Icc Hv Cables

7/31/2019 Icc Hv Cables

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Quality Aspect:

International Cables Co. SAEPolicy is to supply customers with productsmeeting fully their stated needs. The products perform their required functions

safely, consistently and reliably for their intended use. They fully meet customer

requirements.

International Cables Co. SAE is affiliated to "Nexans Group" the world leader

in cables and cabling systems which support with the latest developments in the

field of materials and manufacturing methods.

International Cables Co. SAEsources its raw material from reputed suppliers.

Right from the beginning, all incoming material and cable constituents areanalyzed and tested to ensure their quality and compliance with specifications

before being processed. During manufacturing again complete tests are performed

on physical, mechanical and electrical properties of insulation and sheath

material.

Products have already been type tested from Extra High Voltage Labs.

Testing facilities are equipped with up-to-date most modern and advanced

laboratories as per international standards.

International Cables Co. SAEimplemented in its system total quality management.

Its commitment towards quality is reflected by achievement of ISO 9001:2000

(SGS certified).

Chairman

M. Mamdouh Khalaf


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Power CablesInternational Cables Co.

General Information

Selecting a power cable

The following factors are important when selecting a cable:

Maximum operating voltage

Insulation level

Load to be carried

Magnitude & duration of possible short-circuit current

Voltage drop

Way of installation

- Underground direct buried, ducts or in air

Nature of soil

Specifications & requirements to be met

If the ambient conditions are different than that given in our technical tables, it is recommended to modify

current rating by multiplying values in technical data tables by correction factors given in Section 4 .If flame propagation of fire is expected, it is recommended to have flame retarding materials or halogen free

materials for cable sheathing.

If chemicals (acids, alkaline) are expected in soil, we give special care for choice of PVC or PE or XLPE

materials, to resist this severe condition, when insulating or sheathing the cable.

If wet or muddy conditions in soil are expected, or cable will be submerged in water, water blocking tapes are

used for cables to prevent water penetration inside.

Voltage

The standard rated voltage of a cable is denoted by Uo / U (Um)

Where

Uo : is the rated power-frequency voltage between conductor & earth or metallic screen.U : is the rated power-frequency voltage between conductors.

Um: is the maximum continuously permissible operating voltage

Note: cable design for 6/10, 12/20, 18/30 kV is applicable for 6.35/11, 12.7/22 and 19/33 kV respectively.

Standards

Cables described in this catalogue are all standard types, and their performance has been proved in

operation.

Construction and tests are in accordance with the recommendation of IEC publications.

Power cables in accordance to other standards (e.g. BS, ASTM, VDE) can be produced upon request.

Weight and Dimension

Weight and dimension characteristics are approximate.

Deviations are due to manufacturing tolerance.

Jacket Marking

Standard Marking printed on outer jacket consisting of:

1- Name of manufacturer. ICC Cables

2- Type designation, size of conductor

3- Rated Voltage4- Year of manufacturing

5- Any special parts upon request

Uo/U (kV) 0.6/1 1.8/3 3.6/6 6/10 8.7/15 12/20 18/30 38/66 76/132 127/220Um 1.2 3.6 7.2 12 17.5 24 36 72.5 145 245


4/33

Power Cables International Cables Co.

Technical Information

Cable Construction

1 / Conductors:According to IEC 60228, the conductors are either circular, circular compacted or sector shaped

and consist of:

a) Plain annealed copper or aluminium class 1 or 2.

b) Plain or metal coated copper class 5 or 6 for flexible.

The IEC 60228 gives minimum number of wires with minimum and maximum wire diameters and maximum

D.C. resistance for each conductor cross sectional area (C.S.A.) according to its formation; if solid (class 1),

stranded (class 2), or flexible (class 5 or 6).

