

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