Cable and Insulators

Cable and Insulator

CABLES MERIT AND DEMERIT OF CABLE

1.

It has good impact on over all power system effectiveness and continuity of power guarantee.

2.

More reliable

3.

More cost per Kw per km

4.

Tapping is difficult

5.

Less liability to damage due to natural calamity

6.

Difficult and Expensive joint

7.

Requires Small apace

8.

Low reactance

9.

Better regulation

10.

Sharp bending possible

11.

Long life

12.

High over load capacity

13.

Access for repairing

14.

High short circuit rating

15.

Good vibration resistance

16.

Water and weather proof

17.

good corrosion resistance

18.

High safety against hazards

19.

Good esthetics

20.

Can be used in power, control telecom.

21.

High cost

22.

Fault finding difficult

Shavak Nanavati Technical Institute

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Cable and Insulator

ADVANTAGES OF ALUMINIUM CONDUCTOR

1.

Cheaper in cost

2.

Lighter in weight

3.

Poor conductivity

4.

Low tensile strength

5.

Larger cross sectional area required for same current.

6.

Linear coefficient of expansion is 1.4 time more than copper

7.

Low melting point

8.

Easily affected by corrosion

9.

Jointing difficult.

ADVANTAGE OF COPPER CONDUCTOR

1.

High conductivity

2.

High tensile strength

3.

High corrosion resistance at normal atmosphere

4.

Lesser cross sectional area for same current

5.

It is quit homogeneous.

6.

Durable

7.

High scrap value















Cable and Insulator

CLASSIFICATION CLASSIFICATION OF CABLES AS PER SIZE (Sq. mm) 1.5,

2.5,

4,6

16,

25,

35,

50,

70,

95,

185, 200, 225, 300, 400, 500, 500

and

630

BASED ON VOLTAGE VOLTAGE 1.

Low tension

Up to 1.1 kV

2.

High tension

Up to 11 kV

3.

Extra High tension

Up to 33 kV

4.

Ultra High tension

Up to 132 kV

BASED ON APPLICATION 1.

Wiring cable

2.

Power cable

3.

Signal and control

4.

Flexible cable

5.

Co axial

6.

Trailing Cable

AS PER CONDUCTOR 1.

Copper

2.

Aluminium

3.

Iron

AS PER CORE 1.

Single core

2.

Double core

120, 150,















Cable and Insulator

6.

Six core

7.

Ten core

AS PER CONSTRUCTION OF CONDUCTOR

1.

Un stranded

2.

Stranded

3.

Braided

4.

Hollow

AS PER SHAPE

1.

Circular

2.

Sector

3.

Concentric Cylinder

4.

Oval

AS PER MECHANICAL PROTECTION 1.

Armored

a) Wire Armored b) Strip Armored c)Tape Armored 2.

Unarmored

AS PER INSULATION

1.

VIR (SBR)

2.

Butyl rubber

3.

Silicon rubber

4.

Paper















Cable and Insulator

8.

CSP

9.

PTFE

10.

XLPE

AS PER PROTECTING COVERING 1.

2.

Braiding a)

Cotton

b)

Silk

c)

Jute

d)

Cambric

e)

Asbestos

Sheathing a)

Metallic i) Lead Alloy

b)

Non metallic i)

PVC, VIR

AS PER SPECIAL ARRANGEMENT 1.

Bedding

2.

Serving

3.

Screening

4.

Shielding PROPERTIES OF CABLE I NSULATION NSULATION

1.

It should have high specific resistance

2.

It should be tough and flexible















Cable and Insulator

5.

It should be non inflammable

6.

It should not be affected by acid and alkalis.

7.

It should be capable of withstanding high rupturing voltages.

8.

It should have low viscosity at working temperature (for solid cable only)

9.

It should have low water absorption

10.

It should have low permittivity

11.

It should have high mechanical strength

12.

It should provide high degree of safety. safety. TYPE OF INSULATION

1.

PAPER

∆

Thickness 07. – 1.9 mm

∆

To make the stress line radial, Hochestader in 1920 applied a grounded screen above conductor insulation.

