161kV Overhead Transmission Line Project in Ghana 

ZHM Metal Engineering Co., Ltd. has completed the design, fabrication, supply, and installation of a 161kV overhead transmission line (OHTL) in west Ghana Region. The project includes two line sections – Chirano (11.7 km) and Wassa (2.3 km) – located in the Western Region of Ghana, serving gold mine enclaves. 

161kV  Transmission Lines Distances and Connection Points

GP Substation Name ( New / Extension)	Corresponding  GRIDCo  161KV Substations	Approximate Length(km)  between Genser Sub and GRIDCo Sub
Wassa 161kV Substation(New)	Bogoso Substation- Wassa Akyepim Substation	2.3km
Chirano 161kV & 33KV Substation (New)	Asawinso Subsation- Juaboso Substation	11.7km

Efficient power transmission will be the determining factor in the seclection of the delectrical conductor. Service conditions establish a nominal load of site power plant condition: Each circuit is 161kV with 80MVA capacity each, total 160Mva.

In it’s route, there are angles of elevated value, close to 90degrees and two crossing of existing lines is also identified. OHTL lines begins and ends in the dead end towers.The lead-downs are outside of the scope of the present. The arrangements required for the final connection to the equipment at end end of the line. It’s proposed that the final lead-downs and connections between the overhead lines and switchgear at the substation will be provided by a three-core power cable, underground proposal. 

Project Scope at a Glance

☼Voltage level: 161kV double-circuit
☼Conductor: Twin-bundle ACSR 300/40 (Aluminium Conductor Steel Reinforced)
☼Earth wires: One galvanized steel earth wire (JLB40A-150, 40% IACS) + one OPGW-24B1-150 (24 fibres)
☼Tower type: Steel lattice self-standing towers, hot-dip galvanized
☼Insulators: 70kN / 100kN / 120kN disc suspension and composite types
☼Earthing system: Horizontal radial with galvanised round steel (D12) and copper-bonded rods

Steel Lattice Towers – Fabrication & Erection

All tower members were fabricated from high-strength structural steel (Grade 50 / ASTM A572) and hot-dip galvanised to BS EN ISO 1461. Each tower was delivered in sectional bundles via 20ft and 40ft containers to designated sites.

Erection method: Ground pre-assembly of sections using mobile cranes, followed by piecemeal lifting and bolt tightening. Bolts torque values were applied per diameter – e.g., M16 bolts at 80–90 N·m, M20 at 160 N·m. Anti-pilferage bolts were installed below 3m height. Tower plumb tolerance: ≤1/480 of height.

Foundation Works

Geotechnical investigations (Final Geotech Report, May 2024) indicated an allowable soil bearing capacity of 220 kPa. Foundation types included pad and chimney designs, with excavations by track-mounted drill rigs. Steel reinforcement cages and stub angles were positioned before concrete pouring (off-site batching or on-site mixing). Earthing trenches were excavated simultaneously – depth ≥0.6m (non-cultivated) or ≥0.8m (cultivated). Copper-bonded steel rods (5/8″ × 2.4m) and D12 galvanised round steel were used for the earthing grid.

Conductor & Earth Wire Stringing

Tension stringing method was applied to keep conductors off the ground during pulling. Snatch blocks (≥600mm pulley diameter, neoprene-lined) and hydraulic tensioners (bull wheel diameter ≥35× conductor OD) were employed.

Sag and tension followed equivalent span calculation, with creep compensation and pre-tensioning for 1 hour. Final sag tolerance: ±5% of design sag, and sag difference between phases ≤150mm.

Mid-span joints were avoided unless approved and located ≥25m from clamps, not crossing roads or live lines. Compression joints (hydraulic type) were used exclusively.

Insulator Strings & Fittings

❤Suspension strings: Single or double (for important crossings) using UB/ ZBS hanging plates, ball eye and socket couplings, and preformed suspension clamps (CL series).
❤Tension strings: U-shaped rings, extension rings, connecting plates, 100kN disc insulators, and hydraulic tension clamps (NY-300/40A).
❤Jumper strings: For angle towers, preformed suspension clamps with optional counterweights (FZC-10) to control wind deviation.
❤Earthing wire strings: Used UK-1290 hanging plates, parallel groove clamps (JB-3 for JLB40A-150), and grounding terminals.

All fittings complied with BS 3288, IEC 61284, and DIN/VDE 0212.

Earthing System

Based on soil resistivity varying between 100 Ω·m and 2000 Ω·m (conservative design used 1000–2000 Ω·m), the earthing system comprises:

❤Horizontal ring-radial electrodes (D12 galvanised round steel)
❤Copper-bonded steel rods at tower extremities
❤Connection to each tower leg using M16 bolts/nuts/washers
❤Measured power frequency resistance per tower as per project table

OPGW earthing at substation gantries used special tension strings with grounding lugs (JDBG-150 or JLO-16OPGW).

Crossings & Protective Measures

The route includes road crossings and two existing live line crossings. Scaffold and conductor support systems were designed to BS EN 12811-1, with earthed scaffolding (≤50 Ω) and anti-climbing devices. Clearance requirements followed the Electricity Safety (Electric Line Clearance) Regulations 2020.

Anti-Vibration Protection

Preformed vibration dampers were installed on both conductors and earth wires:

❤ACSR 300/40: FD-5 dampers, distance 0.8–1.2m from clamp, quantity based on span (2 sets for 101–250m, 4 for 251–500m, 6 for 501–750m).
❤JLB40A-150: FD-3 dampers, same spacing rules.
❤OPGW-24B1-150: 4D-30-16.5 dampers with preformed armour rods.

Quality & Standards Compliance

All works followed international standards including IEEE 524 (stringing), IEC 60826 (loading), BS 8004 (foundations), IEC 61284 (fittings), and IEEE 1048 (earthing). Each compression joint was tested and recorded by approved linesmen. Final inspection included tower footing resistance tests, sag verification, and bolt re-tightening after stringing.

Conclusion

ZHM Metal Engineering Co., Ltd. successfully delivered the complete 161kV OHTL for Chirano and Wassa – from foundation and earthing to tower erection, conductor stringing, and accessory installation. The project demonstrates our capability in turnkey overhead transmission line solutions under tropical conditions.

For commercial andtechnical inquiries or collaboration, please contact our engineering department.

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 Overhead Transmission Line OHTL ?

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

Would you like to see more information and images of ZHM Huawu Steel's Metal 161kV Overhead Transmission Line OHTL ? Visit our Photo Gallery.

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