1. i
Acknowledgments
I would like to express my great appreciation to engineers and
workers that supports me during my practical training in “International
Cables Company”.
Many thanks to Dr.Mohammed Talaat El Mestekawi and Dr.Ahmed
Husain Mohamed Elsaid that supervised our practical training.
It was my great honor to join the institute and specially the
department of Mechatronics engineering.
Really I find no words to express my feeling toward them, and I did
not find a word better than:
Thank You
2. ii
Abstract
International Cables Company
Is one of the most advanced power cables manufacturing facilities in Egypt
and Middle East recently, is one of the main Egyptian players in production of
power and telecommunication cables. It was established in the year 1993 in
the 10th of Ramadan city by Mr. Mamdouh Khalaf, Spread on 48,000 sq.
meters, 520 employees.
In the year 2005, the company was affiliated to Group with whom we
are backed with the new technology and technical assistance.
With energy as the basis of its development, , the worldwide leader in
the cable industry, offers an extensive range of cables and cabling systems.
3. iii
List of contents
Acknowledgments..................................................................................................i
Abstract................................................................................................................. ii
List of contents..................................................................................................... iii
List of figures ....................................................................................................... vi
CHAPTER 1
INTRODUCTION ..................................................................................................1
1.1 Company .................................................................................................1
1.2 General Information .................................................................................2
1.3 Technical Information “Cable Construction”.............................................3
CHAPTER 2
THE RAW MATERIAL ..........................................................................................5
CHAPTER 3
WIRE DRAWING PROCESS................................................................................6
3.1 Definition..................................................................................................6
3.2 Process....................................................................................................6
3.3 Annealing Process...................................................................................7
3.4 Lubrication ...............................................................................................7
3.5 Drawing Machines Specifications ............................................................8
CHAPTER 4
STRANDING PROCESS ......................................................................................9
4.1 Define ......................................................................................................9
4.2 Theory Of Process...................................................................................9
CHAPTER 5
INSULATION ......................................................................................................12
5.1 Materials Of Insulation Process .............................................................12
5.2 Insulation Machines Components..........................................................13
5.3 Insulation Layers....................................................................................15
5.4 CV LINE.................................................................................................15
CHAPTER 6
SCREENING PROCESS ....................................................................................22
5. v
LOW VOLTAGE CABLES...................................................................................36
13.1 Operating Voltage..................................................................................36
13.2 Cable Construction ................................................................................36
CHAPTER 14
MEDIUM VOLTAGE CABLES ............................................................................38
14.1 Operating Voltage..................................................................................38
14.2 Cable Construction ................................................................................38
CHAPTER 15
HIGH VOLTAGE CABLES..................................................................................40
15.1 Operating Voltage..................................................................................40
15.2 Cable Construction ................................................................................40
Appendixes .........................................................................................................42
Reference ...........................................................................................................43
6. vi
List of figures
Figure 2:1 copper raw material .............................................................................5
Figure 2:2 Aluminum raw material ........................................................................5
Figure 3:1 wire drawing process ...........................................................................6
Figure 3:2 annealing process................................................................................7
Figure 4:1 stranding process ................................................................................9
Figure 4:2 table stranding layers...........................................................................9
Figure 4:3 stranding machine .............................................................................10
Figure 4:4 stranding............................................................................................10
Figure 4:5 shape of cable at the end...................................................................10
Figure 5:1 pay off machine .................................................................................13
Figure 5:2 Caterpillar ..........................................................................................14
Figure 5 :3 CV line ...............................................................................................16
Figure 5:4 Conductor joint...................................................................................16
Figure 5:5 Accumulator.......................................................................................17
Figure 5:7 cable three layers ..............................................................................19
Figure 5:8 diameter control................................... Error! Bookmark not defined.
