KETRACO Energizes 400/220kV Mariakani Substation, Strengthening Coastal Power Supply

Last Updated 4 days ago by Kenya Engineer

Kenya Electricity Transmission Company (KETRACO) has successfully energized the 400/220kV Mariakani Substation, marking a major milestone in the upgrade of Kenya’s high-voltage transmission infrastructure and significantly enhancing power reliability along the Coast region.

Located in Mariakani, Kilifi County, the substation forms a critical node on the Mombasa–Nairobi transmission corridor, acting as a power gateway between the Coast and the national grid. Its commissioning is expected to stabilize electricity supply for residential consumers, commercial facilities, tourism establishments, and both small- and large-scale manufacturing industries that have long struggled with voltage instability and frequent outages.

Backbone of the 400kV Mombasa–Nairobi Transmission Line

The Mariakani facility is a key component of the 400kV Mombasa–Nairobi Transmission Line, a strategic project designed to transmit over 1,000MW of electricity between the Coast and inland regions. By upgrading the transmission voltage from 220kV to 400kV, the project significantly increases power transfer capacity while reducing technical losses across the network.

With the Mariakani substation now energized, the Coast region is fully integrated into Kenya’s high-capacity transmission backbone, easing congestion on the existing network and improving overall system stability.

Enabling Regional Power Interconnection and Clean Energy Integration

The 400/220kV Mariakani Substation also strengthens Kenya’s role within the regional interconnected power system. Its commissioning enhances the operational effectiveness of major cross-border interconnectors, including the 500kV Ethiopia–Kenya HVDC link and the 400kV Kenya–Tanzania interconnector.

From an energy transition perspective, the project supports Kenya’s target of achieving 100 per cent clean energy by 2030. The upgraded transmission capacity allows greater dispatch of low-carbon electricity from key generation sources such as Olkaria geothermal fields, Lake Turkana Wind Power Plant, and hydropower imports from Ethiopia to the Coast—reducing reliance on expensive and polluting diesel-powered generation, particularly during peak demand periods.

Project Financing and Implementation

The Mariakani Substation was developed at a cost of approximately KES 3 billion, financed jointly by the Government of Kenya and the African Development Bank (AfDB). The project was implemented by China CAMC Engineering Co. Ltd, with supervision by KETRACO’s in-house engineering teams.

AfDB is also the lead financier for the associated transmission infrastructure, including:

The 400kV double-circuit Isinya–Mariakani transmission line
The 220kV double-circuit Mariakani–Rabai line

Completion of Phase II of the Mombasa–Nairobi Project

The energization of Mariakani completes Phase II of the Mombasa–Nairobi Transmission Line Project, which focused on constructing the 400/220kV Mariakani and Isinya substations and upgrading transmission capacity between them.

Phase I of the project involved the construction of a 492km double-circuit transmission line linking Rabai Substation at the Coast to Embakasi Substation in Nairobi, via Mariakani, Isinya, and Athi River. This phase included a technically complex 6.7km 220kV underground cable section through Nairobi National Park and was commissioned at 220kV in 2017 at a cost of KES 17 billion, financed by AfDB, the European Investment Bank (EIB), the French Development Agency (AFD), and the Government of Kenya.

With Isinya Substation completed in 2022 and Mariakani now energized, the full 400kV corridor between Mombasa and Nairobi is operational. Phase II was implemented at a cost of KES 7 billion.

Impact on Grid Reliability and Power Costs

According to KETRACO, the completed project will:

Increase transmission capacity to the Coast to over 1,000MW
Reduce technical power losses, lowering the overall cost of electricity
Improve voltage stability and power quality
Enhance grid reliability for industrial and commercial users
Support long-term economic growth in the Coastal region

The Mariakani Substation therefore represents a significant step toward a modern, resilient, and low-carbon national transmission grid, aligned with Kenya’s industrialization and energy transition goals.