Low Voltages Cable

OutlinesIntroduction.Components of the low voltage cables.Requirements that must be provided with

cables .Reserves Composition.Choosing cable.Tests performed on the low voltage cables.Conclusion.

IntroductionCable is a means of transportation and distribution of power generation areas to consumption areas as the overhead lines and other means of transportation.

Low voltage are voltages ranging from 100 to 1000volts.The purpose using cables is the transfer of energy in a proper way from the source to the devices to use, and during the process of energy transfer occurring phenomena such as high temperature cable as a result of loses as well as the voltage drop and the formation of electromagnetic fields on cable.

Components of the low voltage cablesManufactures cables either Single Core or

Three-Cores and perhaps more than that, and we can say in general that the use of cables triple cores leads to lower costs and reduce the voltage drop the cable signal core is more flexible and easier to install, plug and so the use of cables and a single heart be the best in commercial buildings due to the large exposure of the cable curves as well as the large number of branching and connections on the cable.

The cable single core consist of : 1 - conductor.2 - isolator.3 - cover .4 - external protection.

The cable triple core consists of: 1 - conductor.2 - isolator.3 - filler material .4 - linking Belt and Curtain Screen. 5 - Cover and external protection.

1. Heart ( conductor ) :The heart of the cable made from the material of high electrical

conductivity and using copper or aluminum in the manufacture of the connector cable and usually prefers to use copper connectors for some reason properties of electrical , mechanical and chemical best either aluminum conductors , they are also used extensively due to its cheap price and lightweight for copper connectors for the same current value . And in residential buildings and commercial establishments and administrative uses copper conductors Solid even sector (16) mm 2 on the most used and conductors scheduled for sectors up from that to get the flexibility.

2. Isolator Use of polymeric materials Polymeric Materials Industries now in all

the cables used in commercial buildings of different efforts and polymeric materials are materials derived from petrochemicals . Specifications to be provided in the insulating material

1 - high resistance. 2- flexibility. 3 - withstand high temperatures. 4- non-flammable. 5 - resistant to acidic.

3. Protection of Foreign Affairs :Using external protection or the outer shell to protect the

layers of the cable , which underneath of environmental conditions , installation and selected based material external protection on the same factors to choose the separation of any on the electrical properties and mechanical , physical and chemical also can provide cable protection metal or non-metal or a combination of both .

4. The metal cover :Require the specification of local and global supply cable

sheathed Shielding (Metallic Sheath if it exceeds the effort Cable certain limit (1 kV in accordance with the specifications of IEC-502) and made the cover of metal either of conductive material ( lead - alloy lead - aluminum alloy ) or a semiconductor material or both.

The casing is made of metal on different forms , including:1 - a strip of copper or steel.2 - corrugated copper bar is placed on the longitudinal separation

manner and prove by welding the upper damage to the copper wires of the separation in a spiral manner.

3 - Solid casing of lead are pasted along the separation by extrusion Extruded Lead Sheath..

It contains many kinds of cables on the internal metal casing is placed on or near the connector and metal casing that any external insulation be surrounded b tow casing from inside and outside

The metal casing has many advantages including ::1 - inventory of the electric field inside the cable.2 - provide a path for the current palace ground.3 - Reduce stress on electrical insulation, especially the areas in

contact with the surface of the separation, which caused the damaged

4 - Reduction of jamming communications devices.5 - To reduce the risk of electric shock in the case of a good

grounding for cable.6 - mechanical protection , chemical and natural material separation.

Requirements that must be provided with low voltage cables 1 - Quality of cable insulation to be safer. 2 - Strengthening the cable outside layer of

mechanical protection against external influences. 3 - fit the conductor with load. 4 - materials made from them with a degree

of cable high resistance to the effects of chemical and

physical.

Choosing cableChoosing of cables depends on several factors :1 - Load Properties : In terms of operating voltage and current load and ongoing

cycle of load and the extent of loading exceeded in periods of emergency and the time period allowed to go beyond the limits of load as well as the change in voltage.

