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Sierra Leone

Bumbuna TL and Distribution System

Engineering for transmission and distribution system

Sierra Leone

Bumbuna Transmission line and Distribution system

The Bumbuna Hydroelectric Project (BHP) is the first power plant in the history of Sierra Leone and is of considerable importance as it produces more than 50% of the country’s total electricity.
The project site is located near the Bumbuna Falls on the upper reaches of the Seli/Rokel river, about 200 km northeast of the capital city, Freetown.

Main Project components are a hydroelectric generation scheme at Bumbuna Falls with a first phase installed capacity of 50 MW and a 161 kV transmission line, 205 km long, connecting the power station to Freetown. The project was carried out by Studio Pietrangeli for the Government as part of a programme to implement electricity transmission and distribution in all urban and rural areas of the country: the exploitation of its reservoir has led to a significant improvement in the national energy situation with a generating output of 50 MW in a country where the electricity supply – where present – was weak and inconsistent.

The project entails crucial contribution to Sierra Leone’s electrification and sustainable energy access thanks to the innovative design of the 161kV Bumbuna – Freetown transmission line. In fact, this high-voltage power line is provided with the Insulated Shield Wires Scheme (ISWS) conceived by Prof. F. Iliceto. The ISWS consists of insulating the shield wire(s) from the towers of the HV lines by means of insulators and energizing the wire(s) at MV (34.5 kV) from an interposing MV/MV transformer station at one end of the HV line. MV/LV transformers are connected between the shield wire(s) and ground for power supply to the loads, thus allowing to exploit the energy generated from Bumbuna HPP while supplying villages and towns along the transmission line route.

While the BHP helped to resolve the immediate supply shortages, a clear strategy is needed for the future expansion of power generation capability: the Bumbuna project can serve as a catalyst and model for the country to introduce it to sustainable development. Besides the additional cascade step development which will add 225MW to the existing 50MW of installed capacity, Bumbuna is becoming a key transmission system node due to the interconnection with the 1300km long, Cote d’Ivoire – Liberia – Sierra Leone – Guinea (CLSG) 225kV line, to be commissioned soon.

Sierra Leone


Ministry of Energy / Power – Government of Sierra Leone


2006 – 2009


Main Features

  • Transmission Line (L = 205 km, V = 161 kV)
  • Step-up Transformers (No.2, 33.7 MVA, 165/13.8 kV) in Bumbuna HPP station
  • Step-down Transformers in Freetown (No.2, Rated Voltage = 161/33/11.5 kV)
  • Interposing Transformer in Bumbuna (Rated Voltage = 13.8/34.5 kV)
  • Step-down Transformer in Makeni (Rated Voltage = 34.5/11 kV)
  • Pole Transformers (Rated Voltage = 34.5 /0.415 kV)
  • Shield Wire Scheme (34.5 kV)

Sierra Leone

Bumbuna Transmission line and Distribution system


Feasibility Study

Preliminary Design

Network stability studies upon request of the World Bank (1991 and 1996)

Tender Documents

Final Design

Master Plan update

Supervision of works

Supervision of the Operations and Maintenance contract of the “ad-interim” Operator

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