Project Overview
Tanzania is endowed with abundant mineral resources, with copper-cobalt mining operations mainly concentrated in the Iringa, Mwanza, and Kagaduwa regions. A large copper-cobalt open-pit mine in the area was facing serious power supply issues due to its outdated power distribution system. The old transformers could no longer handle the high-intensity demands of mining equipment. The site operates under harsh conditions: year-round high temperatures, distinct wet and dry seasons, and heavy dust in the open-pit areas. The ore processing plant’s crushers and flotation machines generate significant impact loads, while the local public grid, supplied by TANESCO, suffers from pronounced voltage fluctuations and frequent instability. Diesel generator sets are often required to operate in parallel with the grid to supplement the supply. The project required a comprehensive upgrade and replacement of the existing transformers with reliable, high-performance units capable of withstanding extreme working conditions. The equipment also had to endure long-distance sea freight followed by rough overland transport within Africa. Since the mine is located in a remote area with long lead times for spare parts procurement, the new transformers had to be maintenance-free or require very little maintenance.
Solution
To address the specific challenges of this copper-cobalt mine, we provided a complete power supply upgrade solution centered on the S11-M series fully sealed oil-immersed power transformers. These are 10kV copper-wound transformers with a corrugated-tank fully sealed structure that completely isolates the internal components from sand, dust, and humid air. The breather is eliminated, fundamentally preventing failures caused by dust clogging. The technical specifications were tailored to the mine’s operational needs: frequency 50Hz, high voltage side 10±2×2.5kV with an off-circuit tap changer, low voltage side 0.4kV (single-phase 230V), and Dyn11 connection group, which effectively suppresses harmonics and suits the high-power impact loads typical of mining operations. The windings are made of high-purity oxygen-free copper, capable of withstanding frequent start-stop cycles and high short-circuit currents. The cooling method is oil-immersed self-cooling (ONAN). The fully sealed design enables long-term maintenance-free operation in remote mining areas, greatly reducing on-site inspection costs. Compared with the obsolete S9-type transformers that were previously used, the no-load losses are reduced by more than 30%, which lowers fuel consumption for the diesel generator sets and continuously cuts electricity costs at the mine site. The sealed tank has fewer welds and a lower risk of oil leakage, which is particularly important given the long procurement lead times for spare parts in African mining regions – this effectively prevents production losses due to downtime caused by oil leaks. The core structure is robust and the transformers were reinforced for container shipping to withstand the vibrations and impacts of long ocean voyages and rough inland transport. We provided end-to-end services covering manufacturing, anti-corrosion coating (compliant with ISO 12944 standards), packaging, sea freight to Dar es Salaam port, overland transportation, on-site installation guidance, and commissioning. Complete English technical documentation was supplied to meet all requirements for grid connection to the mine’s private power network, TBS-PVoC pre-shipment conformity verification, and customs clearance.
Client Feedback
The senior electrical engineer at the mine commented that before the transformer upgrade, equipment failures and power instability had been persistent problems that hampered production. After replacing the old units with the S11-M transformers supplied by our company, the operational situation improved dramatically. The fully sealed design has performed exceptionally well against the dust and humidity at the mining site – since installation, there have been zero failures related to environmental factors. The energy savings are substantial, and the maintenance burden has been significantly reduced, allowing the technical team to focus on core production activities. The engineer also expressed high appreciation for our seamless logistics support, from shipping to on-site commissioning. This cooperation has greatly enhanced the reliability of the mine’s power supply and provided a solid foundation for sustained and stable production.
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