Comparison between copper and aluminium can be stated as follows

Properties Unit Copper Aluminium

Density g / Cm3 8.89 2.703

Resistivity Ohm. mm2 / km 17.241 28.264

Constant mass temperature coefficient 1 / C 0.00393 0.00403

Conductivity Siemens m/mm2 58 36

Temperature coefficient at C C 234.5 228

Specific heat per unit weight w / g / C 0.389 0.8870

Coefficient of linear expansion 1 / C 17 x 10-6 23 x 10-6

Ultimate tensile stress Kg /mm2 - 11.5 15.5

(annealed), approx. 25.0 -

(hard drawn), approx. 42.0 -

2 / Insulating Materials:

a) Thermoplastics:

Polyvinyl chloride (PVC) is used for cables with rated voltage Uo / U 1.8/3 kV.

b) Thermosetting:

Cross linked polyethylene (XLPE) is used for all kV ratings.

Thickness of insulation for each kind according to cable kV rating is indicated in IEC 60502


5/33


Main properties of insulation compounds are shown in the following table:

Properties UNIT XLPE PVC

Max. operating temperature C 90 70

Max. short circuit temperature C 250 160

Me

chanicalproperties

Without AgeingTensile strength N/mm2 min. 12.5 Min. 12.5

Elongation at break % min. 200 min. 120

After Ageing in

Air Oven

Ageing temperature C 135 100

Duration Hours 168 168

Tensile strength N/mm2 - min. 12.5

Variation % max. 25 max. 25

Elongation at break % min. 12.5Variation, max. % max. 25 max. 25

Physico-ch

emicalproperties

Ozone Resistance

- Concentration % - -

- Duration hours - -

Hot Set Test

- Ageing temperature C 200 -

- Duration under load (20 N/mm2) minutes 15 -

- Elongation under load % max. 175 -

- Permanent elongation after cooling % max. 15 -

Water Absorption:

Gravimetric method for 14 days at 85 C.

- Variation of mass g/cm2 max. 1 -

Resistance to

- Acids E E

- Alkaline E E

- Oil E E

- Heat distortion E F

Electricalprop

erties

Volume resistivity at 20 C . cm min. 1016 min. 1013

Volume resistivity at max. rated temperature . cm min. 1012 min. 1011

Dielectric power factor at ambient temperature:

* Tan at Uo X 10-4

max. 40 max. 1000

Dielectric constant:

* at rated temperature- 2.5 6 - 8

Insulation resistance Constant Ki:

*at 20 C M. Km - 367

* at max. rated temperature M. Km 3.67 0.037

E = excellent G = good F = fair


6/33


Comparison between XLPE and PVC insulation material

Properties UNIT XLPE PVCOperating temp.

(C)

Tan

XLPE PVC

Max permissible operating

temperatureC 90 70 20 0.00034 0.070

Max. permissible short

circuit

temperature

C 250 160 30 0.00035 0.085

Emergency

operating

temperature

C 130 110 40 0.00037 0.078

Dielectric loss

factor, tan 0.004 0.09 50 0.00039 0.063

Dielectric

constant, r

2.3 4.5 - 8 60 0.000042 0.057

Density g/cm3 0.92 1.45 70 0.00048 0.034

Volume resistivity . cm 1016 1014 80 0.00055 -

Thermal resistivity K.m/W 3.5 6 90 0.00062 -

3 / Screening:

Screening of cores in single and multi core cables, mainly for M.V cables:

a) Conductor screen:

It consists of a layer of extruded semi conducting compound.

It is used at rated voltages from 3.6/6 (7.2) kV in XLPE insulated cables and above.

b) Insulation Screen:

1 - Non metallic layer (applied upon the core insulation) of extruded semi conducting compound.

Insulation screen is used at rated voltages from 3.6/6 (7.2) KV in XLPE insulated cables and above.

2 - Metallic layer of one or more copper tapes or of copper wires where the dimensional, physical and electrical

requirements of the metallic screen are according to national regulations and standards. It is applied on each

core or over cores assembly.


7/33


Practical formula for metallic screen:

> Effective screen areaAeff:

where:

dM

= Mean diameter over screen.

t = Tape thickness.

4 / Assembly of cores, inner covering and fillers:Cores are laid-up to form a cable, where for circular cores polypropylene fillers are used to fill the interstices

between cores to get round shaped cable. Also, for sector shaped cores the fillers are used (if needed) to fill

the interstices if any to get circular shaped cable, then cable is wrapped with polyester tape for tightness. For

armored cables, a layer of extruded PVC is applied with a thickness according to IEC 60502.

