Kenya Power staff at work. The utility firm has confirmed that collapsed towers along a high-voltage transmission line caused the power outage.
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Explainer: How one transmission line plunged country into blackout
What you need to know:
- Kenya’s electricity generation, transmission and distribution network is built like a stack of crates.
- In 2016, a monkey trip caused a countrywide outage, putting Kenya on international headlines.
Just how did the entire nation plunge into darkness following the collapse of only one transmission line out of many others that crisscross the country?
The high voltage Kiambere – Embakasi transmission line that collapsed at Imara Daima in Nairobi evacuates power from the 168-megawatt, KenGen-owned Kiambere Hydropower Station that is part of the Seven Forks hydropower stations located along the Tana River.
Indeed, the power plant that feeds the line is not even the largest in the country.
But on Tuesday at about 10.45am, the entire country was hit by a massive power outage that lasted hours after four towers supporting the line caved in.
Kiambere Dam is the second-largest reservoir along the Tana River – behind the 225MW Gitaru Dam – and is also dwarfed by other geothermal and wind power plants.
Power supply system
But Kenya’s electricity generation, transmission and distribution network is built like a stack of crates, such that displacing one sets off a chain reaction that collapses the entire pile.
When the line fell, it essentially cut off supply from the power plant, leaving the nationwide grid heavily imbalanced.
This means that while power demand was the same that morning, supply had fallen by a massive 168MW, a shortfall that caused a massive imbalance that the grid could not handle.
If a power plant is large, like Kiambere is, the grid cannot counterbalance its sudden elimination, as it would had it been a smaller plants of, for instance, a capacity of just 500 kilowatts (kW).
The imbalance causes the whole power supply system to trip and effectively shuts out other plants.
Countrywide outage
In 2016 for instance, a monkey trip caused a countrywide outage, putting Kenya on international headlines.
The animal fell on a power generator at the Gitaru Dam, which took the plant off the grid and set off a domino effect similar to that witnessed on Tuesday.
When such incidents happen, Kenya Power says it has to delicately switch on parts of the grid incrementally, one area at a time, to fully restore the national grid balance.
On Tuesday the firm used its SCADA (supervisory control and data acquisition) automation control system to remotely re-route the power generated from Kiambere to other transmission lines.
It started by restoring power supply to Nairobi, West Kenya, Mt Kenya, North Rift, South Nyanza and Central Rift before switching on other areas.
