Abstract of CPWD Internal Electrification Part-1
- Per Circuit Not more than 10 Points of Lighting or Total 800Watt which is less
- For Residential Per Circuit Less than 2 No of 5A/15A Plug Socket
- For Non Residential Per Circuit Less than 1 No of 5A/15A Plug Socket
- In Residential wiring ,wiring of Socket outlet shall be done by copper Cable only
Min Size of Wire
- For Lighting Circuit Smallest size of conductor shall be 1.5 Sq.mm
- For Power Circuit Smallest size of conductor shall be 4 Sq.mm
- 5A/6A or 15A/16A Socket shall be installed at following heights:
- For Non Residential building 23cm above Floor,
- For Kitchen 23cm above Platform,
- For Bathroom not Socket is provided in bathroom MCB/IC will be 2.1 meter from fixed appliance and at least 1 meter away from Shower.
- Operating Rod/Handle of Distribution Board at the height of min 2meter
- Clear Distance in front of Switch Board/D.B shall be min 1 meter.
- If there may be bare connection at back of Switch Board than space behind S/W shall be either less than 20cm or more than 75cm.
- No fuse Body shall be mounted within 2.5 com edge of D.B or Panel
- Clearance between 2.5 cm is maintained between opposite polarity.
- Switch Box or Regular Box shall be mounted normally 1.25 meter from floor level.
- For Fan Hook in concrete roof 12mm diameter MS Rod in ‘U’ Shape, horizontally Leg at Top at least 19 cm on either side.
- Connection between adjustment Building (Out House, Garages) (Safety Clearance)
- If the distance with adjustment building is less than 3 meter and there is no any Road interval than GI pipe of suitable size shall be installed. This pipe shall be exposed on wall at height of not less than 2.5 meter.
- If the distance with adjustment building is more than 3 meter and there is any Road interval than GI pipe of suitable size shall be installed. This pipe shall be exposed on wall at height of not less than 4 meter.
- Shall be used for Industrial wiring, Heavy mechanical Stress, shall be ISI marked, The Thickness shall not be less than 1.6mm(16SWG) for conduits up to 32mm Diameter and not less than 2mm (14SWG) for conduit above 32mm Dia.
- No steel conduit less than 20 mm Diameter shall be used.
- For rigid Conduit IS:2509 /IS:3419 and For Flexible Conduit IS:6946.
- All Metallic conduit accessories shall be threaded type (Not pin grip, clamp grip)
- Saddle for surface conduit work on wall shall not less than 0.55mm(24 gauge) for conduit up to 25mm Diameter not less than 0.9mm (20 gauge) for larger Diameter
- Fore Cast Boxes: Wall thickness shall be at least 3mm.
- For Welded mild Steel Box: Wall thickness shall not be less than 1.2mm (18 gauge) for Boxes up to size 20cmX30cm. Above This size 1.6mm (16guage)thick MS Boxes shall be used.
- Clear depth of Out less Box shall not be less than 60mm.This will be increased as per mounting of Fan regulator
Bends in Conduits
- Bending radius not less than 7.5 cm
Fixating Conduits on Surface
- Conduits shall be fixed by saddles not less than 1meter interval but in case of coupler/Bends in either side of saddles, The saddle shall be fitted 30 cm from fitting.
- Depth of Junction Box shall be min 65mm as per IS: 2667.
- GI fish wire of 1.6mm/1.2mm(16SWG) shall be used
Non Metallic Conduit Accessories
- Normally grip Type.
- PVC Box IS:5133 (PartII) thickness not less than 2mm,Clear depth of PVC Boxes not less than 60mm.
Non Metallic Surface Conduit
- Conduits shall be fixed by saddles not less than 60cm interval but in case of coupler/Bends in either side of saddles, The saddle shall be fitted 15 cm from fitting.
- Bulbar shall be 100A,200A,300A,400A,500A,600A,800A
- The Cross-section area of Bus bar shall be same as Phase Bus bar (Up to 200A) for higher Capacity Neutral Bus bar must be not less than half cross section areas of Phase Bus bar.
- Bus bar shall be suitably installed with PVC sleeve/Tap.
- Bus bar Chamber shall be fabricated with MS angle for Frame work and sheet steel of thickness not less than 1.5mm.
- Minimum clearance between phases to earth shall be 26mm and phase to phase shall be 32mm.
Bus bar Trucking
- Bus bar Trucking are generally used for interconnection between T/C over 500KVA/D.G set over 500KVA and their switch Board Panel.
- Bus bar Trucking enclosure sheet steel of min 2mm thickness
- Type of earthling are Pipe earthling/Plate earthling/Strip earthling
- Length of Buried strip shall not be less than 15meter.
- Two copper strip, each size 50mmX5mm shall be provided as each bus bar in 11KV S/S or D.G generally.
- Each strip should be connected separately to earth.
- Two no of Body earthling of T/C, Panel, D.G are connected to earth Bus.
- Neutral Leads of T/C, D.G shall not be connected to earth Bus.
