Steel Tower
The lattice steel structure carrying the mechanical loads from conductors, insulators and wind: legs, main body, diagonal members, tower peak and base plates.
Overhead Transmission Line Systems
A technical overview of the overhead transmission line system: towers, cross-arms, conductors, insulators, shield wires, hardware, foundations and earthing — with standard configurations by voltage.
Classification
Tower Types by Voltage
From 400 & 132 kV high-voltage transmission down to 33 kV sub-transmission and 11 kV distribution on the Iraqi national grid.
400 kVTransmissionIraqi MoE 400 kV specification · IEC
XATangent / SuspensionStraight line · 0°
XBLong Span / Small AngleDeviation 0°–10°
XCAngleDeviation 0°–45°
XDTerminal / Dead-EndDeviation 0°–90°
XETranspositionPhase transposition along the line
132 kVTransmissionIraqi MoE specification · IEC
2S2Tangent / SuspensionStraight line
2T2AngleAngle change (medium angle)
2E2Angle / SectionAngle or line section
2R2CrossingCrossing — line passes over
2K2Under-CrossingUnder-crossing — line passes under
33 kVSub-transmissionIraqi MoE specification · IEC
33SSuspensionStraight line
33AAngleAngle change
33TTerminal / Dead-EndLine termination / dead-end
11 kVDistributionDistribution poles · Iraqi MoE specification
11SSuspension PoleStraight line
11AAngle PoleAngle change
11TTerminal / Dead-End PoleLine termination / dead-end
Reference Chart
Transmission Tower Types in Iraq
A complete chart of every voltage level with codes, dimensions and specifications.
Technical Data
Typical Technical Data
Indicative values, finalized per project design, loads and terrain.
| Voltage (kV) | Circuits | Tower height approx. (m) | Normal span (m) | Max span (m) |
|---|---|---|---|---|
| 400 | Single | 30–55 | 350–450 | 600–700 |
| 400 | Double | 40–65 | 400–550 | 700–900 |
| 132 | Single | 18–30 | 200–300 | 350–450 |
| 132 | Double | 22–35 | 250–350 | 450–550 |
| 33 | Single | 12–18 | 100–150 | 150–250 |
| 33 | Double | 14–22 | 120–180 | 180–280 |
| 11 | Single | 8–12 | 50–80 | 80–120 |
| 11 | Double | 9–14 | 60–100 | 100–150 |
Components
Main System Components
Cross-Arms
Horizontal arms holding the insulator assemblies and conductors, maintaining electrical clearance between phases and the tower.
Phase Conductors
The power-carrying wires. Most common is ACSR (aluminium with steel core); each phase may use several bundled subconductors at higher voltages.
Insulators
Separate the energised conductor from the grounded tower: suspension strings, tension strings, composite (polymer) and porcelain/glass disc insulators.
Shield / Earth Wire (OPGW)
Sits above the conductors to intercept lightning and route it to ground. Modern systems use OPGW combining shielding with optical-fibre communication.
Hardware & Fittings
Suspension and tension clamps, compression fittings, connectors, shackles, links, corona rings and bundle spacers.
Vibration Dampers
Attached to conductors to reduce wind-induced vibration (e.g. Stockbridge dampers); important on long spans to prevent fatigue.
Foundation & Earthing
Reinforced-concrete foundations anchoring the tower legs, with an earthing system (rods and ground paths) to dissipate lightning and fault currents.
Common Conductor Types
ACSR AAC AAAC ACAR HTLS
Conductor choice depends on voltage, span length, terrain and load requirements.
Key Functions
- Transmit electrical power safely and reliably
- Withstand mechanical loads (wind, ice, tension)
- Maintain electrical clearances and insulation
- Protect against lightning and faults
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