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CABLE AND LAYING

-B. PrasadChartered [email protected]

Cable cut view

TYPE OF CABLE BASED ON CONSTRUCTION

Coaxial cableMineral-insulated copper-clad cableTwinax cableFlexible cablesNon-metallic sheathed cable (or nonmetallic building wire, NM, NM-B)[1]Metallic sheathed cable (or armored cable, AC, or BX)[1]Multicore cable (consist of more than one wire and is covered by cable jacket)Shielded cableSingle cable (from time to time this name is used for wire)Twisted pairTwisting cable

Cable for electrical PVC cable upto 3.3KVXLPE cable upto 33KV LT and HT ABC cable Instrumentation cable Concentric core cable Flexible cable & wire FR/FRLS/LSOH cable Fire survival cable Under water cable

Elastomer Trailing cable Locomotive cables Ship wiring cable Wind mill cable/solar cable Welding cable Mining cable LFH cable and wire Fire survival cable EPR, Silicon, EVA cables

Telecom PIJF cable5-2400 pairIndoor telephone cable QUAD/PCM cable Optical fibre cable Armoured/duct/aerialTorpedo cable TOW cableComposite cable

Fiber-Optic CableAdvantages:It operate at high speedsIt has a large carrying capacityThe signals can be transmitted further without being strengthened.It is immune to interference caused by electromagnetic noise such as radios, motors, or other nearby cables.It is cheaper to maintain.You do not have to worry about grounding1 the cable.Disadvantages: The cable is more expensive than copper cables.It is difficult to install.

Construction of cable

Construction of XLPE

Construction of EHV XLPE single core

XLPE has replaced conventional cable

Insulating material PVC (Polyvinyl Chloride) PE (Polyethylene)XLPE (Cross-Linked Polyethylene)EPR (Ethylene Propylene Rubber) LSF (Low smoke and fume)Polytetrafluoroethylene (PTFE)

Thermoplastic Rubber (TPR)Neoprene (Polychloroprene)Styrene Butadiene Rubber (SBR) Silicone Rubber Chlorosulfonated Polyethylene (CSPE)

Junction bus Electrical Junction BoxesWiring Junction BoxesElectric Junction BoxesPlastic Junction BoxesCable Junction BoxesPlastic Electrical Junction BoxesWeather proof junction boxesFlameproof junction boxes

Cable lug Material: copper & aluminiumConductivity: Copper 99.7% iacs Aluminium 61.2% iacs (1050).

Cable lug ---contd

Cable manufacturers Name of manufacturer Brand N.C cable industries National Evershine Electric Works ECKOElectric Cable Industries ECI Paragon Cable Companyparagon Surya Power Limited ALCABNational insulated cable co. NICCOIndian cable company INCAB Aluminium industries limited ALIND R.K Electrical KALINGAPolycab Industries POLYCABPlaza Cable PLAZA Empire Cable Industries EMPIRE Hovels cable HAVELLCable corporation of India CCI Kei Industries LimitedKEI

Historical progress of cable technology

Historical voltage development in country

Indian and international standard

Reduction in insulation thickness

Metallic sheath

Lead sheath construction

Electrical Resistivity

Material Resistivity (-cm@20 deg.C)Copper 1.724Aluminium 2.826Steel 13.8Lead 21.4

Density of material

Importance of cable installation A poor installation creates unreliable serviceother agency my damage the cable.Telephone cable, communication cable, water line, gas pipe line may get affected

Location of cablingLaying direct in ground In pipes, Closed or Open ducts,

Cable trays and On surface of wall

Step of cable installation Route survey Permission Trial pits Pipe laying Material shifting, drum placement Trenching cable laying Bedding and tiling Backfilling Cable installation record tagging

Route survey Type of surface like footpath, PCC, RCC, soil typeHazardous like tree roots, pillars, sever line, drain, bus stop, water pipe, gas pipeCable root passing from private property Cable root away from parallel running gas, water pipe, communication cable etcRoad crossing, over bridge, drain crossing

Trial pit Along the proposed cable root.Trial pit at the interval of 15-20 meter

Permission Before starting the excavation permission to be taken Railways Traffic police and defence Forrest department Communication and gas authority Other service department if any

Digging To display Men at work Don't damage the other cableLeast use of pickaxe and chiselCorrect Depth depending upon voltage grade

Depth of cable LT cable (1.1KV) 0.75 m HT cable (11KV) 0.90 m HT cable (33KV) 1.20 m Sand - covered with 150 mmWidth of the trench - 350 mm minimumLoop approximate -3 meter each side

Minimum bending radius

Voltage rating PILC cable PVC & XLPE cable KVSingle core Multicore Single core Multicore Upto 1.120D15D15D12D1.1 to 11 20D15D15D15DAbove 1125D20D20D15D

Pipe laying if cable crossing the road, gate, railway track, water line Type of pipe: GI, cemented, HDPE pipeEnds to be sealed to avoid choking, clogging.Standard depth of pipe: 1m across the road, 1.8 m across railway track.Standard size of pipe: 1.5 times of cableSpare pipe: for future expansion , Ends to be sealed

Bedding Before and after cable laying and jointing work is over a bedding of sieved earth or river bed sand of 100 mm depth both below and above the cable.Keep distance between two cable in single trench.Avoid zig-zag

