1.3 Machines:
There are six machines used for insulation: BM 80, BM 100, BM 120, BM 150, BM160 and SAM P BM 160. The number appeared in the name of the machine is related to the diameter of the screw of each machine. Section 3 of this report gives a wide overview of those machines and their specifications. Any machine is able to put insulation, but the BM150 and BM160 is mainly used for bedding and sheathing.
2. PROCESSES
2.1. Introduction
Three different processes are carried out in the insulation section
• insulation,
• bedding,
• Sheathing.
2.2. Insulation process
Two materials are used for the insulation process: Polyvinyl chloride (PVC), and cross-linked polyethylene (XLPE).
The main differences are summarized as follows
• PVC has a maximum operating temperature of 70 C, and for the XLPE is 90 C.
• XLPE, P.V.C are used as insulation for LV cables, while XLPE is used just for MV and HV. However, the incoming material of XLPE used in MV and HV is more pure than in LV, so it is stronger, but at the same time more expensive.
• PCV and XLPE are color less by nature. The color is put according to the customer needs and the Standards; the basic colors are: Red, yellow, blue, and black. The ratio of color is 2 % for PVC and between 0.5 % and 1 % for XLPE. The name of the material used for coloring is "Master batch".
2.3. 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 and to protect the insulated cores from the effect of the armoring or screening.
2.4. Sheathing process
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.
Materials used here are coming in colors, not natural or color less as for insulation.
PVC is used for LV and MV, and its color is according to the Standards (black, red, yellow, etc). The sheathing depends on the customer (depending on its use) and it can be divided as: Flame retardant, flame and termite retardant, acids retardant, ultraviolet retardant, L.S.O.H, underground water resistant.
PE comes in black color, and it is divided into three types, the first two used for MV, LDPE (Low Density PE) and MDPE (Medium Density PE), and the third one used for HV, HDPE (High density PE).
Thursday, February 3, 2011
Friday, January 28, 2011
power cable insulation section
1. Insulation section:
1.1 introductions:
- It is a process, for protecting the conductor from the contact with the other conductors in the cable (multi core cables), or due to any external hazards (single core cables).
- The insulation dielectric withstands the voltage applied on the cable during the testing or operating conditions.
- The insulation done by Extrusion process.
- The types of cables in this section of insulation:
1- Low voltage cables:
* Solids.
* stranded (round, compact, sector).
1.2 Materials:
Two types of insulation materials:
1- P.V.C Polyvinyl chloride:
Polyvinyl chloride (PVC) is a flexible or rigid material that is chemically non reactive. PVC has a broad range of applications, from high volume construction related products to simple electric wire insulation and coatings. Rigid PVC is easily machined, heat formed, welded, and even solvent cemented. PVC can also be machined using standard metal working tools and finished to close tolerances and finishes without great difficulty. PVC accepts paint and performs well under most silk-screening processes. PVC resins are normally mixed with other additives such as impact modifiers, fillers and stabilizers, providing hundreds of PVC based materials with a variety of engineering properties.
There are three broad Classifications for rigid PVC compounds: Type I, Type II, and CPVC. Type II varies from Type I due to greater impact values, but lower chemical resistance. CPVC has greater high temperature resistance. These materials are considered "un plasticized", because they are less flexible than the plasticized formulations. Type I, II and CPVC are normally available in rod, sheet, slab, pipe, tubular bar, fittings and valves. "Plasticized" PVC is available in sheet, film, fittings, flexible tubing, and pipe.
P.V.C Polyvinyl chloride (for cables):
- It is a compound material.
- Most used materials for the insulation of L.V cables.
- Max operating temperature: 70 degree.
- It is a flexible and flam retardant material.
- Profile temperature during process up to 175 degree.
- It is a thermoplastic material.
- Always provides in granules.
2- PE: Polyethylene:
-Polyethylene resin is useful for applications that require chemical resistance, little or no moisture absorption and flexibility. Its use is limited to temperature applications below 200 degrees Fahrenheit, and it has the ability to carry light loads for a long period. Polyethylene products include machined valves and fittings for fluid handling systems, tanks and pumps and industrial products that require a thermoplastic with low or high density, linear low density or ultra low density, tie-layer resins or adhesive resins. Polyethylene satisfies demands for reduced weight, increased strength, fast processing and lower costs. Polyethylene meets the needs of many tough applications.
-Three types: H.D.P.E, M.D.P.E, L.D.P.E
- H.D.P.E is mostly used in the insulation of communication , data and irrigation cables , due to its dielectric is constant and very low value so it decreases the capacitance of the pairs inside the cable , the surface is very smooth so they can not absorb the water , withstand high operating temperature.