∆

This cable used above 11 kv

∆

Paper being hygroscopic has to be protected with lead sheath, this make cable costlier

∆

Hence to replace lead, plastic cables were develop since 1960

∆

Belted cable used up to 11 11 kv TYPE OF PAPER CABLE

∆

Belted cable

∆

H type cable

∆

SL cable

















Cable and Insulator

PARTS PARTS O F PAPER INSULATED CABLE ∆

Conductor

∆

Insulation

∆

Screening

∆

Bedding

∆

Sheathing

∆

Armoring

∆

Serving 2. PVC INSULATED AND PVC SHEATHED

∆

Power cables 1.1 kv to 11 kv is available in1000 mm 2 In single core and 500 mm 2 in multi core.

∆

Normally aluminum conductor up to size 10 2 mm are solid circular in cross section and size above 10 2 mm are stranded.

∆

Conductors above 25 sq. mm are normally sector shaped.

∆

Unaffected by water

∆

Laid directly under water

∆

Over Loaded for shorter period

















Cable and Insulator

3. XLPE : CROSS LINKED POLY POLY ETHYLENE ∆

High continuous current rating

∆

High short circuit rating

∆

High emergency load

∆

Low dielectric loss

∆

Low charging current

∆

Easy laying

∆

High safety against vibration and mechanical damage.

∆

Good operating temperature. Continuous – 90° & short circuit – 250°

∆

Excellent bending properties.

∆

Can bear heavy fluctuating load

∆

High chemical resistant. CONSTRUCTION

∆

Conductor

















Cable and Insulator

APPLICATION

Power station Industrial plants Chemical plants

4. FRLS : FIRE RESISTANCE RESISTANCE LOW SMOKE ∆

Used where high degree of safety of personnel and equipment is required

∆

Ability to restrict flame propagation

∆

Low smoke to provide better visibility

∆

Low acid & gas emission

∆

Low toxic gas emission

5.

PTFE :- POLY POLY TETRA FLORO ETHYLENE

∆

Excellent thermal

∆

Good electrical and mechanical properties

∆

Poor resistance to corona

















Cable and Insulator

∆

Low dielectric constant

∆

Low P.F

∆

High dielectric strength

∆

Low moisture absorption

∆

It is homogeneous but not void free

8.

EPR – ETHYLENE PROPELENE RUBBER

9.

CHLOROPREN RUBBER

High resistance towards oil and water Poor Tensile Tensile s trength Poor Abrasion resistance It is used for sheath. 10. SILICONE RUBBER ∆

Used in high temperature operation

∆

Continuous operation

150 – 180 ° c

∆

Emergency over load

250 ° c

∆

Short circuit

350 ° c

















Cable and Insulator

APPLICATION :-

Furnace, oven, steel rolling mill, foundries, HV equipment, thermal power station. COMPARISION OF INSULATING MATERIALS

THERMAL PROPERTIES.

MATERIAL

MAX. TEMP

E M. O/L

SHORT. CKT TEMP.

THERMAL. RESISTVITY 0 C/CM/W

HOT DEFORMATION RESISTANCE AT 150 ° c

XLPE

90

130

250

350

GOOD

PE

70

90

150

350

MELT MELT

EPR

90

130

250

500

EXCE

BUTYL

85

105

220

500

V.G.

PVC

70

95

160

700

POOR

MECHANICAL & ELECTRICAL PROPERTIES.

TENSILE

ELOGNATION

ABRATION

DI-ELECT

TAN δ

VOL



















Cable and Insulator

MISCELLANEOUS PROPERTIES :

WATER RES

CORONA RES

CHEMICAL FLEME RES RES

ABRATION

XLPE

V.GOOD

POOR

GOOD

POOR

GOOD

PE

EXC

POOR

GOOD

POOR

GOOD

EPR

GOOD

GOOD

FAIR

POOR

POOR

BUTYLE

GOOD

FAIR

FAIR

POOR

POOR

PVC

FAIR

GOOD

GOOD

EXC

GOOD

SEMI CONDUCTOR

Conductor is made up of several wires of smaller diameters. As the electric stress is increased with reduced diameter, a semi con layer is



















Cable and Insulator

TYPE OF SEMICON SHEILDING

∆

Stripable

∆

Easily Stripable

SHEATHING

Over all insulation over core is called sheath. In paper cable lead or lead alloy sheath are used to protect insulation from moisture.