2- Codified voltage: You must specify two values of the cables voltage : 1 - Operating voltage V a rated voltage between the connector

and the earth during normal operation2 - Vo effort insulation which is the maximum linear voltage

(line-to-line) can be borne by the cable when using cables in the system grounded.

3- Cross-sectional area of conductor : Choose the cross-sectional area of conductor, according to a number of factors

as follows: 1 - current-carrying capacity .2 - loading exceeded in periods of emergency .3 - the limits of the permissible voltage drop .5 - Terms of composition in terms of the method of installation and the

temperature of the connector cables and other neighboring .6 - Requirements connecting cable end.At first determine the cross-sectional area of conductor , according to the carrying

capacity of the current through the tables factory cables must then correct -sectional area of this depending on the installation conditions and they differ from standard conditions the corresponding tables , you must use transactions to reduce rationing Derating Factors as known in technical bulletins own cables so can select the area to the right section of the connector.

When choosing a cable we must know the amount of the decline in voltage between the two parties at the passage of the rated current in order to determine the amount of voltage regulation has traditionally been to give the landing caused by the passage of the current in the cable on the basis of each connector on the unit and is normally calculated in milliseconds volts per ampere per meter of cable length.

4- Method of installation :Cable can be buried directly in the ground or into streams can

also be placed on shelves or inside the pneumatic tubes In all these cases, you must know the space for the passage of the cables and the extent of convergence of some of them , especially if these cables are working on various efforts .

5 - The environment in which the pass-through cable :May pass the path of the cable areas with high temperatures ,

which requires special types of insulation may also pass the cable areas dangerous or prone to fires or explosions or contain chemicals incendiary or exposed to stresses high mechanical In such cases, you must choose the appropriate cable in terms of insulation and protection Foreign or mechanical reinforcement may be required in some cases, choosing cable high flexibility due to the curvature of the trajectory shows acute repetitive

Reserves CompositionThe process of installing the cable need to be special precautions to

avoid damaged1 - only be installed cables that enter the PVC material components

in extremely cold climates where the insulating layer or external protection severe very Brittle and easy exposure to cracks

2 - One of the fundamental flaws in the aluminum conductors is the layer of solid thin film of oxide on the surface of the connector , and despite the fact that this layer provide protection against erosion of Mosul, but they cause many problems , especially when welding operations and plug and install the ends of the cable , and it must follow the technical bulletins own installing cables aluminum with precision and can be obtained from these releases factories cables.

3 - The lack of sharp corners because it may cause damaging the cable during withdrawn within the Hungarian .

4 - Do not expose the cable to a strong strain of more than allowed during the process of withdrawing.

5 - tighten the ends of the cable lock to prevent the ingress of water or moisture to the inside , and access to the heart and increase the importance of this point if the cable placed in an environment exposed to water or moisture.

Tests performed on the low vpltage cables

Although most of the tests for the cables are in the factory , but it must make some tests upon receipt and after installation and the most important of these tests :

1 - Dimensions: Diameter is measured in conductor and the thickness of the insulation and the cover and the rest of the components of the cable carefully .When receiving and using the special micrometers. We must make sure that they conform to the specifications given by the factory should also be of interest, in particular, a thickness of the insulating and matching it with the standard specifications

2 - resistance and capacity of the separation : is measured resistance insulating capacity using the devices and methods of measuring normal and can perform this test to easily measure the resistance between each conductor and casing and between each conductor and the earth and all deliverers can make this measurement after installation and then after operating at periodic intervals.

3 - high voltage test : This is the test shed voltage on the cable and then raise the voltage up to four times the effort insulation rated for a period of 15 minutes , either at one stage or several stages and can perform this test using a constant voltage or voltage AC and preferred to use the effort hard , especially after the installation of the cable.

ConclusionThe electrical power is transmitted through ,underground cables or

overhead lines .Electricity transmission or electricity distribution network is intended

to process the transfer of electrical energy generated by the power plant to the direct beneficiaries, are electricity transmission through the network provided that they are feeding on each common unit, does not have any station between the beneficiary and the beneficiary last .

The cost of using cables is very high compared with the over head transmission lines,

But we can’t use the transmission lines within the cities to their large size and large space to be occupied.

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