5 / Armouring:

a) For single core cables:

Aluminum tape armoring (ATA)

Aluminum wire armoring (AWA).

b) For multi core cables:

Double steel tape armoring (DST).

Steel wires armoring (SWA).

The nominal diameters of round armour wires and nominal thickness of armour tapes are according to IEC

60502.

6 / Outer Sheath:

It consists of PVC compound for cables working at rated temperatures up to 70 C or PVC type ST2 for cables

of rated working temperature 90 C

We can use polyethylene (PE) or low smoke and halogen free sheath material where required.

100

2(100 - Overlap %)mm

2Aeff =. dM

. t.


8/33


Main properties of different types of covering and sheathing materials are shownin the following table:

Properties UNIT PVC PVC (ST2) PE

M

echanicalproperties

Without AgeingTensile strength N/mm2 min. 10 min. 12.5 min. 12.5

Elongation % min. 300 min. 150 min, 150

Ageing in air

oven

Temperature C 100 100 100

Duration hours 240 168 168

Tensile strength N/mm2 min. 10 max. 10 min. 12.5

Variation % max. 20 max. 20 max. 25

Elongation at break % min. 300 min. 250 min. 100

Variation % max. 20 max. 20 max. 20

Physical

properties

Pressure test at

high temp.

Duration hours - 4 6

Temperature C - 70 80

Variation % - max 50 max 50

Heat shock testDuration hours - 1 1

Temperature C - 150 150

Physico-chimicalproperties

- Flame propagation No Yes No

* Resistance to

* Humidity Good Excellent Good

* Chemicals Good Good Good

* Hydrocarbons Good Variable Good

* Ozone V. G. V. G. V. G.

* Weathering Good V. G. Good


9/33


1) Load Current:

a) For single phase, A.C. system I = P / V cos Ab) For three phases, A.C. system I = P / 3 V cos AWhere

P = Transmitted load in KW

V = Phase to phase voltage in KV

Cos = Power factor

2) Resistance:

Value of conductor D.C resistance given is based on

20 C. In case of any other temperature the following

formula is used:

R

= R20

[( 1 + 20

( - 20 )] /kmWhere

R

: Conductor D.C resistance at C /kmR

20: Conductor D.C. resistance at 20 C /km

: Operating temperature. C : Resistance temperature coefficient 1/C= 0.00393 for Copper

= 0.00403 for Aluminium

To compute AC resistance of the conductor at its

operating temperature the following formula is used:

RAC

= R

( 1 + ys

+ yp)

Where

ys

= Skin effect factor (to be calculated as per IEC 287).

yp

= Proximity effect factor

(to be calculated as per IEC 287).

3) Capacitance:

C = r/ (18 ln D/d) f/ km

Where

C : Operating Capacitance f/ km

r: Insulation dielectric constant

D : Diameter over insulation mm

d : Conductor diameter mm

4) Inductance:

Self and mutual inductance are indicated as below:

L = K + 0.2 ln(2S/d) mh/km

Where

L : Inductance mh/km

K : Constant depends on conductors number of wires

S : Axial spacing between cables in trefoil formation

S : 1.26 x axial spacing between cables in flat formation

5) Charging current:

The charging current is the capacitive current

which flows when AC voltage is applied to the

cables as a result of the capacitance between

the conductor & earth.

It can be derived form:

Ic = Uo

C 10-6 /kmWhere

Ic : Charging current A/km

Uo : Voltage between phase and earth Volt

: 2ff : Frequency Hz

C : Capacitance to neutral f/ km

6) Insulation Resistance:

R = K ln (D/d) M.kmWhere

R : Insulation resistance

K : Constant depends on the insulation

material

d: Diameter of conductor (including semi-

conducting material)

D : Diameter of insulated core

7) Dielectric Loss:

The dielectric losses of a cable are proportionalto the capacitance, frequency, phase voltage &

power factor.

