Training Introduction

Training IntroductionElsewedy Cables Ethiopia PLC11- Voltage :-Any electric equipment is denoted by its operating voltage , cables are denoted as U0/U( U max) KV where :_Uo :- is the rated power frequency voltage between conductor and earth or metallic screen for which cable is designed.U : is the rated power frequency voltage between conductors for which the cable is designedUmax : is the max value of the highest system voltage for which the equipment is designed

For example : Saying 0.6/1 (1.2) Kv cable means that Uo (Phase voltage) = 0.6 KvU ( Line voltage) = 1 KvU max ( max Voltage ) =1.2 kv

Cable is defined by its line voltage as when saying 15 kv cables we mean 8.7/15 ( 17.5 ) KvPower cables1- Overhead transmission lines O.H.T.L

Low voltage 2- Under ground power cables

1) Voltage Grades of L.V. Cables:300/500 V [Both sheath & non-sheath cable (insulated wires)]

450/750 V [non-sheathed cables (insulated wires)]

600/1000 V or 0.6/1 kV (Sheathed cables)Types of overhead conductorsACC( ALL CU. CONDUCTOR)

2- AAC(ALL AL. CONDUTOR)

3 AAAC (ALL AL. ALLOY COND.)

4 ASCR (ALL ALLOY STEEL RIENFORCED)

2) Comparison between O.H. conductors &U.G. cables:O.H. CONDUCTORU.G. CABLES- Widely in transmission Network & distribution net work in urban areas- Widely used in side towns where safety is requires- Out door application- Both outdoor & Indoor (inside industrially residential & Building, wiring & lighting application)- Considered of less cost compared with underground cables-Considered of higher cost compared with O.H conductors- Include processes of1) Drawing section2) Stranding section - Includes processes of1) Drawing section 6) Armoring section 2) Stranding section 7) Separation section 3) Insulation section 8) Lead section 4) Assembly section 9) Sheathing section 5) Bedding section Cable Construction1) Conductor :- is the element responsible to deliver the power or signals from one point to another with minimum losses during transportation.

Types of conductors According to materials : 1) Copper :- Has excellent electrical and mechanical prosperities compared with AL Conductivity 100 %Resistivity 17.241 ohm.mm2/kmDensity is 8.89 g/cm3, so copper weight is more than AlCopper is more expensive than AL 2) Aluminum :-Has less mechanical and electrical properties than CopperConductivity 61%Resistivity 28.264 ohm.mm2/kmDensity 2.703 g/cm3Aluminum is cheaper than Copper Types of conductors according to construction1) Solid round conductors

2) Flexible conductor

3) Stranded round conductor

Types of conductors according to shape1) Round conductors

2) Round Compact conductor

3) Sector conductor

Isolates the conductors from each othe and from surroundingsInsulationTypes of insulationPoly VinPlastic yl chloride ( PVC ) :Thermo material Maximum operating temp. is 70 C Maximum S.C. temp. 160 C for C.S.A. 300mm2 Maximum S.C. temp. 140 C for C.S.A. >300mm2

Cross linked polyethylene ( XLPE ):Thermosetting material Maximum operating temp. is 90 C Maximum S.C. temp. 250 C

Ethylene propylene Rubber ( EPR ) :Thermosetting material Maximum operating temp. is 90 C Maximum S.C. temp. 250 C

Cores IdentificationColors of cores are usually as following:Single core : Natural, Red, etc2 cores: Red & Black3 cores: Red, Yellow & Blue4 cores: Red, Yellow, Blue & Black5 cores: Red, Yellow, Blue, Black & GreenGrounding wire: Green & Green/YellowMore than 5 : (Black + No. or White + No. ,etc)

Cores identification can be as per customerAssembly ProcessIt is the process to assemble the insulated cores together with suitable lay length and direction to form a round assembled cores, if needed, we apply polypropylene fillers to fill the space between cores, so it will make the assembled surface round and then wrapped with polypropylene tape or any suitable tape to form a compact round cable.Bedding ProcessThe main function of the Bedding is to give mechanical protection for insulation in case of armored cables only.