Figure 5:9 X-ray device.......................................................................................20
Figure 5:10 heating machine ..............................................................................21
Figure 6:1 screening ...........................................................................................23
Figure 8:1 bedding process ................................................................................25
Figure 9:1 armouring process .............................................................................26
Figure 10:1sheathing process.............................................................................28
Figure 10:2 marker keyboard..............................................................................29
Figure 10:3 ultrasonic marker .............................................................................29
Figure 12:1 drum standing ..................................................................................33
Figure 12:2 drum handling ..................................................................................34
Figure 12:3 drum truck lifting ..............................................................................34
Figure 12:4 transporting drum.............................................................................34
Figure 13:1 low voltage cable .............................................................................37
Figure 14:1 medium voltage cable......................................................................39
Figure 15:1 high voltage cable............................................................................41
7. 1
CHAPTER 1
INTRODUCTION
1.1 Company
Location
Company Name: International Cables Company
Address: Third Industrial Zone A2
Tenth of Ramadan, El-Sharqiyah
Mission
We offer an extensive range of cables and cabling systems to raise industrial
productivity, improve business performance, enhance security, enrich the
quality of life, and assure long-term network reliability.
Vision:
To Continue as one of the worldwide leaders in the cable industry and we will
accomplish this by exceeding the expectations of our customers whom we
define as partners and fellow employees, by committing to our shared values
by achieving the highest levels of customer satisfaction, with extraordinary
emphasis on the creation of value. In this way we will ensure that our profit,
quality and growth goals are met.
Values :
Customer Satisfaction
High quality of products
Development and Continuous improvement
Training, Development, and Education for employees
Creativity, Responsibility, High performance and loyalty of employees
8. 2
1.2 General Information
Selecting power cable
The following factors are important when selecting a cable
Maximum operating voltage
Insulation level
Load to be carried
Magnitude and duration of possible short circuit current
Voltage drop
Way or installation ( underground direct buried ,ducts or in air
Nature of soil
Specifications and 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
Weight and dimensions
Weight and dimensions characteristics are approximate and deviations are due
to manufacturing tolerance
Jacket marking
Standards marking printed on outer jacket consisting of
Name of manufacturer. “ ICC Cables “
Type designation , size of conductors
Rated voltage
Year of manufacturing
Any special parts upon request.
9. 3
1.3 Technical Information “Cable Construction”
Conductors
The process for manufacturing conductors can be divided
mainly in three parts:
1) Raw material incoming.
2) Drawing process.
3) Stranding process.
According to IEC, the conductors are either circular, circular compacted or sector
shaped and consists of
Plain annealed copper or aluminum
Plain or metal coated copper
The IEC gives minimum number of wires with minimum and maximum wire
diameters and maximum D.C. resistance for each conductor cross section area
according to its formation
Insulating materials
a) Thermoplastics
Polyvinyl chloride (PVC) is used with cables has low rated voltages
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
Main properties of PVC and XLPE
10. 4
Screening
Screening of cores in single and multicore cables
a) Conductor screen
It consists of a layer of extruded semi conducting compound
It is used in XLPE insulated cables and above
b) Insulation screen
1. Nonmetallic layer of extruded semi conducting compound
It is used 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 metallic
screen are according to national regulations and standards. It is
applied on each core or over cores assembly
Assembly of cores, inner covering and fillers
Core 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 cables . Also,
for sector shaped cores the filler are used 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
Armouring
a) For single core cables
Aluminum tape armoring
Aluminum wire armoring
b) For multi core cables
Double steel tape armoring
Steel wires armoring
Outer sheath
It is consists of PVC compound for cables
11. 5
CHAPTER 2
2 THE RAW MATERIAL
There are three types of raw material used in the metal section: Copper,
aluminum, and aluminum alloy. Before entering into the drawing process, a
welding machine must join the different coils, therefore in this way it becomes a
nonstop process. We can have copper with all possible cross-sectional areas.
Figure 2:2 Aluminum raw material
Figure 2:1 copper raw
material
12. 6
CHAPTER 3
3 WIRE DRAWING PROCESS
Figure 3:1 wire drawing process
3.1 Definition
It is a metalworking process used to reduce the cross-section of a wire by pulling
the wire through a single, or series of, drawing die.
It's a mechanical process aimed at reducing the diameter of wire by tension force
by 17 – 33% of its original diameter.
3.2 Process
First, the conductor rod is fitted at the entry of the die unit. Then, by means of
number of disks turning with a constant angular velocity, dies placed in front of
every disk, the wire is reduced in cross section area according to the required
diameter. The disks wind the wire by drawing it, force it through the neighboring
die and move it to the next disk. Drawing process ends with the last disk, but the
wire coming out is not suitable for direct use as it has become harder after
stretching and thinning during the process.