D = 2 f C Uo tan 10-6 watt/km/phaseWhere

D : Dielectric loss watt/km/phase

f : Frequency Hz

C : Capacitance to neutral f/ kmtan : Dielectric power factor

Technical Data & Cable Parameters


10/33


Technical Data & Cable Parameters

8) Cable Ampacity:

Cable ampacity or current carrying capacity is

defined as the continuous maximum currentthe cable can carry at its maximum operating

temperature.

The following installation conditions were assumed

during current calculations:

Ambient air temperature = 40 C for L.V & 45Cfor M.V

Ground temperature = 30 C Ground thermal resistivity = 120 C.cm/watt Burial depth = 0.8 m- In case installation conditions are different than

above, derating factors must be taken in advance

- All calculations are based on IEC 60287

9) Cable short circuit capacity:

Short circuit starts from the maximum operatingconductor temperature

Maximum temperature during short circuitXLPE = 250 C

PVC = 160 C for C.S.A 300 mm2

PVC = 140 C for C.S.A > 300 mm2

Maximum short circuit duration is 5 seconds

It can be derived from

Is.c.t = Is.c.1 / t

WhereIs.c.t : Short circuit current for t second kA

Is.c.1: Short circuit current for 1 second kA

t : Duration Sec.

9) Voltage Drop:

When current flows in a cable conductor there is

a voltage drop between the ends of the conductorwhich is the product of the current and the

impedance.

It can be derived form:

For Single phase circuit:

Vd = 2 I (R cos + X sin ) Volt

For Three phase circuit:

Vd = 3 I (R cos + X sin ) VoltWhere

Vd : Voltage drop Volt

I : Load current Amp

R : AC resistance /kmX : Reactance /kmCos : Power factor : Length kmX = L 10-3 /kmL = inductance /kmCos = 0.8Sin = 0.6

For L.V cables, voltage drop should be calculated

so as not to exceed 3 to 5 % in normal operating

conditions.


11/33


Permissible short circuit current

of XLPE insulated power cables for 1-30 kV (Copper Conductor)

COPPER CONDUCTORS

Construction

Cond. max

temp. Normal

Operation

Short Circuit

Conductor

Max. Temp

Conductor Temp. at the beginning of short circuit

90 80 70 65 60 50 40 30 20

C C SHORT CIRCUIT CURRENT A./mm

XLPE Cable 90 250 143 149 154 157 159 165 170 176 181


12/33



of XLPE insulated power cables for 1-30 kV (Aluminium Conductor)

ALUMINIUM CONDUCTORS

Construction

Cond. max

temp. Normal

Operation

Short Circuit

Conductor

Max. Temp

Conductor Temp. at the beginning of short circuit

90 80 70 65 60 50 40 30 20

C C SHORT CIRCUIT CURRENT A./mm

XLPE Cable 90 250 94 98 102 104 105 109 113 116 120


13/33



for various cross section of round wire screens for M.V. Cables


14/33


15/33


16/33

highVoltage


38/66 (72.5) kV

Copper / XLPE / CUW / HDPE

C.S.ACond.

screenInsulation

Insulation

screen

Overall

Diam.Weight

Max. Cond.

ResistanceCapacitance

Current Rating

Ground Air

mm2 mm mm mm mm kg/kmDC at 20C

f / km

/km Amp. Amp. Amp. Amp.

240 R 1.0 11 1.2 59 5300 0.0754 0.164 487 459 647 640

300 R 1.0 11 1.2 61 6010 0.0601 0.176 547 482 736 724

400 R 1.0 11 1.2 64 6900 0.047 0.195 611 551 842 813

500 R 1.0 11 1.2 68 8000 0.0366 0.21 685 598 962 919

630 R 1.0 11 1.2 71 9335 0.0283 0.231 761 618 1097 1031

800 R 1.0 11 1.2 74 10600 0.0221 0.254 842 668 1238 1152

1000 S 1.0 11 1.2 82 13850 0.0176 0.282 967 712 1454 1316

1200 S 1.0 11 1.2 89 15765 0.0151 0.307 1036 744 1592 1420

Description

Stranded circular compacted or segmental conductor with copper material ,Semi-Conducting layer asconductor screen , XLPE insulation , Semi-Conducting layer as insulation screen, Semi-Conductive water

blocking tape , copper wire as metallic screen to achieve the required cross sectional area that carry the earth

fault current , non conductive water blocking tape to protect the metallic screen area from longitudinal water

penetration, double coated aluminum tape to protect the cable from radial water penetration and extruded

HDPE Sheath with semi-conducting extruded material.

