ZHM Metal Successfully Completed Chirano & Wassa 161kV OHTL Project in Ghana

ZHM Metal Engineering Co., Ltd. is pleased to announce the successful completion of the detailed engineering, fabrication, supply, and on-site construction supervision for the Chirano and Wassa 161kV Overhead Transmission Line (OHTL) project in Ghana.   this critical infrastructure project spans a total of 14 kilometers (11.7km for Chirano and 2.3km for Wassa), providing reliable power transmission solutions for gold mining enclaves in the Western Region of Ghana.

This project showcases ZHM Metal’s comprehensive capabilities in delivering turnkey transmission line solutions, from structural design and galvanized steel fabrication to the installation of conductors, ground wires, and grounding systems.

Project Scope and Technical Overview

The Chirano & Wassa 161kV OHTL project involved the construction of double-circuit transmission lines utilizing robust Lattice Steel Towers. The route, characterized by angles nearing 90 degrees and several existing line crossings, required meticulous planning and adherence to international standards such as IEC 60652, ASCE 10-97, and DIN VDE 0210.

ZHM Metal was responsible for the full scope of works, including:

▷Route Survey and Site Preparation: Including vegetation clearance and access track construction.
▷Tower Foundation Works: Excavation, reinforcement, and concrete pouring.
▷Erection of Lattice Towers: Assembly and lifting of galvanized steel structures.
▷Stringing Works: Tension stringing of conductors and earth wires.

▷Final Testing and Inspection: Ensuring compliance with design specifications.

Comprehensive Product Line and Engineering Solutions

As the main subcontractor for design, engineering, fabrication, and supply, ZHM Metal delivered a full suite of transmission line materials, all of which have been successfully commissioned.

1. Steel Lattice Towers and Structural Components

The backbone of the project is the Hot-Dip Galvanized Steel Lattice Towers. Designed for a 1000m altitude and a basic wind speed of 27m/s, these self-supporting structures were fabricated using high-strength structural steel (Grade 50) compliant with ASTM A572 and ASTM A36.

Technical Highlights: The project utilized 8 different tower types, including suspension towers and strain towers capable of handling significant angular deviations. All bolts and nuts were secured with anti-pilferage features below 3 meters, and strict tolerances (1/480 of height for plumbness) were maintained during erection.

2. Conductors and Ground Wires (OPGW & GSW)

To ensure efficient power transmission and system reliability, ZHM Metal supplied and installed the following conductors and shielding wires:

▷Phase Conductors: Twin-bundle ACSR (Aluminum Conductor Steel Reinforced) cables, specifically 2XLGJ-300/40 (or JL/G3A-300/40), were installed with a horizontal spacing of 400mm. This configuration provides a high current-carrying capacity suitable for the 160MVA total load.

▷Ground Wires: A dual configuration was adopted, comprising an Aluminum Plated Steel Strand (JLB40A-150) and an OPGW (Optical Ground Wire) with 24 fibers (OPGW-24B1-150). The OPGW serves the dual purpose of lightning protection and telecommunications.

3. Insulator Strings and Fittings

A variety of high-voltage hardware was deployed to secure the conductors to the towers. This includes Disc Suspension Insulators (100kN and 120kN ratings), Tension Clamps, Suspension Clamps, and Ball & Socket Couplings.

Anti-Vibration Measures: To mitigate wind-induced vibrations, Preformed Vibration Dampers (FRY-3 for conductors and FRY-1 for ground wires) were installed at specified distances from the suspension clamps, ensuring the long-term integrity of the conductors.

4. Earthing and Grounding Systems

Given the high soil resistivity (estimated between 1000-2000 Ωm) in the region, a robust grounding system was essential for lightning protection.

Implementation: ZHM Metal installed a Horizontal Radial Grounding Device for each tower base. This system utilizes Copper-Bonded Steel Rods (5/8", 2.4m length) and Hot-Dip Galvanized Steel Wire (D12mm). The trench depth was maintained at a minimum of 60cm, and all welding joints were treated to prevent corrosion.