- The minimum Cross-section are of protective conductor(Not contained within cable or wire) 2mm Dia(14SWG) for Copper, 2.5mm Dia (12SWG) for G.I, 2.24mm Dia (13SWG).
Earthing Pit shall not be closer than 1.5meter from Building.
- Top of Pipe earthling electrode shall not be less than 20cm below the ground level.
- Plate electrode shall be buried in ground with face vertical and it’s Top not less than 3meter below ground level.
- The strip of earthling electrode shall be buried in trench not less than 0.5m deep.
- If strip electrode cannot be laid in straight length. It may be Zigzag with deviation up to 45 Degree from axis of strip.
- In Plate Earthing Diagram of water pipe shall not be less than 20mm and in Pipe earthling reducer of 40mmX20mm shall be used.
- Earthing Pit Size shall be not less than 30cmX30cmX30cm.
- Thickness of MS cover of earthling pit shall be not less than 6mm and having locking arrangements.
- Earthing resistance of each electrode shall be less than 5Ω and for Rocky Soil not less than 8Ω
- Earthing conduit for earthling wire shall be Medium class 15mm Diagram GI pipe and for Earthing Strip shall be medium class 40mm Diagram GI Pipe.
Conductor Clearance (min) (Different Voltage)
- When two conductor of different Voltage are erected on same support min clearance between LV/MV and 11KV shall be min 1meter.
Conductor Clearance (min) (Different Support)
- A Clearance not less than height of tallest support may be maintained between parallel overhead line on Different support.
- When two overhead line cross each other vertical clearance between LV/MV and 11KV shall not be less than 1.25meter and for LV/MV and 33KV line shall be not less than 2meter.
Conductor Clearance (min) (Across Road)
- Min Conductor Clearance across Road: For LV/MV Line is 5.8 meter and for HV Line 6.1meter
Conductor Clearance (min) ( Along Road)
- Min Conductor Clearance along Road: For LV/MV Line is 5.5meter and for HV Line 5.8meter
Conductor Clearance (min) (Along/Across)
- Min Conductor Clearance along/across Road: For LV/MV/HV up to 11Kv (Bare Conductor) Line is 4.6meter.
- Min Conductor Clearance along/across Road: For LV/MV/HV up to 11Kv (Insulated Conductor) Line is 4.0meter.
- Min Conductor Clearance along/across Road: For HV (11Kv to 33Kv) Line is 5.2meter.
- Min Conductor Clearance along/across Road: For EHV (above 33Kv) is 5.2meter + 0.3 meter for every 33KV (Not less than 6.1).
Conductor Clearance (min) (From Building)
- Min Conductor Vertical Clearance above Building: For LV/MV Line is 2.5meter from highest Point.
- Min Conductor Horizontal Clearance near Building: For LV/MV Line is 1.5meter from nearest Point.
- Min Conductor Vertical Clearance above Building: For MV/EHV (up to 33KV) Line is 3.7meter from highest Point.
- Min Conductor Vertical Clearance above Building: For MV/EHV (above 33KV) Line is 3.7meter + 0.3meter for every 33KV
- Min Conductor Horizontal Clearance above Building: For MV/EHV (Up to 11KV) Line is 1.2meter.
- Min Conductor Horizontal Clearance above Building: For EHV (Up to 33KV) Line is 02meter.
- Min Conductor Horizontal Clearance above Building: For EHV(above 33KV) Line is 2meter + 0.3meter for every 33KV
Conductor Clearance (min) (Cable crossing):
- The horizontal and vertical distance between Power and Communication cable shall not be less than 60cm.
Conductor Clearance (min) (Railway crossing):
- After taking approval of railway authority, Cable under railway track shall be min 1meter from bottom of sleeper under RCC or cast Iron Pipe.
- Cable in parallel to Railway track shall be min 3meter far away from center of nearest Track.
- For single cable: For below 11Kv.Min length of Trench shall be 35cm and depth shall be min 75cm ( with sand cushioning of 8cm at bottom +Cable+ protective covering/Sand cushioning of 17cm above Cable) and without Cushioning Depth shall be 75cm+25cm.
- For single cable: For above 11Kv.Min length of Trench shall be 35cm and depth shall be min 1.2meter ( with sand cushioning and protective covering).
- For multi cable in horizontal level: Min distance between two cable shall be 20cm and min distance between cable and edge of trench on both side shall be 15cm
- For multi cable in Vertical level: Min distance between two cable shall be 30cm.(min Sand cushioning at bottom of trench shall be 8cm +Cable+ min Sand cushioning of 30cm+Cable+protective covering/Sand cushioning of 17cm above Cable)
- For LV/MV cable cushioning is not required where there is no possibility of mechanical damages.
- Extra loop of cable at end shall be 3meter for cable termination/Joints.
Cable Route Marker
- Cable Route Marker shall be min 0.5meter away from cable trench at the interval not exceeding 100meter parallel.
- Plate Type Cable Route Marker shall be made of 100mmX5mm GI/Aluminum Plate welded/Bolted on 35mmX35mmX6mm Iron angle of 60cm Long.
- Cement Concrete (C.C) type marker shall be made in formation of 1:2:4.