Cables are designed and tested according to IEC 60228, 60840 and 60811.

> The Aluminium conductor can be manufactured upon request.

> The Insulation thickness can be processed upon request.

> The above dimensions can be processed upon request.

> The above data is approximate and subjected to manufacturing tolerance.

> The above data is calculated at 100% load factor.

> The current rating for above table was based on double end bonded (long distance).

R : Round

S : Segmental


17/33

high

Voltage


38/66 (72.5) kV

Copper / XLPE / LEAD / HDPE

C.S.ACond.

screenInsulation

Insulation

screen

Overall

Diam.Weight

Max. Cond.


Current Rating

Ground Air


f / km


240 R 1.0 11 1.2 61 9000 0.0754 0.164 495 503 659 660

300 R 1.0 11 1.2 82 10080 0.0601 0.176 556 533 751 749

400 R 1.0 11 1.2 64 11200 0.047 0.195 629 591 827 859

500 R 1.0 11 1.2 69 12315 0.0366 0.21 709 671 993 977

630 R 1.0 11 1.2 71 13470 0.0283 0.231 796 716 1138 1110

800 R 1.0 11 1.2 76 14120 0.0221 0.254 879 767 1285 1241

1000 S 1.0 11 1.2 81 18020 0.0176 0.282 1012 843 1513 1438

1200 S 1.0 11 1.2 88 19000 0.0151 0.307 1084 884 1654 1557

Description

Stranded circular compacted or segmental conductor with copper material, Semi-Conducting layer asconductor screen, XLPE insulation, Semi-Conducting layer as insulation screen, Semi-Conductive water

blocking tape to protect the metallic screen area from longitudinal water penetration, Lead sheath with

suitable thickness to achieve the required cross sectional area that carry the earth fault current and extruded


Cables are designed and tested according to 1EC 60228, 60840 and 60811.







R : Round

S : Segmental


18/33

highVoltage


76/132 (145) kV


C.S.ACond.

screenInsulation

Insulation

screen

Overall

Diam.Weight

Max. Cond.


Current Rating

Ground Air


f / km


400 R 1.2 16 1.5 62 8350 0.047 0.162 602 528 575 816

500 R 1.2 16 1.5 67 9420 0.0366 0.171 673 572 959 922

630 R 1.2 16 1.5 69 10895 0.0283 0.189 752 612 1096 1037

800 R 1.2 16 1.5 74 11175 0.0221 0.202 830 659 1237 1158

1000 S 1.2 16 1.5 79 14800 0.0176 0.223 956 708 1459 1332

1200 S 1.2 16 1.5 86 16705 0.0151 0.259 1022 742 1468 1438

Description


blocking tape, copper wire as metallic screen to achieve the required cross sectional area that carry the earth

fault current, non conductive water blocking tape to protect the metallic screen area from longitudinal water










R : Round

S : Segmental


19/33

high

Voltage


76/132 (145) kV


C.S.ACond.

screenInsulation

Insulation

screen

Overall

Diam.Weight

Max. Cond.


Current Rating

Ground Air


f / km


400 R 1.2 16 1.5 78 12350 0.047 0.162 617 581 858 851

500 R 1.2 16 1.5 81 13700 0.0366 0.171 695 636 983 967

630 R 1.2 16 1.5 85 14885 0.0283 0.189 780 697 1127 1101

800 R 1.2 16 1.5 89 15300 0.0221 0.202 865 754 1276 1235

1000 S 1.2 16 1.5 93 18980 0.0176 0.223 994 827 1502 1434

1200 S 1.2 16 1.5 97 20805 0.0151 0.259 1054 849 1634 1536

Description

Stranded circular compacted or segmental conductor with copper material, Semi Conducting layer as conductorscreen, XLPE insulation, Semi-Conducting layer as insulation screen, Semi-Conductive water blocking tape

to protect the metallic screen area from longitudinal water penetration, Lead sheath with suitable thickness to

achieve the required cross sectional area that carry the earth fault current and extruded with HDPE Sheath with

semi-conducting extruded material.








