Installation & maintenance of power cable

By-Ambuj Mishra

11/22/2013

LEAP Infraasys Pvt. Ltd.

1

1- SLECTION OF CABLE
A- Type of cables and their Application.
B- Selction and planing of cable installation.

General

Load condition

Installation condition

2- GENERAL
A- Guidelines for cable laying and installation.
B- Meathod of cables laying and installation.
-Laying direct in ground.
-Laying on racks in air.
- Laying cable on racks inside tunnel.

3- PACKING, TRANSPORT & STORAGE
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SLECTION OF CABLE
A-Type of cables and their Application:- A power
cable is an assembly of two or more electrical
conductors, usually held together with an overall
sheath.
Types:1-PILC Cables- Paper insulated lead covered cables
continue to be very popular where utility service is
required for underground electrical distribution
systems.

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2- PVC Cable- PVC Insulated power cable is
used to transmit and distribute power on the
power line.
3-XLPE cable- This type of Power Cable is used
for power transmission and distribution line.In
comparison with PVC Insulated Power Cable,
XLPE power cable is much better than.

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B- Selction and planing of cable installation.
 General-Which type cable are required and measuring
the Length of the cable rute.
 Rute indicators-Indicators should be provided at an
interval not exceeding 200m and also at turning points
of the power cable rute.
 Soil condition-The knowledge of the soil and
environmental condition helps in selecting type of finish
of protective covering of the cable and the rute of
laying.
 Nature of soil-The current carrying capacity of the cable
is dependent on the thermal resistivity of soil and
groung temperature.

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

Operating condition

A-System voltage- It’s a maximum operating voltage
whether DC or AC.
B-Earthing Condition- In 3-Phase system it is necessary to
know where the neutral points effectively earthed,or
earthed through resistance.
C-Load Condition-Actual load condition helps in choosing
correct cross-section of conductor for cable.
Load condition are as follows
Normal Load- Its means current w/b flowing
continuously through cable.

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





Intermittent load-If the cable is switch “on” and “off”
pariodically so the time b/w switch “off” and then “on” is not
sufficent to cool the conductor to the ambient temp.
Short time load-Under these load condition the conductor is
allowed to cool down to ambient temp.

Installation condition- Method of laying,installation

details such as thermal resistivity,soil resistivity dimension of
trench,number,type,cross section area and the load of all
power cable.
Basically difficulties expected during installation is1- Mechanical Stress
2- Vibration
3- Railway,road and river crossing.
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Guidelines for cable laying and installationA- Selction of route It is integrated part of the t/m and distribution system.

For transporting the cable drumps to work site ,it is
necessary to check the road condition ,in including
turns and width.
Specialy attention should be paid to the load bearing
capacity of the bridge.
 If possible cable should be laid along the footpath
rather than the carriage way,the route should be as far
as possible , away from parallel running gas,water
pipes & telecommunication cable.

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B- Minimum bending redius- Minimum bending
radius is the radius below which the cable
should not be bent..

Note-At the joint & termination bending redius for
the individual core should be above 12 times
the diameter over the insulation.
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Minimum recommended bending radius are given in
tableVOLTAGE RATING

PILC CABLES

PVC & XLPE CABLES

Single-Core

Multi-Core

Single-Core

Multi-Core

Up to 1.1 Kv

20D

15D

15D

12D

Above 1.1 to 11 Kv

20D

15D

15D

15D

Above 11 Kv

25D

20D

20D

15D

Note-D is outer diameter of cable

C- Maximum permissible tensile strength for cableTensile strength must be considered during the
installation process. It is the maximum stress that a
material can withstand while being pulled.

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Meathod of cables laying and installation
A-Laying direct in groung1- Laying of cable and bedding of minimum 75mm soil or
sand at the bottem of the trench and covering it with
additional soil or sand of minimum 75mm and protecting it
by means of tiles, bricks or slabs.
2- The disired minimum depth of laying from ground surface
to the top of cable is as followsHigh voltage cables.3.3kV to 11kV rating
: 0.9 m
High voltage cables.22kV to 33kV rating
: 1.05 m
Low voltage and control cables
: 0.75 m
Cables at road crossings
: 1.00 m
Cables at railwaycrossings
: 1.00 m

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3- The desired minimum clearance are as fallowsPower cable to control cables
: 0.2 m
Power cable to communication cables
: 0.3 m
Power cable to gas/water main
: 0.3 m
* The power cables should not be laid above the
telecommunication cable.
* For identification of power cables, the cable protective
cover,such as bricks or RCC slabs may be sutaible
marked by world “Power cable” .
4- Ducting blocks shouls be used where cables cross road
& railway tracks. Spare ducts for future extension should
be provided. The diameter of the pipe or duct should be at
least 1.5 times the outer diameter of the cable.


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B- Laying on racks in air1- Iside the buildings ,industrial plant,generating station
and substation cable are generally installed on racks
fixed to the wall or supported from ceilling.Rack may be
ladder or perforated type.
2- The vertical distance b/w the two racks should be
minmum 0.3 m and the clearance b/w the first cable
and the wall(if racks are mounted on wall)should be
25mm.
3- Cable laid on horizontal racks need be clamped at
suitable intervals.The distance b/w the vertical clamps
should not be more than 2 m.
- The arrangement of cable tray as shown is figer.
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C- Laying cable on racks inside tunnel. Inside
tunnel cable are generally installed on racks fixed
to the wall.
The arrangement
as shown in fig.

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PACKING, TRANSPORT & STORAGE
1- Cable are generally received wound on wooden
drump,both ends of the cable being easilly
acceasible for inspection and testing.
2- The cable drums not be dropped or thrown from
railway wagons or trucks during unloading
operations.A ramp or crane may be used for
unloading cable drums.
3- The arrows painted on the flange of the drum
indicate the direction in which the drum should
be rolled.
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4- The site chosen for storage of cable drums
should be well-drained and should preferably
have a concrets surface.
5- All drums should be stored in such manner as
to leave sufficient space b/w them for air
circulation.During storage, the drum should be
rolled to an angle of 90* once every three
months.

11/22/2013


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FOR YOUR
ATTENTION

11/22/2013


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Installation & maintenance of power cable

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