13. 7
3.3 Annealing Process
The annealing unit on the line is used to soften
the wire again, making it suitable for cable
production process. This unit consists of two
conductive pulleys having an electrical potential.
The wire passing through them forms a short
circuit.
3.4 Lubrication
Lubrication in the drawing process is essential
for maintaining good surface finish and long die
life. The following are different methods of
lubrication.
Wet drawing:
The dies and wire or rod are completely
immersed in lubricant
Dry drawing:
The wire or rod passes through a container of lubricant which coats the surface
of the wire or rod
Metal coating:
The wire or rod is coated with a soft metal which acts as a solid lubricant
Ultrasonic vibration:
The dies and mandrels are vibrated, which helps to reduce forces and allow
larger reductions per pass.
Figure 3:2 annealing process
14. 8
3.5 Drawing Machines Specifications
The specifications for each different machine are described as follows:
Aluminum drawing machine Aluminum:-
- Inlet diameter (input - raw material): 9 mm
- Output diameter of the wire: 1.35 mm
Aluminum Alloy drawing machine
- Number of dies: 15
- Inlet diameter (input - raw material): 9.50 mm
- Output diameter of the wire: 1.35 mm
Copper Intermediate machine
- Inlet diameter (input - raw material): 2.60 mm
- Output diameter of the wire: 0.60 mm
15. 9
CHAPTER 4
4 STRANDING PROCESS
Figure 4:1 stranding process
4.1 Define
Stranding is the process of forming the conductor, current carrying component
of the cable. A certain number of thinned wires are loaded to the stranding
machine. Number of wires is dependent to the conductor cross section and
currently used numbers are shown in below table.
Figure 4:2 table stranding layers
4.2 Theory Of Process.
The need of making the stranding operation can be explained as follows.
The current flows typically along the surface of the conductor, so to allow
the conductor to carry more current, more wires of smaller cross-sectional
areas are used instead of using just one of larger area. In this way,
conductors are made of layers of wires.
The operation of stranding can be summarized as follows. One wire is
placed in the center of the conductor; a second layer containing six wires
16. 10
is stranded around it, then becoming the "one + six" conductor the center
of the next third layer, which is made of a total of twelve wires; if the
conductor needs to have another layer, the previous "one + six + twelve"
becomes the center of the this new fourth layer.
Figure 4:3 stranding machine
Each new layer needs to be rounded to the previous one to avoid the
separation of the wires. The direction of each new layer is opposite to the
previous one For Sector conductors; the last layer is always made to the
left direction, while for round and round compacted is to the right. The goal
of this operation is to make the conductor resistant to any bending.
Figure 4:5 shape of cable at the
end
Figure 4:4 stranding
17. 11
Three types of conductors can be stranded during
this process:
a) Round (circular)
b) Round compacted
c) Sector compacted
Lay length
Lay length = D final conductor x Factor
This factor is determined by the number of wires of the conductor.
Conductor Factor
91 wires 8 – 10
61 wires 10 – 12
37 wires 12 – 14
19 wires 14 – 16
7 wires 16 – 18
Types of conductors produced after stranding
process:
1-ACC: All Copper Conductors
2-AAC: All Aluminum Conductors
3-AAAC: All Aluminum Alloy Conductors
4-ACSR: Aluminum Conductor Steel Reinforced
18. 12
CHAPTER 5
5 INSULATION
There are two areas of the production section related to insulation: The insulation
area with focus mainly in Low Voltage (LV) cables, and the CV line with focus in
Medium (MV) and High Voltage (HV) cables.
5.1 Materials Of Insulation Process
a) Polyvinyl chloride (PVC),
b) Cross Linking polyethylene (XLPE).
The main differences are summarized as follows:-
PVC XLPE
Cost Cheaper than XLPE More Expensive than PVC
Made in Egypt Imported
Recycling Yes No
Operating
Temperature
70°C 90°C
Short circuit
Temperature
160°C 250°C
Density From 1.4 to 1.6 g/cm3 0.92 g/cm3
Cooling trough
The conductor pass cool
water 14°C in cooling
system
Must be pass in hot water
60°C to 10m from cooling
system
Properties of cable insulation
1- Must have specific resistance.
2- Must be high dielectric strength (KV/mm)
3- Rigid and flexible.