R : Round

S : Segmental


20/33

highVoltage


127/220 (245) kV


C.S.ACond.

screenInsulation

Insulation

screen

Overall

Diam.Weight

Max. Cond.


Current Rating

Ground Air


f / km

/Km Amp. Amp. Amp. Amp.

800 R 1.5 22 1.5 100 12600 0.0221 0.167 826 662 1230 1159

1000 S 1.5 22 1.5 105 16720 0.0176 0.186 949 709 1448 1334

1200 S 1.5 22 1.5 110 18800 0.0151 0.200 1014 739 1583 1441

Description


blocking tape, copper wire as metallic screen to achieve the required cross sectional area that carry the earth

fault current, non conductive water blocking tape to protect the metallic screen area from longitudinal water










R : Round

S : Segmental


21/33

high

Voltage


127/220 (245) kV


C.S.ACond.

screenInsulation

Insulation

screen

Overall

Diam.Weight

Max. Cond.


Current Rating

Ground Air


f / km


800 R 1.5 22 1.5 103 16900 0.0221 0.167 855 752 1269 1236

1000 S 1.5 22 1.5 108 20790 0.0176 0.186 983 825 1484 1424

1200 S 1.5 22 1.5 114 22830 0.0151 0.200 1066 868 1630 1548

Description

Stranded circular compacted or segmental conductor with copper material, Semi Conducting layer as conductorscreen, XLPE insulation, Semi-Conducting layer as insulation screen, Semi-Conductive water blocking tape

to protect the metallic screen area from longitudinal water penetration, Lead sheath with suitable thickness to

achieve the required cross sectional area that carry the earth fault current and extruded with HDPE Sheath with

semi-conducting extruded material.








R : Round

S : Segmental


22/33


23/33

explationn

otes

Power CablesInternational Cables Co. Power CablesInternational Cables Co.

Explanation notes

Current Carrying Capacities are based on the following conditions:

A) In Air:

Ambient temperature 45C (load factor = 0.8) where cables are protected from direct solar radiation.B) In Ground:

Soil temperature 30C, soil thermal resistivity 1.2 Km/W, and depth of laying 80 cm (load factor = 0.8).

C) Arrangement of the cables:

1 - Trefoil 3 cores laid in triangular shape.

2 - Flat 3 cores laid side by side.Clearance: in soil 7 cm.

in air 1 x cable diameter.

Note: Earthing of screens is on both ends

__________________

Rating Factor for Current Carrying

Capacity & Cable Installation

When laying or operating conditions differ than the normal one stated before, the following rating factors should

be used for calculating the current carrying capacity:

In Air

Ambient Temp. C 25 30 35 40 45 50 55

Factor 1.2 1.16 1.1 1.05 1.00 0.94 0.81

In Ground

a) Variation in soil temperature:

Soil Temp.C 25 30 35 40 45 50

Factor 1.05 1.00 0.96 0.91 0.87 0.82

b) Variation in soil thermal resistivity:

Soil Thermal Resistivity Km /KW 0.70 1.00 1.20 1.50 2.00

Factor 1.19 1.085 1.00 0.91 0.82

c) Variation in depth of laying:

Soil, Depth of Laying (m) 0.50 0.80 1.00 1.25 1.50 2.00

Factor 1.04 1.00 0.98 0.96 0.94 0.90

d) Factor for laying in ducts and pipes:

Cables in Ducts Bedding and filling with tamped sand and cover with bricks Factor = 1

Cables in Pipes Cable trough with cover, hollow space, air filled pipe Factor = 0.85


24/33

expla

tion

notes

Power Cables International Cables Co.Power Cables International Cables Co.

e) Factors for grounding in soil:

1 - Single core cables in 3-phase system:

Cable in Flat Formation (Clearance between System 7 cm)

