SOLAR TODO delivered a utility-ready Power Transmission Tower solution for a high-demand corridor in Colombo, Sri Lanka (6.93, 79.85)—a 10kV double-circuit overhead line requiring compact right-of-way, reliable wind performance, and durable corrosion resistance in a coastal environment.
Answer Capsule: SOLAR TODO installed 261 units of 25m tapered steel tubular poles for a ~16km 10kV double-circuit line in Colombo, engineered to IEC 60826 / GB 50545 wind loads and corrosion-ready hot-dip galvanizing.
Project Overview (Colombo, Sri Lanka)
Colombo’s dense urban fabric and coastal conditions create a demanding backdrop for overhead electrification: limited space for construction staging, frequent planning coordination, and long-term exposure to saline air and high wind events. For this corridor, the utility needed a transmission structure that could:
- maintain mechanical integrity under wind class 4 (40 m/s),
- support conductor and insulator geometry for a 10kV double-circuit arrangement,
- deliver corrosion protection suitable for coastal operation,
- simplify installation through standardized pole sections and bolted connections.
SOLAR TODO’s scope centered on supplying and engineering steel tubular transmission poles (NOT lattice, NOT FRP) designed as tapered monopoles with robust hardware interfaces for insulator strings and ACSR conductors. The final line length was ~16km across 60m span sections, using 261 poles of 25m height to achieve the required electrical clearances and mechanical performance.
Why a Steel Tubular Transmission Pole (NOT lattice) for Colombo?
In coastal cities like Colombo, transmission structures must be both structurally efficient and highly durable. SOLAR TODO selected a tapered round/dodecagonal steel tubular monopole approach (rather than lattice towers) because tubular poles reduce complexity in detailing, improve uniformity of galvanization coverage, and provide a clean load path for wind and conductor forces.
Key design intent for this project was to ensure that the pole system remains stable for the full service life while meeting international design criteria—specifically IEC 60826 for overhead line wind loading and GB 50545 for relevant structural requirements.
Deployment Design: 10kV Double-Circuit Line Configuration
This Colombo project used 261 × 25m tapered steel tubular poles configured for a 10kV double-circuit overhead line.
Electrical / Mechanical Geometry
- Phase spacing: 0.8m
- Ground clearance: 5m
- Span length: 60m
- Total line length: ~16km
- Insulator length: 0.5m
- Conductor type: ACSR 120
- ACSR 120 parameters: 470kg/km, max tension 38kN
The pole design included cross-arm brackets for insulator strings + ACSR conductors, enabling consistent conductor routing and maintaining the phase spacing required for safe operation. The structure’s accessories were selected to address field realities—climbing safety, grounding continuity, bird protection, and vibration control.
Wind Performance (IEC 60826)
Colombo’s coastal exposure makes wind loading a primary design driver. SOLAR TODO engineered the pole system for:
- Wind class 4: 40 m/s
- Compliance aligned to IEC 60826 (wind actions on overhead lines)
This ensured that conductor galloping/vibration risk and lateral load effects were addressed through the combination of structural stiffness and mechanical accessories.
Technical Specifications
- Quantity: 261 units
- Pole type: Steel tubular transmission pole (NOT lattice, NOT FRP)
- Height: 25m tapered steel tubular monopole
- Cross-section: tapered round or dodecagonal steel (tubular)
- Material grade: Q345 steel
- Corrosion protection: hot-dip galvanized
- Weight: ~25t/pole (1000kg/m)
- Conductor: ACSR 120 (470kg/km, max tension 38kN)
- Phase spacing: 0.8m
- Ground clearance: 5m
- Insulator length: 0.5m
- Span: 60m
- Total line: ~16km
- Accessories: climbing steps, cross arm, grounding, bird guard, vibration damper
- Foundation type: spread_footing
- Standards compliance: IEC 60826 / GB 50545
- Foundation concept (pole interface): concrete foundation with anchor cage and flanged bolt sections
Engineering & Fabrication Approach
1) Hot-dip galvanization for coastal durability
For Colombo, corrosion resistance is essential due to saline air and humid coastal conditions. The poles were manufactured from Q345 steel and finished with hot-dip galvanization to create a protective coating system that supports long-term asset performance.
2) Tapered tubular geometry for efficient load transfer
The 25m tapered monopole geometry is designed to handle lateral loads from wind while supporting the conductor arrangement for a 10kV double-circuit line. The tapered form improves structural efficiency and helps ensure consistent behavior across the full height.