4- Must be nonflammable.
19. 13
5.2 Insulation Machines Components
The main components of each insulation machine can be
summarized as follows:
Pay off.
Typically there are two units, one of them is working while the other one is
waiting until the first one finishes, therefore allowing a nonstop process.
This installed above the reels. Operation is carried out by means of two
accumulators
Figure 5:1 pay off machine
20. 14
Caterpillar.
It is used basically to pull the cable. The two caterpillars, one at the beginning of
the machine and the other one at the end, must work at the same speed.
Figure 5:2 Caterpillar
Head of the machine.
It is used to heat the insulation material, PVC or XLPE, before going to the head
of the machine. The extrusion method is used to melt this material.
PLC Control
To control the head, the line speed, etc.
Cooler
Once the cable is insulated, it is necessary to cool it before going into the reel.
Take up.
From here, the reel is ready to go to the assembly process. The tension of the
cable is controlled in the take up process.
21. 15
5.3 Insulation Layers
a) Semiconductor material
b) Insulation
c) Semiconductor material
That will be explained in the following
Semiconducting screens (sometimes called semicons or semiconducting
shields) are extruded over the conductor and the insulation outer surface to
maintain a uniformly divergent electric field, and to contain the electric field
within the cable core. These materials contain specially engineered grades of
carbon black to attain the correct level of stable conductivity for the cable
semicon or screens. Semiconducting screening materials are based on carbon
black (manufactured by the complete and controlled combustion of
hydrocarbons) that is dispersed within a polymer matrix. The concentration of
carbon black needs to be sufficiently high to ensure an adequate and consistent
conductivity. The incorporation must be optimized to provide a smooth interface
between the conducting and insulating portions of the cable. The smooth surface
is important as it decreases the occurrence of regions of high electrical stress. To
provide the correct balance of these properties, it is essential that both the
carbon black and polymer matrix be well engineered.
This is called C.V. lines
5.4 C.V. Line
Introduction:
The Continuous Vulcanization Line (C.V. Line) is a special case in insulation for
the Production Department. The objective here is to assemble multi core cables
for Medium Voltage, High Voltage with insulation machine of cross-linked
polyethylene (XLPE).
The main factor to decide which type of C.V. Line use is the curing process.
During this operation, the cable cannot touch any surface because of the high
temperature applied, the insulation is not solid at that time, it is almost melted,
and therefore, if the insulation touches any part of the heating tubs there would
appear faults in the insulation.
22. 16
There are three possible types of C.V. Lines depending on the position of the
cable
Vertical.
Horizontal.
Figure5:3CV line
All these three systems allow the cable to be exactly placed in the center of the
large tub. The vertical configuration is the best one, but it is very expensive and it
is also necessary to use a very high structure to contain the complete C.V. Line.
Centenary C.V. Line consist of
PAY OFF
There are two drums to carry out a nonstop process, one of them is running
and the other one is standing by until the first one finishes. At that moment,
the connection between conductors is made by means of a join, as shown in
Figure 18 the first layer of the two conductors is removed, the tub connecting
the two parts is added, and finally hydraulic compression is applied to make
the proper joint.
Figure 5:4 Conductor joint
23. 17
ACCUMULATOR
The accumulator has two pulleys that allow rounding the conductor between
them five times, with a total length of 250 m, with a distance of 50 m between
pulleys. In this way, the conductor is running above the accumulator while
doing the joint operation between conductors below the accumulator, and
allowing in this way, a non-stop process while changing drums in the pay off.
While doing the joint operation, the left pulley moves to the right pulley
allowing the accumulated cable to continue the process, once the joint is
finished, the left pulley goes back again.
CATERPILLARS
There are a few caterpillars along the C.V. line. Their main function is to pull
the cable and maintain at a proper tension. And to ensure that the cable is
completely centered in the head, heating zones tube and cooling tubes to
ensure that cable does not touch any surface along the line especially in the
triple head and heating zones.
Figure 5:5 Accumulator
24. 18
PRE-HEATER
It is not a fundamental machine for the process, however, it is considered to
be as a very important accessory. It has two main uses:
a) To allow the semi-conductor be correctly attached to the surface of the
conductor. The inner semi-conductor is hot and the conductor is cold, so
those differences in temperature make the layer of material not to
distribute properly along the conductor.
