Chimuara, Zambézia Province, Mozambique, Africa
The first of its kind in Mozambique, the Chimuara – Nacala 400 kV Overhead Transmission Line aims to meet the power demands of continuously growing industries and residential areas in Northern Mozambique. The region currently suffers from serious power cuts and shortages, and it is supplied by a limited 220 kV system that cannot sustain future growth.
The new 400 kV system will be supplied from two existing 220 kV circuits originating in the Tete area. The project’s 400 kV system will raise both the thermal and stability limits of the network’s power transfer capability, improving both availability and reliability. In the future a 400 kV backbone system will be developed. Moreover, the system will allow for flexible future dispatch of power from any future power plant that may be developed in the north eastern part of the region.
The project has exceptional social value, as it promises to put local people to work, expand the electrical grid into rural communities, and promote commercial and/or industrial investments.
The venture includes the construction of a 367-km single circuit 400 kV overhead transmission line, which forms EDM’s first 400 kV project in Mozambique.
The project also includes the construction of one new 400/220 kV substation in Chimuara as well as the upgrade of the existing 220/110 kV Alto Molócue substation into a 400/220/110 kV substation. Both of these substations will be interconnected by the 367-km 400 kV transmission line.
To support this essential project, Dar provided extensive project management and value engineering services. Working with EDM, Dar strived to optimise project cost, while maintaining quality standards.
For example, Dar supported EDM in revisiting the 400 kV conductor selection process by presenting the advantages and disadvantages of various alternatives. EDM then approved the use of low loss aluminium conductor steel reinforced trapezoidal shape conductors, a class of conductors that offers long-term financial savings thanks to reduced heat losses as compared to conventional stranded type ACSR conductors.
Dar also suggested and implemented the European Norms EN 50341-1 and EN 50341-3-17 for the entire overhead system. These codes enable the well-integrated and optimised design of the steel towers. The integrity of the design of each tower is then verified at the tower’s testing stations during the load testing.
EDM and Dar also discussed pivotal value engineering ideas for the substations. One such idea was for the substations’ busbar configuration. It was agreed that the original concept of the high-cost double-breaker double-busbar scheme would be modified into a single-breaker double-busbar scheme, equipped with bypass switches for the line bays, thereby ensuring that failure of any given line breaker may be substituted by the coupler breaker with no disruption to the substation service. This modification not only resulted in significant savings in substation equipment cost but also yielded space and land savings.
Due to these efforts and various others, the final project cost came in at approximately $40 million under the proposed budget – money Mozambique could put right back into its communities and which will help EDM pursue additional projects and make further expansions.