![Electrical Thumb Rules You MUST Follow, part 7]( "Electrical Thumb Rules You MUST Follow, part 7")
Electrical Thumb Rules You MUST Follow, part 7 (photo by joy russell via Flickr)
Continued from: Electrical Thumb Rules You MUST Follow (Part 6)
8 electrical thumb rules to follow:
- Overhead conductor / cable size
- Transmission / distribution line (span, height of tower)
- Types of towers
- Tower swing angle clearance (metal part to live part)
- Cable coding, IS 1554 (A2XFY, FRLS, FRPVC, FRLA, PILC)
- Corona ring size
- Load as per Sq.Ft
- Size of ventilation shaft
1. Overhead conductor / cable size
| Voltage | Overhead Conductor | Cable Size |
| 33 KV | ACSR-Panther/Wolf/Dog , AAAC | 150,185,300,400,240 mm2 Cable |
| 11 KV | ACSR-Dog/Recon/Rabbit , AAAC | 120, 150,185,300 mm2 Cable |
| LT | ACSR-Dog/Recon/Rabbit , AAC, AAAC | 95,120, 150,185,300 mm2 Cable |
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2. Transmission / distribution line (span, tower height)
| Span | Height of Tower |
| 400KV = 400 Meter | 400KV=30Meter (Base 8.8 Meter) |
| 220KV = 350 Meter | 220KV=23Meter (Base 5.2 Meter) |
| 132KV = 335 Meter | 220KV Double Circuit=28 Meter |
| 66KV = 210 Meter | 66KV=13Meter |
| Conductor Ampere | Voltage wise Conductor |
| Dog = 300Amp | 400KV=Moose ACSR=500MVA Load |
| Panther = 514Amp | 220KV=Zebra ACSR=200MVA Load |
| Zebra = 720Amp | 132KV=Panther ACSR=75MVA Load |
| Rabbit = 208Amp | 66KV=Dog ACSR=50MVA Load |
| Moose = 218Amp | |
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3. Types of Towers
| Type | Used | Angle/Deviation |
| A | Suspension Tower | Up to 2° |
| B | Small Angle Tower | 2° to 15° |
| C | Medium Angle Tower | 15° to 30° |
| D | Large Angle / Dead End Tower | 30° to 60° & Dead End |
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4. Tower Swing Angle Clearance (Metal Part to Live Part)
| Swing Angle | Live Part to Metal Part Clearance (mm) |
| 66KV | 132KV | 220KV | 400KV |
| 0° | 915mm | 1530mm | 2130mm | 3050mm |
| 15° | 915mm | 1530mm | 2130mm | - |
| 22° | - | - | - | 3050mm |
| 30° | 760mm | 1370mm | 1830mm | - |
| 44° | - | - | - | 1860mm |
| 44° | 610mm | 1220mm | 1675mm | - |
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5. Cable Coding, IS 1554 (A2XFY/FRLS/FRPVC/FRLA/PILC)
| A | Aluminium |
| 2X | XLPE |
| F | Flat Armoured |
| W | Wire Armoured |
| Y | Outer PVC Insulation Sheath |
| W | Steel Round Wire |
| WW | Steel double round wire Armoured |
| YY | Steel double Strip Armoured |
| FR | Fire Retardation |
| LS | Low Smoke |
| LA | Low Acid Gas Emission |
| WA | Non Magnetic round wire Armoured |
| FA | Non Magnetic Flat wire Armoured |
| FF | Double Steel Round Wire Armoured |
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6. Corona Ring Size
| Voltage | Size |
| <170 KV | 160mm Ring put at HV end |
| >170 KV | 350mm Ring put at HV end |
| >275 KV | 450mm Ring put at HV end & 350 mm Ring put at Earth end |
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7. Load as per Sq.Ft
| Type of Load | Load/Sq.Ft | Diversity Factor |
| Industrial | 1000 Watt/Sq.Ft | 0.5 |
| Commercial | 30 Watt/Sq.Ft | 0.8 |
| Domestic | 15 Watt/Sq.Ft | 0.4 |
| Lighting | 15 Watt/Sq.Ft | 0.8 |
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8. Size of Ventilation Shaft
| Height of Building in meter | Size of ventilation shaft in sq meter | Minimum size of shaft in meter |
| 9.0 | 1.5 | 1.0 |
| 12.5 | 3.0 | 1.2 |
| 15 and above | 4.0 | 1.5 |
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