Cable Bending Radius
Cable Lying in Pipe
- For Single Conductor Shall be min 10cm Diameter and more than Two Cable shall be min 15cm Dia.
Cable in Road Crossing
- In Road Crossing Cable shall be laid min 1 meter below Road in Pipe.
Cable Tray (Perforated)
- Cable Tray may be fabricated by two angle irons of 50mmX50mmX6mm as two longitudinal members with cross bracing between them 50mmX5mm welded/Bolted at angle and 1 meter spacing of 2mm thick MS sheet.
Steel Tubular Pole
- 1/6 length of Steel Tubular Pole + 30 cm from base shall be coated with Black Bituminous paint on both internally and externally. The remaining portion of the pole shall be painted with Red oxide.
- LV/MV Line: MS angle iron of size not less than 50mmX50mmX6mm (4.5kg/meter)
- 11KV Line: MS angle iron of size not less than 65mmX65mmX6mm (5kg/meter)
- LV/MV Line: MS Chanel iron of size not less than 75mmX40mmX4.8mm(7.14kg/meter)
- 11KV Line: MS Chanel iron of size not less than 75mmX40mmX4.8mm(7.14kg/meter)
- For LV/MV Line: Min distance shall be 5cm between center of insulation pin and end of cross arm.
- For 11KV Line: Min distance shall be 10cm between center of insulation pin and end of cross arm.
Cross arm Length
Nom of Horizontal Con
Length of Cross Arm
- For LV/MV Overhead Line: Pin/Shackle Insulator and For 11KV Line Pin/Disc Insulator
- For Pin Insulator for LV/MV line: Stalk Length 135mm Shank Length 125 mm, min Load 2KN.
- For Pin Insulator for 11KV line: Stalk Length 165mm Shank Length 150 mm, min Load 2KN.
- D clamp shall be made of MS Flat size of 50mmX6mm,height of 75mm Galvanized and only used for vertical configuration for LV/MV Line only.
Pole Top Clamp
- Pole Top clamp made from Flat iron 50mmX8mm.
Stay wire Rod
- Stay wire Rod shall not be less than 1.8 m Long and 19mm Dia. Anchor Plate shall not be less than 45mmX45mmX7.5mm.
Overhead Conductor (min)
- For LV/MV Line: AAC(All Alu. Conductor) 7/1/2.21mm, ACSR 6/1/1/2.11mm, AAAC (All Alu. Alloy Conductor) 7/2.09mm(20Sqmm)
- For 11KV/33KV Line : AAC(All Alu. Conductor) N/A, ACSR 6/1/1/2.11mm, AAAC (All Alu. Alloy Conductor) 7/2.56mm(30Sqmm)
- Binding Wire with insulator shall be done with 2.6mm(12SWG) soft aluminum wire.
Earthing in Overhead Line
- Earthing wire shall not be less than 4mm(8SWG) and min 3 earthling Pit per KM shall be required.
- If there is no Continuous wire for earthling in overhead line than each pole should be earthed.
- For LV/MV Line on Same Support Vertical distance: Between Phase to Earth shall be min 30cm and Between Phase to Phase min 20cm
- For LV/MV Line on Same Support Horizontal distance: Between Live wire on either side of support shall be 45cm.
- For LV/MV Line on Same Support Horizontal distance: Between Live wire on same side of support shall be 30cm.
- For LV/MV Line on Same Support Horizontal distance: Between central of pin insulator to end of cross Arm shall be 05cm.
- For HV Line in Triangular Configuration for 11KV/33KV Line shall be min 1.5meter.
Overhead Line Struts
- The Pit for Struts shall be located not less than 1.8meter from pole side. The depth of Pit shall be at least 1.2meter
- All Support carrying HV Line shall be fitted with Danger Board( IS:2551-1982) at height of 3meter.
Anti Climbing Device
- For HV Line (IS:278-1978) having 4Point Barbs 75mm+12mm apart weight 128/125 gm/meter shall be wrapped helically with pitch of 75mm around Limb of Pole height of 3.5meter to 5 to 6 meter.
- Looping Bus shall be fabricated from MS Sheet of 1.6mm(16SWG) thickness, Min Size 250mmX200mmX100mm for single cable entry and for 250mmX300mmX100mm for more than two cable entry
- Feeder Pillar shall be fabricated min 2mm thick MS sheet and hinged type double door at front side. If width of Pillar shall be less than 60cm than single hinged type door shall be permitted.
- Min height of Pedestal of Feeder Pillar shall be not less than 45cm and 1 to 2 meter height from Road Level.
- Each Feeder Pillar shall be earthed with 2 no of Earthing electrode
- Clear Height of S/S Building shall be min 3.6meter.
Area of Sub station
Total Transformer Room Area
Total S/S Area (Transformer, HT/LT Panel without D.G)
36 Sq meter
130 Sq meter
54 Sq meter
172 Sq meter
39 Sq meter
135 Sq meter
58 Sq meter
181 Sq meter
39 Sq meter
149 Sq meter
58 Sq meter
197 Sq meter