Load Factor 0.8 1.0

Thermal Resistivity of Soil

Km / KW 0.7 1.0 1.2 1.5 2.0 0.7 2.0

N of Systems

in the trench

1 0.99 1.00 1.005 1.01 1.020 0.85

2 0.86 0.87 0.874 0.88 0.880 0.71

3 0.77 0.77 0.775 0.78 0.785 0.62

4 0.73 0.73 0.734 0.74 0.740 0.58

5 0.69 0.70 0.700 0.70 0.705 0.55

6 0.67 0.68 0.680 0.68 0.685 0.53

8 0.64 0.65 0.650 0.65 0.650 0.52

10 0.62 0.63 0.630 0.63 0.630 0.49

Cable in Trefoil Formation, Touching (Clearance between System 7 cm 25 cm)

Load Factor 0.8 1.0

Thermal Resistiv-

ity of Soil Km / KW0.7 1.0 1.2 1.5 2.0 0.7 2.0

Clearance be-

tween Systems

cm

7 25 7 25 7 25 7 25 7 25 7 25

N of Sys-

tems in the

trench

1 0.99 0.99 1.00 1.00 1.01 1.01 1.01 1.01 1.02 1.02 0.87 0.87

2 0.84 0.89 0.85 0.89 0.86 0.90 0.86 0.90 0.87 0.91 0.71 0,75

3 0.74 0.81 0.77 0.81 0.76 0.82 0.77 0.82 0.77 0.83 0.61 0.67

4 0.69 0.78 0.70 0.78 0.70 0.79 0.71 0.79 0.71 0.79 0.56 0.64

5 0.65 0.74 0.66 0.74 0.66 0.75 0.67 0.75 0.67 0.76 0.52 0.60

6 0.62 0.72 0.63 0.72 0.63 0.73 0.64 0.73 0.64 0.74 0.50 0.59

8 0.58 0.70 0.59 0.70 0.59 0.70 0.59 0.70 0.59 0.71 0.46 0.56

10 0.56 0.68 0.56 0.68 0.56 0.68 0.57 0.68 0.57 0.69 0.44 0.54

2 - Three core cables, all KV ratings:

Load Factor 0.8 1.0

Thermal Resistivity of Soil

Km / KW 0.7 1.0 1.2 1.5 2.0 0.7 2.0

N of Systems

in the trench

1 0.99 1.00 1.006 1.01 1.015 0.89

2 0.84 0.85 0.86 0.86 0.865 0.72

3 0.74 0.75 0.76 0.77 0.770 0.62

4 0.69 0.70 0.71 0.71 0.715 0.57

5 0.65 0.66 0.67 0.67 0.670 0.54

6 0.63 0.63 0.64 0.64 0.650 0.51

8 0.59 0.59 0.60 0.60 0.600 0.47

10 0.56 0.56 0.57 0.57 0.570 0.44


25/33

explationn

otes


Factors for laying and grouping in air

a) Grouping in air, single core cables in three phase system:


26/33

expla

tion

notes


b) Grouping in air, Multi-core cables in three phase system:


27/33

explationn

otes


CABLE PULLING, LAYING AND HANDLING INSTRUCTIONS

TABLE I - Installation Bending Radius for Low Voltage Cables

Type of Cable

Multiplying Factor

Installation bending radius

During Installation Fixed Installation

Single core (Un-armoured / Armoured)

Multi-core (Un-armoured / Steel Wire Ar-

moured)

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Multi-core (Steel Tape Armoured) 15 9

TABLE II - Installation Bending Radius for Medium Voltage Cables

Cable outermost sheath or coveringFactor to be multiplied by Overall diameter of cable


PVC 15 10

HDPE 20 15

Lead Sheathed (Un-Armoured) 18 12

Lead Sheathed Armoured 15 10

TABLE III - Installation Bending Radius for High Voltage Cables

Factor to be multiplied by Overall diameter of cable


25 25

TABLE IV - Permissible pulling force in the laying of LV, MV and HV cables

Means of pulling Type of Cable Formula Factor

With pulling head attached to the

conductorsAll types of cables P = . A

= 50 N/mm Copper

= 30 N/mm Alum.

