Project Introduction and Scope of Supply

To achieve smooth transitions between different voltage levels, we designed a “three-tier cascaded” supply list:

A. Core Hub Layer

• equipment:Two 220kV/110kV 150MVA three-phase oil-immersed power transformers
• Quantity logic: 1 in use, 1 in reserve (N-1 principle) to ensure the absolute security of the main network.

B. Regional Allocation Layer

• equipment:Three 110kV/60kV 60MVA double-winding on-load tap-changing power transformers
• Role: “Bridge”. Connects the new 110kV ring network with the existing 60kV power grid in Rwanda’s old city, resolving the incompatibility issue between the old and new power grid systems.
• Quantitative logic: 2 operational units and 1 backup unit to cope with the heavy load in the core urban area.

C. Urban distribution layer

• equipment:Four 60kV/15kV 50MVA oil-immersed power transformers
• Role: “Distributor”. Reduces 60kV power to 15kV (Angola’s standard distribution voltage) and supplies it directly to municipal and industrial users.
• Quantity logic: Corresponds to 4 main urban power supply busbars, operating independently.

D. Terminal and Control Layer

• Distribution transformer:300 15kV/0.4kV 630kVA pole-mounted transformers (to supply power to surrounding residential areas).
• Complete set of equipment:

• 110kV GIS switchgear bay (with high-voltage side).
• 80 KYN61-40.5 (60kV side) and KYN28-17.5 (15kV side) metal armored switchgear .

C.”Forced Oil Air Cooling (OFAF)” Logic (to cope with equatorial high temperatures):

• For large transformers of 150MVA and 60MVA, natural cooling cannot meet the ambient temperature of 45°C in Angola.
• Principle: We have configured a dual-power redundant submersible pump and a powerful fan, and the PLC automatically controls the start and stop based on the top oil temperature to ensure that the temperature rise does not exceed 55K under full load.

Market research and product feature insights in Angola

We conducted in-depth research in the Luanda and Huambo areas and identified the following pain points, which we then translated into product features:

• The historical baggage of voltage standards: Angola’s power grid is a mixture of the old Portuguese standard (60kV) and the new international standard (110kV/220kV). KRON’s product design precisely matches this special 60kV voltage level, rather than simply applying China’s 66kV standard, ensuring accurate impedance matching and relay protection.
• Maintenance difficulties: There is a severe shortage of dry air generators and oil filters in the area. Therefore, all our large transformers are equipped with capsule oil conservators (MDTs) and maintenance-free dehumidifiers to ensure physical isolation between transformer oil and air, eliminating the need for on-site oil filtration for 10 years of operation.
• High humidity and mold corrosion: Designed for tropical rainforest climates, all secondary wiring terminals of the complete set of equipment are tin-plated and coated with three-proof paint (moisture-proof, mildew-proof, and salt spray-proof). The cabinet is made of aluminum-zinc coated plate, which has five times the rust resistance of ordinary cold-rolled steel plate .

Understanding Standards and Technical Requirements

• IEC 60076 (Power Transformers): Our design calculations fully comply with IEC standards and are KEMA certified.
• Angola Grid Code: We paid special attention to frequency tolerance . Due to the large proportion of hydropower in Angola, the grid frequency fluctuates greatly during the dry season (48.5Hz – 51.5Hz). Our core flux density design has a 10% margin to prevent oversaturation and overheating of the core during low-frequency operation.
• Noise control: Although it is an industrial station, considering its proximity to residential areas, we have kept the noise of the 150MVA main transformer below 65dB (better than the IEC standard of 72dB).

Product Advantages and Selling Points

• Full voltage level coverage capability: Very few manufacturers can deliver high-quality equipment at three high voltage levels—220kV, 110kV, and 60kV—in a single contract. KeRun demonstrates its integrated manufacturing capabilities across the entire industry chain.
• Extremely strong short-circuit withstand capability: In view of the frequent tripping of the Angolan power grid, we adopted self-adhesive transposition conductors in the manufacturing of transformer windings and carried out constant voltage drying to ensure that the coils remain “unmoved” under short-circuit electrodynamic forces.
• Intelligent Human-Machine Interface (Portuguese HMI): All control panels for complete sets of equipment and instructions for transformer temperature controllers are customized in Portuguese , which greatly reduces the error rate of local operators.

Procurement Considerations (Ironclad Business Rules)

Given the financial scale and logistical challenges of large-scale power projects, our business terms are rigorous and transparent:

• Trade terms: EXW or FOB.

• Note: A 150MVA transformer weighs over 100 tons. We are responsible for professional heavy-duty packaging and inland transportation to Chinese ports. Customs clearance in Angola and special transportation from Luanda Port to the project site (including bridge load-bearing assessment) shall be the responsibility of the buyer or its designated local logistics provider .
  • Payment terms: 100% T/T settlement before shipment.
• Note: This is international practice for large-scale customized equipment. We welcome RNT/ENDE of Angola to appoint a third-party inspection agency (such as SGS) to conduct FAT (Factory Acceptance Testing) in China. After the test is passed and a report is issued, the customer pays the balance, and we arrange shipment immediately.

Why do African countries choose KeRun Intelligent Control ?

• Exporting China’s infrastructure experience: We don’t just sell equipment; we export the experience accumulated in the process of China’s power grid transforming from “weak” to “strong.” Our equipment is more robust than European and American brands and is better suited to the power grid environments of developing countries.
• Rapid Response: Given the complexity of this equipment combination, Siemens’ delivery time could be as long as 14 months , but KeRun promises… It will be ready for delivery within 1-3 months , helping the Angolan government to bring electricity to people’s livelihood projects as soon as possible .