A document sent by Ghana’s power transmission company, GRIDCo, to the power sector players intercepted by Energynewsafrica.com indicates that the recent power outages experienced by electricity consumers in the West African nation was as a result of disturbances in the power system and not load shedding as was speculated.
The document detailed how power distribution difficulties occurred throughout the country in the last one week.
The report outlined a brief sequence of how the incidence occured, interventions and recommendations made to avert future problems to power consumers.
It explained that at 0:149 on Wednesday, August 26, 2020, the 330kV line circuit from Aboadze to Anwomaso, together with the Aboadze-Volta -Asogli-Davie 330 kV line circuit, the Ghana-Cote d’ivoire 225 kV interconnection, that of the Aboadze-Tokoradi 161 kV line No.1 and the 69kV Asiekpe were affected.
Additionally, the document observed that Ho and the 69 kV Asiekpe- Sogakope lines equally tripped, resulting in the unfortunate power outages in certain parts of the the country.
“All twenty-five units at Karpower, the Bui GS unit No.2 and Sunon Asogli unit no.9 and 10 also tripped, leading to a total loss of 750MW of generation,” the document stated.
It said, Automatic Frequency Load Shedding (AFLS) relays operated is ready to take off supply to some customers in Accra, Winneba, Cape Coast, Takoradi, Kumasi, the Volta Region and VALCO.
“Restoration started promptly and customer loads were restored pregressively as generation was re-synchronised to the NITS, and by 0:305h, power supply to all customers in Ghana will have been restored when supply is restored to Sogakope.”
The report mentioned, however that at 0:900h, another disturbance occured when a charcoal truck run into the Tafo-Akwatia 161kV line tower, snapping the line conductor and causing major damage to the line.
This, it stressed, required the engagement of a contractor to create access to the faulted pointed to enable the repair of the line.
“The outage to the Tafo-Akwatia line has caused a number of repeated disturbances over the week,” the document stated.
Intervention outlined by the report said a seven-day programme to wash the entire Tokoradi thermal substation had been initiated, engagement of a contractor to create access route and repair by September 11, 2020 had been undertaken.
It concluded that checks revealed excessive early morning dew on post insulators at the 330kV Takoradi Thermal substation caused a flashover, triggering cascaded trips in the 330kV line circuit, leading to the system disturbance.
It added that, the fault on one of the post insulators, supporting the Aboadze-Volta and Aboadze- Anwomaso 330 kV lines resulted in the disturbance.
The document recommended that due to closeness of the Takoradi Thermal substation to the sea, and consequential heavy deposit of salty dew at dawn especially in the rainy season, the following recommendations have been made: there is a short term to intensify regular washing of the Takoradi Thermal substation, coating of existing insulators with silicon coating.
In the medium term, the document called for replacement of existing ‘Glass’ and Porclain’ type insulation currently in use at the Takoradi Thermal substation with the polymer type.
In the long term, the document called for conversion of the Takoradi Thernal substation to a Gas insulated Substation (GIS), which is estimated to cost approximately 80 USD.