There are two possible solutions
b) To decrease the line speed allowing the material having more time to be
attached properly, although in this case the production can decrease
considerably, or using a pre-heater, and maintain the same speed.
c) The temperature of the cable after passing the cross head is not equally
distributed.
There are again two possible solutions:
To decrease the line speed to allow having more time for heating and
curing, or using a pre-heater for a better distribution of the temperature
along the diameter of the cable, allowing the first layers of the insulation
receiving heat from the center to cure properly the XLPE.
TRIPLE HEAD
It is also called Cross head. There are three extrusions machines to place the
insulation of the cable: One for injecting the inner semi-conductor, another one
for the insulation, and the final one for the outer semi-conductor. The head of the
machine is triple because there are three extrusions, the temperature inside is
around 120 C. The diameter of each one of the three layers placed from each of
the extrusion machines is controlled by an x-ray device .operation of injecting the
insulation is the same as that one carried out with the insulation machines.
25. 19
Figure 5:6 Triple head
There are 3 Extruders, for 3 layers of insulation:
1. For inner semiconductor layer.
2. For the X.L.P.E insulation layer.
3. For the outer semiconductor layer.
Figure 5:7 cable three layers
26. 20
X-Ray device
It makes photographs of the cross-
sectional area of the cable to measure
the diameters of the insulation in all
directions.
It is a positioner device that can be found
in the middle of the heating tub. It checks
if the insulation of the cable (three layers)
is in the center of the tube, while
producing a magnetic field that generates
a signal sent to the caterpillars to correct
the position of the cable if necessary. It is
not a basic device, it is just an accessory,
but it is better to use it.
It is used to measure the diameter of the
cable in cold.
Figure 5:8 X-ray device
27. 21
HEATING ZONE
The heating tub is divided in eight zones. The curing process is taken place
along this long tub. The temperature gradually decreases from the first zone
at 450 C (it is important to notice that inside the tub the temperature is around
290 C) to the eighth zone at 350 C - 340 C (depending on the cable voltage,
the line speed, etc.). After the eighth zones, the XLPE is cured; however it is
still very hot. The cable remains in the center of this tub without touching any
surface along this heating zone.
Figure 5:9 heating machine
NUL ZONE
No heating is applied to this zone. Without this zone, if the hot cable touches
the water it produces steam that goes up into the heating zone producing
some damage. For that reason, a cooling jacket is installed around the
external surface of the tub, and its function is to decrease the temperature of
the cable a little bit before entering in the cooling area.
COOLING ZONE
The objective here is to cool the cable after leaving the heating zone.
TAKE UP
Like in the pay off, there are two drums to allow a non-stop process.
28. 22
CHAPTER 6
6 SCREENING PROCESS
6.1 Definition
Screening is the
implementation of metallic
wires in such a number and
with such a diameter that is
able to withstand the short
circuit current. The short
circuit current depends on
the cable type.
6.2 Explanation
LV cables carry typically three phases and one neutral. However, MV (multi core)
and HV (single core) cables carry just three phases, being necessary to have an
"extra" neutral to carry the fault current, short circuit current, etc. this is done by
means of the screening.
Customers determine the quantity of screening being used by specifying the
weight of screening per meter of cable or also by giving the cross-sectional area
of screening. As a result of this, it needs to be determined the type of material
used for screening Copper wire or copper tape, being necessary to specify the
diameter in case of using copper wire, or the over lapping in case of using tape.
The maximum overlap is 48 % with higher percentages it is necessary to use
copper wire instead of copper tape, with the same technique as the one used for
armoring.
29. 23
Figure 6:1 screening
Two main benefits of using copper tape are:
(a) Possibility of deviating the current (electric field) far away from the point
where an existing insulation problem may appear (impurities, etc.).
(b) Possibility of having the earthling for the cable. The main benefit of using
copper wire is to earth the cable.
In the case of using copper wire, a new technique is being carried out to avoid
using copper tape: To decrease the diameter of the wire and increase the
number of wires. However, some customers still prefer to use copper tape to
ensure the connection.
30. 24
CHAPTER 7
7 ASSEMBLY PROCESS
7.1 Define
As said before the main function of this stage to put in one cables all phases
together,and covers them with propylene tape.