3) Flanged bolt sections for controlled installation
To support field execution, the poles used flanged bolt sections. This approach improves erection quality by enabling accurate alignment and secure bolted connections during installation.
4) Foundation compatibility: spread_footing + anchor cage
The project specified a spread_footing foundation system with a concrete foundation and anchor cage, aligning structural loads with the ground conditions typical for urban corridors. This foundation strategy also helps manage settlement sensitivity and supports stable long-term operation.
Field Installation Notes in Colombo
Colombo’s infrastructure environment typically requires careful coordination for equipment access, work windows, and traffic management. SOLAR TODO’s pole system was designed to be practical for site execution:
- Standardized 25m pole units (261 total) reduce variability across the route.
- Bolted flanged sections support repeatable assembly procedures.
- Climbing steps and grounding hardware reduce safety and commissioning effort.
- Bird guards help mitigate avian-related risks that can lead to flashover events.
- Vibration dampers support mechanical stability under wind-driven conductor motion.
Results and Impact
The delivered configuration—261 × 25m steel tubular poles for a ~16km 10kV double-circuit line with 60m spans—was engineered to meet IEC 60826 / GB 50545 requirements for wind class 4 (40 m/s) and to maintain required clearances (0.8m phase spacing and 5m ground clearance).
Key outcomes from SOLAR TODO’s deployment approach include:
- System consistency across the corridor: 261 standardized pole units with uniform conductor/insulator interfaces.
- Mechanical robustness for coastal wind conditions: design alignment to IEC overhead-line wind action principles.
- Durability for long service life: hot-dip galvanized Q345 steel to resist corrosion in Colombo’s coastal environment.
- Operational readiness: inclusion of climbing steps, grounding, bird guards, and vibration dampers to support safe operation and maintenance.
Pricing & Quotation
SOLAR TODO offers three pricing tiers for this product line: FOB Supply (equipment ex-works China), CIF Delivered (including ocean freight and insurance), and EPC Turnkey (fully installed, commissioned, with 1-year warranty). Volume discounts are available for large-scale deployments. Configure your system online for an instant estimate, or request a custom quotation from our engineering team at cinn@solartodo.com.
Frequently Asked Questions
1) Why did SOLAR TODO use a steel tubular monopole instead of a lattice tower?
For this Colombo line, the project used steel tubular transmission poles (NOT lattice, NOT FRP) to simplify structural detailing and provide a consistent galvanization envelope on Q345 steel while meeting the required wind design basis under IEC 60826.
2) What wind conditions were the poles designed for?
The pole system was engineered for wind class 4 (40 m/s), aligned to IEC 60826 and supported by mechanical accessories such as vibration dampers.
3) What conductor and mechanical limits were considered for the 10kV line?
The project used ACSR 120 conductor with 470kg/km and max tension 38kN, combined with 0.8m phase spacing and 5m ground clearance to maintain safe electrical and mechanical performance.
4) How is the pole anchored to the foundation?
Each pole is supported by a spread_footing foundation with concrete and an anchor cage, and the steel pole uses flanged bolt sections to support controlled alignment and secure assembly.
References (Standards & Guidance)
- IEC 60826 — Overhead lines: wind load considerations for line design.
- GB 50545 — Code requirements for overhead line structures.
- IEEE Std 1133 — IEEE guide for overhead transmission line structures (general structural considerations).
- NREL / IRENA (grid reliability context) — published guidance on grid resilience planning (used to frame reliability outcomes for transmission upgrades).
- World Bank (infrastructure planning references) — guidance on resilient infrastructure implementation in developing/urban contexts.
For more details on the product configuration and engineering workflow, explore our Power Transmission Tower product page or contact us.
Equipment Deployed
- 261 × 25m tapered steel tubular transmission poles (NOT lattice, NOT FRP), hot-dip galvanized Q345 steel, ~25t/pole (1000kg/m), flanged bolt sections
- Cross-arm bracket system for insulator strings + ACSR conductors (10kV double-circuit), phase spacing 0.8m, ground clearance 5m, insulator length 0.5m
- Conductor specification: ACSR 120 (470kg/km, max tension 38kN) with vibration damper integration
- Accessories per pole: climbing steps, cross arm, grounding, bird guard, vibration damper
- Foundation system: spread_footing concrete foundation with anchor cage for monopole base