-H.D.P.E also mostly used in the jacketing of M.V , H.V and EX H.V cables with black color to resist the ultraviolet sun beams .
- The profile temperature of the P.E during insulation process is up to 200 degree.
3 -XLPE (cross linked polyethylene):
Since cross linked polyethylene was introduced for the insulation of power cables in the 1960's, XLPE cables have became the industrial standard for voltages from 1kv to 150kv. Excellent technical properties, advantageous production economy and ease of installation and operation are the primary reasons for this development.
Step wise improvements in quality of insulation and semi conductive compounds, as well as cable production processes, have enabled stresses in the extruded dielectric to rise to a level which permits the safe design of cables for voltages up to 500kv.
- The X.L.P.E has high mechanical and thermal properties, operating temperature up to 90 degree,
It consists of two materials the main material which is L.D.P.E and a catalyst, to have the full mechanical and thermal properties of the insulation material the cross liking (curing) must be achieved between the P.E and the catalyst.
Cross linking (Curing) process:
1- mixing the L.D.P.E resin with 5 % catalyst and 1-2% master batch , and make the insulation process to produce an insulated cable , till now there is no X.linking or curing between the P.E resin and the catalyst so the insulation will fail in the Hot set test ( the test that insure that curing is done ) , we must make a heat treatment for the insulated cores , by putting the insulated cores in a heated steam Room named sauna in a temperature 90 degree for 8 hours , after that apply hot set test to ensure that the X. linking is occurs between the P.E resin and the catalyst and the insulated cores gain its thermal and mechanical properties of X.L.P.E material .
2- Current technology;
Now it is not need to use a Sauna or make heat treatment to the insulated cable with X.L.P.E
Due to the latest technology the catalyst is supplied to make self curing with the P.E resin during the insulation process or after 2 hrs, 24 hrs, 2 days according to the specification of the supplied catalyst.
Hot set test:
/ L original x100 Elongation = (L final –L original)
Types of curing technology
3- Benefits of cross linking:
- increased temperature performance.
- increased tensile strength.
- reduced deformation under load.
- improved chemical resistance.
- increase abrasion resistance.
4 –L.S.O.H (low smoke 0 halogen):
- It is a thermo set material, special type of X.L.P.E with free of smoke.
- Also supplied with resin and catalyst.
- used for insulation or sheathing for a special proposes, if the customer needs no smoking from the cable during the fire.
5- EPR: Ethylene Propylene Rubber.
- It is a very flexible material.
- used for insulation and sheathing for some mechanical proposes.
Sunday, May 23, 2010
Drawing
Drawing
5 - COURSE WIRE ( CW1, CW2, CW3, CW & CW5):-
5 - 1 Purpose:-
Objective of course wire machine is drawing Copper wire or Aluminum wire
from big diameter to small diameter.
Drawing Copper wire has diameter 8mm to many different diameter.
Drawing Aluminum wire has diameter 9 mm or 9.5 mm to many different
diameter.
If decrease in wire diameter then increase in speed of the machine.
If increase in final wire diameter then decrease in dies was used.
5 - 2 Advantage of drawing solution:-
1- Low temperature of mechanic tools.
2- Service life of die.
3- Quality of wire surface.
4- Cooling for die.
5- To making wire to slide inlet dies and capstans (pulleys).
6- Keep the color like sunshine.
5 - 3 How to operate Course Wire machine?
1- Put wire was drawing from upper diameter to different diameters in pointing machine.
2- Put the wire drawing inlet first die and does again steps 1 for second die tell final die (final diameter from final die).
3- Wire drawing passes the annealed and its advantage, the wire after drawing was became hardness and inlet in the annealed to become softness.
4- Take - up:-
a- It has tow spoolers (Tow bobbins).
b- Basket.
5 - 4 Shutdown of machine:-
1- Cut wire.
2- Friction in dies.
3- Friction in pulleys (capstans).
4- Shutdown in dancer.
5 - COURSE WIRE ( CW1, CW2, CW3, CW & CW5):-
5 - 1 Purpose:-
Objective of course wire machine is drawing Copper wire or Aluminum wire
from big diameter to small diameter.
Drawing Copper wire has diameter 8mm to many different diameter.
Drawing Aluminum wire has diameter 9 mm or 9.5 mm to many different
diameter.
If decrease in wire diameter then increase in speed of the machine.
If increase in final wire diameter then decrease in dies was used.
5 - 2 Advantage of drawing solution:-
1- Low temperature of mechanic tools.
2- Service life of die.
3- Quality of wire surface.
4- Cooling for die.