Stringent Quality Control and Installation Methodology

The successful execution of this project relied on a rigorous Method Statement that governed every phase of construction.

▷Foundation Construction: Drilling and concrete pouring were conducted according to geotechnical reports, with soil bearing capacity verified at 220kPa.
▷Tension Stringing: A key technical challenge was the "tension stringing" process. ZHM Metal employed a pilot wire system with Snatch Blocks and Tensioners to keep the conductors off the ground at all times, preventing damage such as "bird caging." Sags and tensions were meticulously measured using dynamometers and sighting boards to ensure accuracy within ±5%.

▷Safety and Compliance: The project adhered to strict safety protocols, including the use of scaffolding for live line crossings and comprehensive earthing of all temporary structures.

The completion of the Chirano and Wassa 161kV OHTL project marks a significant milestone in ZHM Metal’s international portfolio. By delivering a complete package of Transmission Line Towers, ACSR Conductors, OPGW Cables, and Grounding Materials, ZHM Metal has demonstrated its ability to handle complex EPC (Engineering, Procurement, and Construction) subcontracts in challenging environments.

This project not only provides essential power infrastructure for Ghana’s mining sector but also stands as a testament to ZHM Metal’s commitment to quality, safety, and technical excellence in the global power transmission industry.

1 Ghana 161kV OHTL Construction Method Statement

1A Angle strain Straight Alignment Tower Family Selection

2 Chirano Wassa Power Transmission Line Gold Mines

3 Scalfold Section Cross Over Existing 11kV ECG Tower Pylons

4 Scalffold Netting Over 11kV Crossing 35KV Catenary Wires

5 Lattice Angle Tower Concrete Rebar Schedule Foundation

6 Tower Foundation Excavation Pedestal Blinder reinforcement

7 Anchor Bolts Formworks Template Plate Rebars Pedestal RC Pouring

8 Foundation Formworks Disassembly Backfilling Plinth width Eccentricity Measurement

9 RC composition Ratio Gravel Mixing Testing Bock Vibration Plinth

10 Copper Bonded Steel Rod Earthing Trench Tower Foots

11 Wiring Rod Grounding Earthing Rod

12 Trench Depth Earthing Wire Rod Weld CADweld

13 Earthing Grounding Inpsection Testing

14 Latticed Angle Tower Products Packing Marking

15 Latticed Angle Tower Crossarms Products Packing Marking

16 Chirano OHTL 2D1 SJ1 21M Straight Alignment Towers

16 Conduct Cable Coil Shipment

17 Wassa OHTL Tower Container Loading Shipment

18 Lattice Tower Steel Structure Erection Drawing

20 Bottom Column Footing Brackets Mounting Anchor Bolts

21 Twin Bundle Conduct ACSR JL G3A 300 LGJ

21-Twin-Bundle-Conduct-ACSR-JL-G3A-300-LGJ

22 Crossarm Tip Conduct Insulator Hanging Plate

23 Tension strain String Twin Bundle Conduct Disc Suspension Insulator

24 Substation Gantry Structure String Tension Suspension T Connector

25 Angle Strain Jumping Conduct treatment

26 Straight alignment Latticed Self standing towers

27 Earthing Wire String Details Angle Strain Tower Gantry Earthing Wire

28 Tower Break In Tie In Solution T Connection Pai Existing Tower Terminal

29 Antivibration Damper Installation FD 4D 30 OPGW Earthing Wire

Why ZHM Huawu Metal 161kV OHTL Transmission Line Solutions?

Reliable and Customized Designs	Cutting Edge Designing Process	Free Online Price System	Easy Bolt-by-number Assembly
Over Two Decades of Experience	Value For Money	Unmatched in Quality and Craftmanship	Excellent Customer Service

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HOW CAN WE HELP YOU?

ZHM’s world-class team — together with our raw material suppliers and subcontractors — works to solve your most challenging design, engineering, farbrication or construction issues.

Contact ZHM by telephone at +86 135-8815-1981 (wechat and whatsapp) or send us your questions via email to info@zhmsteelworks.com