With pulling stocking

Un-armoured Cables* P = . A = 50 N/mm Copper

= 30 N/mm Alum.

Armoured Cables** P = k. d k = 9 N/mm

Lead Sheath Cables P = k. d k = 3 N/mm

* When pulling 3 single core cables simultaneously with a common pulling stocking. the same maximum pulling force applies, whereas

the pulling force 3 laid-up single core cables is 3 times that of a single core and for 3 non-laid-up single core cables is 2 times that of a

single core.

** Not applicable for high voltage cables

P = Pull in Newton

A = Total cross sectional area in mm of all conductors (but not screen or concentric conductor)

d = Outside diameter of the cable in mm

= Permissible tensile stress of conductor in N/mm

k = Empirically derived factor in N/mm


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Earthing of Single Core H.V. and E.H.V. Cables

Distribution voltage cables are normally installed with solidly bonded sheaths and, in order to

minimize the sheath circulating currents on single-core cables produced by the magnetic flux linking

the conductors and sheaths, they are nearly always laid in close touching trefoil formation. However,

trefoil formation is poor for heat dissipation, as the three cables have a considerable heating effect

upon one another. This is generally not a limitation for cable system at 33 kV but with larger conductorsizes and higher voltages alternative specially bonded systems are more economic.

Special bonding involves earthing the single-core cable sheaths at one point only and insulating all

other points of the sheath from earth, so that the circulating sheath losses are eliminated and the

phase cables can design be spaced apart to reduce their mutual heating effect without increasing

sheath losses.

If one termination only is grounded, the sheaths are subjected to a standing voltage of zero at

the ground connection and maximum at the point furthest from this connection. This voltage is

proportional to the conductor current and cable spacing. To protect the sheath insulation against

transient voltages arising from lightning or switching transients it is therefore necessary to fit sheath

voltage limiters (SVLs) at all joint and sealing end positions where the sheath is insulated from

earth.

Three basic variations of specially bonded systems are commonly used: single end bonding, mid-

point bonding and cross-bonding.

Specially Bonded Cable Systems

Single End Bonding System

In this system the sheaths at one termination are earthed and at the other termination are insulated

from ground and fitted with SVLs. It is necessary to provide a separate earth continuity conductor for

fault currents which would normally return via the cable sheaths. The standing voltage is proportionalto the cabie length and therefore the voltage limitation imposes a limitation on the length of the cable

that may be bonded in this manner.

Mid-point Bonding System

Bonding of the mid-point is used where the route length is too long to employ a single end bonding

system. In this system the cable is earthed at the mid-point (at joint) of the route and is insulated from

ground and provided with SVLs at each termination or vice versa. It can be seen that this doubles the

possible route length as the maximum allowable standing voltage can be tolerated at each sealing

end or joint.

Cross-bonding System

In long routes, the route is split up into i:major sections, each comprised of three lengths and

special joints are fitted. At each third joint position the sheaths are connected together and at all

other positions they are connected so that all sheaths occupying the same position in the cable

trench are connected in series The sheaths at the intermediate positions are also connected to

SVLs. The three sheaths connected in series are associated with conductors of different phases and

when the cables are installed in trefoil formation their currents, and hence the sheath voltages, have

equal magnitude but phase displacements of 120. The overall effect if that the resultant voltage and

current in the three sheaths are zero. When cables are laid in flat formation the voltages induced in

the sheaths of the outer cable are greater than induced on the sheath of the middle cable and the

phasor sum is not zero. The cables are therefore transposed at every joint position and the cross-connections are made with a phase rotation opposite to that of transposition so that the sheaths are

effectively straight connected.


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explationn

otes


Drum Handling Instructions

Cables and Conductors should be installed by trained personnel in accordance with good engineering

practices, recognized codes of practice, statutory local requirements, IEE wiring regulations and

where relevant, in accordance with any specific instructions issued by the company Cables are often

supplied in heavy cable reels and handling these reels can constitute a safety hazard. In particular,

dangers may arise during the removal of steel binding straps and during the removal of retainingbattens and timbers which may expose projecting nails.


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Icc Hv Cables

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