5- To making wire to slide inlet dies and capstans (pulleys).
6- Keep the color like sunshine.
5 - 3 How to operate Course Wire machine?
1- Put wire was drawing from upper diameter to different diameters in pointing machine.
2- Put the wire drawing inlet first die and does again steps 1 for second die tell final die (final diameter from final die).
3- Wire drawing passes the annealed and its advantage, the wire after drawing was became hardness and inlet in the annealed to become softness.
4- Take - up:-
a- It has tow spoolers (Tow bobbins).
b- Basket.
5 - 4 Shutdown of machine:-
1- Cut wire.
2- Friction in dies.
3- Friction in pulleys (capstans).
4- Shutdown in dancer.
CABLE CONSTRUCTION
4 – 3 CABLE CONSTRUCTION:
4 - 3 - 1 Conductor:
-plain copper or aluminum, stranded or solid, circular compacted or sector shaped, all in accordance with IEC 60228.
-no. of wires and wire diameter are adjusted to the specified resistance, so the specification allows the manufacturer to choose the no. and diameter of wires within limits to attain the required specified resistance.
-standard conductor sizes are:
0.5 0.75 1 1.5 2 2.5 4 6 10 16 25 35 50 70 95 120 150 185 240 300 400 500 630 800 1000 1200 1400 1600 2000 2500mm².
Form 0.5 to 2.5mm², are circular compressed conductors.
Form 4 to 35mm², are circular and can be compacted.
Form 50 to 300mm² can either be circular or circular compacted or sector-shaped.
Form 400 to 2000mm², are circular compacted conductors
**sector shaped conductors, mainly used for low voltage cables.
**circular compacted conductors are used for MEDIUM and HIGH VOLTAGE cables.
4 - 3 - 1 Conductor:
-plain copper or aluminum, stranded or solid, circular compacted or sector shaped, all in accordance with IEC 60228.
-no. of wires and wire diameter are adjusted to the specified resistance, so the specification allows the manufacturer to choose the no. and diameter of wires within limits to attain the required specified resistance.
-standard conductor sizes are:
0.5 0.75 1 1.5 2 2.5 4 6 10 16 25 35 50 70 95 120 150 185 240 300 400 500 630 800 1000 1200 1400 1600 2000 2500mm².
Form 0.5 to 2.5mm², are circular compressed conductors.
Form 4 to 35mm², are circular and can be compacted.
Form 50 to 300mm² can either be circular or circular compacted or sector-shaped.
Form 400 to 2000mm², are circular compacted conductors
**sector shaped conductors, mainly used for low voltage cables.
**circular compacted conductors are used for MEDIUM and HIGH VOLTAGE cables.
Classification of cables
Classification of cables:-
4 - 1Classification of cables: cables are usually classified according to the voltage for which they are manufactured accordingly they are classified as:
* Low voltage cables, up to and including 1000 volts.
* Medium voltage cables, starting 2000 volts up to and including 33kv.
* High voltage cables, above 33kv up to and including 150kv.
* Extra high voltage cables, 220kv, 400kv and 500kv.
4 - 2 Requirements for the cables: the followings are the necessary items required for the cables:
-the copper or aluminum conductor should be of correct size suitable for the cable to carry the specified load without overheating the cable, and giving voltage drop within the limits.
-the cores of the cable must have the proper insulation thickness to give high reliability and safety at the voltage for which it is designed.
-the cable must have a mechanical protection so as to withstand the worst conditions of laying and installations.
-all materials used in manufacturing the cable should be stable chemically and physically through out the cable life.
4 - 1Classification of cables: cables are usually classified according to the voltage for which they are manufactured accordingly they are classified as:
* Low voltage cables, up to and including 1000 volts.
* Medium voltage cables, starting 2000 volts up to and including 33kv.
* High voltage cables, above 33kv up to and including 150kv.
* Extra high voltage cables, 220kv, 400kv and 500kv.
4 - 2 Requirements for the cables: the followings are the necessary items required for the cables:
-the copper or aluminum conductor should be of correct size suitable for the cable to carry the specified load without overheating the cable, and giving voltage drop within the limits.
-the cores of the cable must have the proper insulation thickness to give high reliability and safety at the voltage for which it is designed.
-the cable must have a mechanical protection so as to withstand the worst conditions of laying and installations.
-all materials used in manufacturing the cable should be stable chemically and physically through out the cable life.
Factors affecting cable choice 2
1 - Factors affecting cable choice:
2 - 6 Resistivity: it is the resistance offered by the material to the flow of current per unit length, and expressed in ohm / cm².
3 - CONDUCTORS:
-any material supporting current flow is called conductor.