Material : Extruded poly vinyl chloride ( PVC ) when there is higher mechanical hazard we use polyethylene ( PE )Armouring ProcessThe Armouring is used as mechanical protection for direct burial cables.

It is used as an earthing conductor in some Networks .

Armouring ProcessMaterial :

The steel is the suitable material for multi-core cables

Steel is applied in one of the following forms : a) Tapes : Double tapes are applied helically around the bedding of cables with 50 % gap.

b) Wires : Number of wires with the specified diameter is to cover the bedding surface helically .

In case of single core cables steel is replaced with non magnetic material like Aluminum to reduce the magnetic losses (eddy current) .

Sheath ProcessIt is outer jacket of the cable , its main function is mechanical protection.

Material : Poly Vinyl Chloride (PVC) , When there is higher mechanical hazard we can use Polyethylene (PE)colour: Black or as per customer requirements Special characteristics may be included such as:Anti-Termite resistantOil resistantChemical resistantAcids & Alkaline resistant etc.In case of mechanical hazard we can use polyethylene materials such asHigh Density Polyethylene [HDPE]

Medium Density Polyethylene [MDPE]

Linear Low Density Polyethylene [LLDPE]Recommendations for storage and transportation Basic RequirementsTerms2X cable diameter but at least 5 cm Distance between the outer cable layer and the head of the flangeThe cable ends have to be sealed during transport storage and laying to prevent ingress of waterCable sealing endThe cable ends should be tightened properlyTransportOnly suitable carriers shall be usedCarriersCable drums with flange diameters exceeding 1 m have to be transported with horizontal drum axisDrum axis positionOnly suitable carriers shall be usedLoading and unloading 25Basic requirementsTermsFilled-up cable drums shall be rolled on short distances over plain solid ground in the direction indicatedRolling the cable drumsShort cable lengths may be coiled to rings and transported and stored horizontally taking into consideration the the min bending radiusCable ringsRecommendations for storage and transportation Recommendations for cable LayingBasic requirmentsTermsThe cable route, the laying method and the operating conditions shall be taken into accountSelection of cablesCables shall be laid and operated in such a way that their prosperities are not endangered.Operating conditionsConcentration of cablesInfluence of external heatSpecific earth resistanceProtection against radiation of sunlightb) Leakage of stray currents and corrosionc) Movements of soil, vibrations and shakesd) The method of laying and the bedding material have to be selected in respect of the outer cable sheathe) Protection against outer influences e.g. chemical solvents.

Laying and operatingBasic requirementsTermsCables shall be protected against mechanical damages occurring after installation.Cables laid in ground are sufficiently protected against mechanical damages.A laying depth of at least 0.6 m respectively 0.8 m below road-surface is recommended. In case of lower laying depths the cables shall be protected by other means.

Protection of cablesInner diameter of ducts and pipes 1.5 times cable diameterIn case of several cables within one pipe the diameter of the pipe has to be so width that the cables do not block themselves.When steel pipes are used single-core cables belonging to a three-phase system have to pass through the same steel pipe.It is recommended to protect the pipe against the ingress of sand.Dimensions of ductsRecommendations for cable LayingBasic requirementsItemThe lowest allowed temperature of the cables during installation and mounting of accessories is -5 OCThis temperature is valid for the cable itself and not for the surroundings. In case the cables have a lower temperature than permitted they must be warmed up. Care has to be taken that the temperature remains above the permitted temperature during laying.Lower temperatures for cable laying Pulling forcea) Pulling headRecommendations for cable Laying

Basic requirementsItemsIt is assumed that the cable route is well designed for the laying procedure with well-established curves and a sufficient number of cable rollers. Special attention shall be paid to the requirement bending radiusThe pulling force shall be permanently supervised the pull-in procedure.Preparation of cable routeDuring installationSingle-core cables : 15 times the cable diameter- multi-core cables: 12 times the cable diameterBending radiusRecommendations for cable LayingStorage

Transport

De-reeling

Rewinding

Thanks Eng/ Ashraf Abd El-Raouf

Elsewedy Cables Ethiopia PLC