During this first step all conductors are assembled together in one cable and after
that the cable is covered with polypropylene tape
Any kind of cable can be assembled in this step.
7.2 Machine Parts
The assembly head
Contains the Screw axis and two Die holders. The first die has a diameter equal
to the diameter of the cable with an extra 2 or 3 mm (this value depends on the
diameter of the cable, for low diameters use 2 mm of tolerance), and it fixes the
cable to avoid movement during the entire assembly operation, the second die
has a suitable diameter with no tolerance to compact the cable, and to make it as
much rounded as possible.
The polypropylene filler
Fills the spaces between phases, allowing the cable to be round.
Cage with propylene tape device
1) To put one tape with a % of overlap
2) To put two tapes at the same time, with overlap between them,
31. 25
CHAPTER 8
8 BEDDING PROCESS
This process is done right after the assembly process. It is an operation done
between stages, before armoring, and before sheathing, if any of those two
operations are carried out
PVC is used as a material, but it is not the same kind of PVC used for insulation.
Now, it is recycled PVC of black color. It has not as good electrical characteristics
as that one used for insulation, however now there is no need of that, because
the objective of the bed layer of the cable is just to be a separator.
Figure 8:1 bedding process
32. 26
CHAPTER 9
9 ARMOURING PROCESS
Figure 9:1 armouring process
9.1 Definition
The armoring stage is carried out to protect the cable against any mechanical
stresses like for example ground pressure appeared over the underground cable
when a big truck is passing over generating a force through the soil that may
reach the cable.
Cables can use different types of armoring depending on the number of phases
The operation is carried out by
covering all the surface
area of the cable with wire.
33. 27
9.2 Armoring Single Core Cables
Single core means that it has single phase
Use armoring with aluminum wire or tape to avoid the magnetism generated in
the armoring material because of the magnetic field, found around the conductor,
creating by the current circulating in normal operation.
9.3 Multi Core Cables
Multi core means that it needs more than one phase may be two or three
Use armoring with steel wire or tape to avoid the mechanical stress happen on
the cable during using in the required position.
9.4 Types Of Armouring
a) Normal armouring
Although more expensive, is used to protect the armoring against corrosions.
This type of armoring is carried out basically to protect the cable against any
horizontal mechanical stresses as explained before
b) Steel wire armoring (galvanized)
This type of armoring is carried out to protect the cable against strains, i.e.
horizontal tensions appeared along the cable.
.
34. 28
CHAPTER 10
10 SHEATHING PROCESS
Figure 10:1sheathing process
10.1 Definition
The sheath is the outer jacket of a cable used as a cover, just for protection. This
process uses the same extrusion method as that one used for insulation and
bedding.
It is the last stage of cable manufacturing process.
10.2 Process
Cable, after its placement in the pay-off, is drawn through the cross head
connected to the extruder by means of caterpillars placed at both ends of the
line. Cable is sheathed with PE or PVC as it passes through the cross head and
enters the cooling channel right after embossing, marking and metering.
PE laminated aluminum tape can also be sheathed for radial water sealing during
outer sheathing by means of an apparatus placed near the cross head entry.
Outer sheath thickness is obtained by adjustment of synchronized extruder cycle
and line speed. Cooled cable is then dried then passed through marker printing
then wound to the reel on the take-up following the caterpillar and thus
manufacturing process is completed.
35. 29
10.3 Marker Printing
It prints the following without touching the cable using ultrasonic marker
Name of manufacturer. “ ICC Cables “
Type designation , size of conductors
Rated voltage
Year of manufacturing
Figure 10:3 ultrasonic marker
Figure 10:2 marker keyboard
36. 30
CHAPTER 11
11 TESTS AND QUALITY CONTROL
11.1 INTRODUCTION
Power cables can be divided according to the voltage:
1. Low Voltage, up to 1kV
2. Medium Voltage, from 1 kV to 36 kV
3. High Voltage, from 36 kV to 170 kV
Transmission of energy is done at high voltages and low currents to decrease
losses. Voltage is generated in a power station, an immediately is stepped up to
higher voltages by means of a transformer.
The tests carried out is electrical tests and mechanical tests.
11.2 TESTS CLASSIFICATION
A cable is considered to be made of insulated cores, and each different core is
made of a conductor with its insulation. The insulation is the most important
electrical layer when manufacturing cables.