Cable under bed/on support

CABLE LAYING IN TRAY

Cable laying on rack

Tagging on cable

Use barricading tape

Cable handling

Cable handling tools Jack Roller Drum trailer Crimping tool

Cable installation record Type of cable and its sizeVoltage levelCable no, drum no.Date Rout map, location of cable joint Installation test record like IR value, HV test if any

Testing of cable installation Insulation resistance test High voltage test Continuity testValue IR value : minimum 1M-ohm/KVHV test value : minimum 1KV/KV +1 for 5 minutes

Cable testing Type test Routine test Pre-commissioning test A) for new cable after installation B) After repairing the breakdown

Insulation resistance test Before jointing and after jointing

S no. Voltage Test voltage New installation Old installation Recorded IR value 1upto1.1KV 500 V dc for 1 min.1.0KV dc for 1 min.50M211KV 1.0KV dc for 1 min.2.5KV dc for 1 min200M333KV2.5KV dc for 1 min.5.0 KV dc for 1 min.500M

466KV5.0 KV dc for 1 min.5.0 KV dc for 1 min.500M

High voltage test value

Sr.Voltage level of the cable under testTest voltage Observed leakage current (maximum)New installation Old installation New installation Old installation 1upto1.1KV 3KV 660V0.5mA2mA

211KV 18KV 6.5KV 0.5mA2mA333KV60KV 19.5KV 0.5mA2mA466KV115KV 38KV0.5mA2mA

Cable testing at manufacturers works a) Tensile Test (For Aluminium Conductor)b) Wrapping Test (For Aluminium Conductor)c) Annealing Test (For Copper Conductor)d) Conductor Resistance Teste) Test for thickness of Insulation & Sheathf) High Voltage Testg) Insulation Resistance Testh) Tensile Strength & Elongation at break test forInsulation and SheathI) Hot Set Test - (for XLPE Insulation only)j) Partial Discharge test (for H.T. Screened cable)

Cable short circuit ISC = kA / tK= ConstantAl -- 0.094 (XLPE)Cu -- 0.14382 (XLPE)A - Cross Section Area (mm 2)T- Time in seconds

Earthing Metal screen (if any) and armour of cable to be earthed.All metal pipes in which cables have been installed need to be earthed.

Corrosion Types Encountered With Power CablesAnodic Corrosion (Stray DC Currents)Cathodic CorrosionGalvanic CorrosionChemical CorrosionAC CorrosionLocal Cell CorrosionOther Forms of Corrosion

Voltage drop calculation

For DC and single phase AC two wire systemsVoltage drop = (2xIxLxRxt)/1000Where I = current in ampere L = length of cable in meter (one conductor only)R = resistance of one conductor from table t = temperature correction factor

Voltage drop ----contd For three phase AC systemsVoltage drop = (1.732xIxLxRxt)/1000Note: formula is applied when power factor is unity. Power factor to be considered in load and reactance to be considered.Note:formula is applied when power factor is unity. Power factor to be considered in load and reactance to be considered.

Resistance

Voltage drop value in%

Failure in cable Internal and surface discharge may result failure of the insulation.Proper drying, due to low /bad quality of fluid. Ingress of moisture and degradation of insulation.Crack in the sheath, due to abnormal temperature, electrical stress, mechanical tension. Voids due to partial discharge.Overheating, deformation, ionization etc. NB: permitted size of voids in cable to be 22-25 micron.

Root marker Aluminium Cast Iron Material with Standard or Custom designFibreglass Reinforced Plastic [FRP]

Cable tape Size: Length: 5Y, 5m, 10Y, 10m, 20Y, 20m. Width: 12mm, 15mm. 17mm, 18mm, 19mm, 25mm, 48mm, 50mm.

Cable gland Type of CableGland SizeEntry Type/Thread Specification of applicationIngress Protection required.Material

Parts of gland

Type of Gland A1 and A2 Type Cable GlandBW Type Cable GlandCW Type Cable GlandSingle Compression Cable GlandDouble Compression Cable GlandFlameproof Cable Glands

E1W Type Cable GlandFlange Type Cable GlandPG Type Cable GlandMarine Type Cable GlandMetric Threaded Cable GlandWeather Proof Cable Glands

Cable ties materialNylon 66 Nylon 66 UV Stabilized Nylon 66 Heat Stabilized Polypropylene Tefzel

DIN rail and terminal block

De-rating factor Thermal insulation factorsAmbient temperature Group factor

Depth of laying Thermal resistivity

Depth of laying (cm)7590105120150180Cable size < 25 sqmm10.990.980.970.960.95Cable size < 300 sqmm10.980.970.960.940.93Cable size 300 sqmm10.970.960.950.920.91

Busbar Material : Aluminium Copper Technical specificationRating Current:3200Amp.System:415Vac, TPN, 50Hz.Fault Level:50KA. For 1 Sec.Operation Temp:40 C rise over 45 C ambient

Cable entry Indoor application:Top and bottom both Outdoor application: Only bottom

Conduit Fittings & Accessories

Construction: Galvanized steel, helically wound, Flexible Conduit System.Temp: -50 C to +200 CFeatures: Highly Flexible and mechanical strengthIP: IP4

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