Arcing in high-voltage substations triggered by high humidity behind blackout (STEG CEO)

"The initial cause of the recent blackout was arcing in high-voltage substations at Radés power plant triggered by an exceptionally high humidity level (90%)," CEO of the Tunisian Company of Electricity and Gas (French: STEG) Hichem Anane Thursday said in an interview with TAP.

"STEG teams relied on the Algerian grid connected to Tunisia's to gradually restart national facilities," he added

Late on Tuesday night, a general power outage at 1:30 AM plunged Tunisia into total darkness. Despite official statements citing technical reasons, the disruption ignited a heated debate on social media.

The priority immediately after the outage was to restore power. Teams deployed across the country then started collecting data to identify causes, the CEO said.

The preliminary findings showed the initial cause was arcing in high-volage substations in Radés power plant; this was the result of a high level of humidity, attaining 90%.

This arcing caused the automatic shutdown of the three power plants in Radés, leading to a loss of about 875 megawatts (MW) amid an overall demand of 3,226 MW.

The automatic system defence plan to offset the loss was triggered but the capacity of other plants (Sousse, Gabès …) was exceeded, considering the short time between the failure and the outage ( 4 seconds).

A preliminary report supported by recordings, photos and technical data will be made available shortly.

Asked by TAP journalist if Tunisia's energy deficit accounts for its fragile electric system, the CEO said the blackout occurred at a time when the overall demand reached 3,226 MW while the production capacity stood at 5,400 MW.

The cut has nothing to do with the capacity of production. Theoretically, the installed production capacity meets Tunisia's needs but does not allow it to address peak demand.

Additional needs are today met through import contracts with Algeria, pending the development of programmes to expand the capacity of national power plants and a better integration of renewables.

Such incidents took place in other countries, such as France and Italy. Electric systems, mainly high voltage aerial lines, are vulenerable to climate fluctuations, including humidity. This justifies the approach adopted by the STEG to acquire shielded substations in the future.

Tunisia relied in its undertaking to restore power on the Algerian network (600 to 800 MW) and Libya's (50 MW). A better interlinking would strengthen the capacity of these countries to adress possible failures.

Additionally, ELMED, an energy bridge between Tunisia and Italy, will increase the country's electricity security, the CEO highlighted.