Tests are made in this facility to verify some properties of conductors and
insulations, in order to carry out a preventive maintenance of the material.
Tests can be classified in the next way:
Destructive:
Flammability test: Period of burning after removal of the flame shall not
exceed 60 sec. And the unaffected portion from the lower edge of the top
clamp shall be at least 50 mm.
Non destructible
It is done over the entire product, which does not suffer or is damaged.
Typical electrical and mechanical tests are considered here.
37. 31
Sample tests:
A sample is taken from each different part of the manufacturing cable
process. These kinds of tests begin at the starting point of the production. If
the product passes the specific test then it can continue to the next stage of
the process. The goal is to measure if the product in each step accomplishes
the customer requirements.
Routine tests:
They are made upon 100 % of the product. These kind of tests always need
to be done.
11.3 ELECTRICAL TESTS
Low voltage cables
Two main requirements need to be accomplished in order to get a proper voltage
in buildings, factories, etc.
Voltage stability, which depends basically on the government.
Specified current, which depends on the cable.
It is very important to check two parameters with low voltage cables.
Dielectric strength of the material (insulation)
This test is carried out just one time, and no value is obtained, the result is just to
know whether the cable passes or not.
The test is made between conductors, and it is done in order to verify the
capacitive effect of the insulation.
38. 32
a) If there is a three-phase
transformer available, it will
allow directly to energize the
three conductors of the cable
(terminal one), maintaining
open the conductors in terminal
two, see Figure 1.
Electrical resistance of the conductor
If the value of the resistance increases, there will be also an increment in the
temperature of the cable, heating, and possibly over passing its melting point as
a consequence, therefore damaging the insulation.
Following the IEC 60228 Standard, the DC resistance at 20 C is measured. A
correction factor is used if the measurement is taken in other conditions of
temperature.
The value of the resistance varies depending on the frequency of the current
flowing.
11.4 MECHANICAL TESTS
The only one mechanical test carried out in this facility is the bending test.
The test is made by coiling and uncoiling four times the cable around the drum.
39. 33
CHAPTER 12
12 SAFETY
Safety and security procedures are form the most important things in the
workshop of any factory. But the major goal of safety systems is to preserve the
lives of workers inside workshop and outside (inventories, control rooms, etc.).
12.1 System Safety
1. Educate Engineers and technicians security and safety rules.
2. Training the people how to use the machines and other facilities in right
way.
3. Put safety plans and programs for how to transact with problems.
4. Using extension panels to warning workers.
12.2 Person Safety
Terms and conditions of clothes inside the workshop:-
1. Full coverage of all parts of the body.
2. Cloth used to be non-flammable.
3. Wear a shoe from certain ores.
4. The use of a helmet at all times while inside the workshop, but it is not
essential in our case
5. Use protective face and glasses during work.
6. Wear gloves.
12.3 Drum Handling Instructions
Figure 12:1 drum standing
41. 35
12.4 Additional Safety
Health hazards
When plastic is heated in the manufacturing process, fumes can be produced
which may severely irritate the lungs, eyes and nasal mucosa of anyone who is
exposed to them.
Fire prevention
Some of the materials used in the plastics industry are highly flammable and
present a fire hazard. Expandable polystyrene (EPS) bead, for example, contains
an extremely flammable gas that is given off from the material during storage or
transportation. Many factory fires have been caused by the accidental ignition of
leaking gas. Safety precautions around EPS bead includes not smoking
anywhere near where the substance is being stored or used. Heaters used
temporarily in winter should be checked because they pose a risk of igniting the
EPS bead.
42. 36
CHAPTER 13
13 LOW VOLTAGE CABLES
13.1 Operating Voltage
Up to 0.6/1 KV
13.2 Cable Construction
Conductor
Copper or aluminum conductors, solid, stranded or flexible with round or sectoral
shaped conductors
Insulation
An extruded layer of PVC or XLPE is applied over the conductor. PVC insulated
Cables are suitable for maximum conductor operating temperature of 70ºC or
85ºC and 90ºC for XLPE
Assembly
In case of multicore cables core are assembled together using non hygroscopic
filler to fill space between cores, wrapped with suitable binder tape to form a
round cable
Bedding
In case of armoured cables an extruded layer of PVC is applied as bedding.