ARMOURING

Applied over a bedding, this protects the cable from mechanical damage and act as return path for fault current.



















Cable and Insulator

SERVING

The external wrapping on the outer part of the cable is called serving. Serving protects the cable against corrosion and mechanical damage. It also protect the cable from chemical’s, corrosion soil, moisture etc. Serving is made up of tape made of combination of paper, jute, cotton, cloth etc. saturated with bituminous compound. TYPE OF DESIGNATION

A

Aluminum Conductor when type Designation Does not contain “A” in the beginning, cable is with copper conductor.

Y

When first or second place in type designation, it stands for PVC insulation

CE

Individual core screening



















Cable and Insulator

EXAMPLE :- AYFY 3x 400 sm 650/1100V

Aluminium Conductor, PVC insulated, Flat Steel Strip Armored, PVC overall sheathed 3 core, 400 sq mm stranded sector shape 650/1100 V Grade. EXAMPLE :- YY 37 X 1.5 re 650/1100 V



















Cable and Insulator

SELECTION OF CABLE Following parameters needs to be considered 1.

Type Type of insulation PVC, XLPE, PAPER ETC Table

shows

comparision

of

properties

of

insulating

materials used for low tension cables PROPERTIES

XLPE

PAPER

PVC

1. Operation Temp.

90

65

70

2. EM. O/L Temp c. .

130

100

120

°





















Cable and Insulator

TYPE OF CONDUCTOR TYPE OF ARMOURING NO. OF CORE VOTAGE GRADE

THE GRADING A RE NORMALLY 650, 1.1KV, 11KV, 11KV, 33KV, 33KV, 132 KV



















Cable and Insulator

Tisco standard 02040/2 Multi core armored power cable with stranded conductors confirming to IS : 1554 – 1988 Recommended Current Rating Sl.No.

Cross section

No. of

Laid in

Laid in

Laid in

Area

Core

Ground

Duct

air

1

4

3

28

23

23

2

6

3

35

30

30

3

10

2

55

45

47



















Cable and Insulator

Recommended Current Rating Sl.No.

Cross section

No. of

Laid in

Laid in

Laid in

Area

Core

Ground

Duct

air

19

120

3½

185

155

180

20

150

3

210

175

205

21

150

3½

210

175

205

22

185

3

235

200

240

23

185

3½

235

200

240



















Cable and Insulator

TABLE TABLE – 2

Cable laid on racks/trays in covered trench where air circulation is retracted,

trefoils

are

separated

by

twice

the

cable

diameter

horizontally and trays in tiers with 300mm gap between them. Ground rating factor

No. of Racks Trays in tiers

No. of trefoil in horizontal formation

1

1

2

3

2

0.9

0.85

0.83



















Cable and Insulator

TABLE –4 Cable laid in racks/Trays expose to air. The cable touches each other and racks/trays in tiers spaced by 100 mm spaced between wall and cable is 25 mm No. of Racks

Group rating Factor

Tray in Tiers

1

1

2

3

4

5

1.00

0.48

0.80

0.75

0.73





















Cable and Insulator

SELECTION OF CABLE FOR GENERAL PORPOSE CABLE

The required current rating is computed by dividing the current rating



















Cable and Insulator

The actual requirement is computed by dividing current rating of the



















Cable and Insulator

TABLE TABLE – 7

AMBIENT CORRECTION



















Cable and Insulator

TABLE – 9 CORRECTION FOR THERMAL RESISTIVITY



















Cable and Insulator

VERLAY LOOP TEST





















































































































































































































Cable and Insulators

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