-material of a conductor should have many free electrons, and since metals contain the freest electrons, so metals are the best conductors.
-the common materials used as conductors are: COPPER and ALUMINIUM.
3 - 1 COPPER:
-it is used in cables as a conductor because of its low resistance.
-the common properties of copper as a conductor are:
*resistance of a wire of standard annealed copper, one meter long and of uniform mass section of 1mm² is 0.017241 ohm.
*constant mass temperature coefficient of resistance is 0.00393/cº
*the density is 8.89gm / cm³.
-the international electro-technical commission (IEC) established an international annealed copper standard (IACS) for the resistivity of annealed copper for which the conductivity is equal to 100%.
3 - 2 ALUMINIUM:
-it is commonly used as a conductor since 1945 due to its low cost, good electrical conductivity, good tensile strength, low density and excellent resistance to corrosion.
-it contains a minimum of 99.50% of pure aluminium with a controlled amount of impurities.
-it is usually treated by adding boron to remove titanium, vanadium and zirconium which are harmful to electrical conductivity.
2 - 6 Resistivity: it is the resistance offered by the material to the flow of current per unit length, and expressed in ohm / cm².
3 - CONDUCTORS:
-any material supporting current flow is called conductor.
-material of a conductor should have many free electrons, and since metals contain the freest electrons, so metals are the best conductors.
-the common materials used as conductors are: COPPER and ALUMINIUM.
3 - 1 COPPER:
-it is used in cables as a conductor because of its low resistance.
-the common properties of copper as a conductor are:
*resistance of a wire of standard annealed copper, one meter long and of uniform mass section of 1mm² is 0.017241 ohm.
*constant mass temperature coefficient of resistance is 0.00393/cº
*the density is 8.89gm / cm³.
-the international electro-technical commission (IEC) established an international annealed copper standard (IACS) for the resistivity of annealed copper for which the conductivity is equal to 100%.
3 - 2 ALUMINIUM:
-it is commonly used as a conductor since 1945 due to its low cost, good electrical conductivity, good tensile strength, low density and excellent resistance to corrosion.
-it contains a minimum of 99.50% of pure aluminium with a controlled amount of impurities.
-it is usually treated by adding boron to remove titanium, vanadium and zirconium which are harmful to electrical conductivity.
Factors affecting cable choice
1 - Factors affecting cable choice:
* Application and environment in which the cable will operate.
* Working voltage.
* Load current or max. Rated is current for continuous operation.
* Suitable voltage drop.
* Installation data, in pipes, underground, in air.
* Short circuit current, and time of release.
2 – DEFINITION:
2 - 1 Wire: it is a solid material (copper or aluminum) of certain uniform diameter and uniform cross section, having specified electrical resistance.
2 - 2 Conductor: it is bundle of wires stranded in a specified way and shape having a certain resistance to form a uniform pass-way for electric current. It can be circular or shaped (sect oral).
2 - 3 Core: it is a conductor insulated with a dielectric material (polyvinyl chloride, polyethylene, cross-linked polyethylene, rubber, cellular polyethylene).
2 - 4 Cable: A core or more of cores assembled together, to form single, or multi core cable, to serve in single phase or three phase system.
2 - 5 Resistance: all conductor materials resist the electric current flow. This resistance is directly proportion to the resistivity of conductor material and the conductor length, and inversely proportion to conductor cross-sectional area. It is expressed in “ohm/m”, and is given the symbol “r”
Resistance= resistivity x length / area.
* Application and environment in which the cable will operate.
* Working voltage.
* Load current or max. Rated is current for continuous operation.
* Suitable voltage drop.
* Installation data, in pipes, underground, in air.
* Short circuit current, and time of release.
2 – DEFINITION:
2 - 1 Wire: it is a solid material (copper or aluminum) of certain uniform diameter and uniform cross section, having specified electrical resistance.
2 - 2 Conductor: it is bundle of wires stranded in a specified way and shape having a certain resistance to form a uniform pass-way for electric current. It can be circular or shaped (sect oral).
2 - 3 Core: it is a conductor insulated with a dielectric material (polyvinyl chloride, polyethylene, cross-linked polyethylene, rubber, cellular polyethylene).
2 - 4 Cable: A core or more of cores assembled together, to form single, or multi core cable, to serve in single phase or three phase system.
2 - 5 Resistance: all conductor materials resist the electric current flow. This resistance is directly proportion to the resistivity of conductor material and the conductor length, and inversely proportion to conductor cross-sectional area. It is expressed in “ohm/m”, and is given the symbol “r”
Resistance= resistivity x length / area.
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