Armouring
a) Steel tape
Double layers of steel tapes are applied helically
b) Steel wire
Galvanized steel wires are applied helically
43. 37
Sheath
An extruded layer of PVC is applied as an outer sheath or according to the client
special requirements
Options
Lead sheath upon request a layer of lead is extruded over the bedding
layer
Armouring by non-magnetic material either aluminum tape or aluminum
wire armouring to reduce magnetic losses.
Figure 13:1 low voltage cable
44. 38
CHAPTER 14
14 MEDIUM VOLTAGE CABLES
14.1 Operating Voltage
From 6/10 KV up to 18/30 KV
14.2 Cable Construction
Conductor
Round and compacted Copper or Aluminum conductors, according to IEC 60228.
Conductor Screen
An extruded layer of semi conducting material applied over the conductor as
voltage stress control layer.
Insulation
An extruded layer of cross linked polyethylene (XLPE) is applied over the inner
semi-conductor with thickness as specified in IEC
Insulation Screen
An extruded layer of strippable or firmly bonded to the insulation. Conductor
screen, XLPE insulation and insulation screen are applied at the same time using
triple head extruder.
Metallic Screen
a. Copper Tape
An annealed Copper tape is applied helically with a suitable overlap.
b. Copper Wire
Helically applied with a Copper tape to achieve electrical contact
45. 39
Assembly
In case of three core cables, cores are assembled together with suitable lay
length, non-hygroscopic filer is applied during assembly to fill spaces between
cores then wrapped with suitable binder tape.
Bedding
In case of armoured cables an extruded layer of PVC or MDPE or LLDPE is
applied as bedding.
Armouring
a) Steel tape
Double layer of tapes are applied helically.
b) Steel wire
Galvanized steel wires are applied helically.
Sheath
An extruded layer of PVC is applied with thickness as specified in IEC.
Upon request the sheath could be HDPE or LLDPE.
Options
Lead sheath upon request a layer of lead is extruded over the bedding
layer
Armouring by non-magnetic material either aluminum tape or aluminum
wire armouring to reduce magnetic losses.
Figure 14:1 medium voltage cable
46. 40
CHAPTER 15
15 HIGH VOLTAGE CABLES
15.1 Operating Voltage
Upper than18/30 KV
15.2 Cable Construction
Conductor
It consists of standard soft drawn copper or aluminum wires and classified into
two major types:
1. Compacted circular conductor
It consists of wires wounded up and then compacted.
2. Segmental compacted conductor
It consists of 5 segments and is applied for cross section over than 800
mm2 to improve A.C. resistance caused by skin effects.
Non-conductive water blocking tapes inside conductor for conductor
water and humidity protection are applicable upon request.
Conductor screen
It consists of an extruded thermoset semi conducting compound Semi conductive
tape with or without water blocking properties can be applied over the conductor
and under conductor screen.
Insulation
Insulated material of extruded XLPE applied over conductor screen.
Insulation screen
It is consists of an extruded thermosets semi conducting compound.
All the three layers (conductor screen + insulation + insulation screen) are
extruded simultaneously in one process to ensure that the screen and insulation
are firmly bonded together and free from all possibilities of voids between layers.
47. 41
Metallic screen
It is consists of copper or aluminum wires of lead alloy or sometimes the
combination of two materials to carry the required earth fault current with in the
required duration.
Outer jacket (outer sheath)
To Protect the metallic screen and the cable from surrounding mechanical or
chemical corrosion .It could be (LLDPE, MDPE, HDPE) or PVC material.
Semi conductive jacket
A semi conductive layer to be applied of extruded layer over the jacket layer for
jacket field testing after installation.
Figure 15:1 high voltage cable
48. 42
Appendixes
PVC : Polyvinyl Chloride
XLPE : Cross Linking Polyethylene
LV : Low Voltage
MV : Medium Voltage
HV : High Voltage
KV : Kilo Volt
IEC : International Electro-technical Commission's international
standard
ICC : International Cables Company
LLDPE : Linear low-Density Polyethylene
MDPE : Medium- Density Polyethylene
HDPE : High-Density Polyethylene
CV Lines : Continuous Vulcanization Line
IEE : Institution of Electrical Engineers
EPS : Expandable Polystyrene
