South Africa's power utility Eskom has blamed incessant blackouts affecting the country on problems in Zambia.
Africa's second-largest economy after Nigeria has been plunged into darkness in recent weeks, experiencing daily load-shedding of at least six hours, which is regarded as the worst in the country's history.
Eskom says a major incident recently occurred in Zambia and caused a system disruption that affected four Southern African countries.
Zambia suffered a nationwide power outage last Saturday, resulting in increased frequency in power transmission between some networks that are interconnected in the region.
As more power flowed northwards, overloading saw network tripping between Zimbabwe and Zambia, followed by loss of connection between South Africa and Mozambique's Cahora Bassa hydropower plant from where South Africa imports some of its power.
"What we do know is that Zambia has experienced a blackout over the weekend and lost close to 2,000 megawatts. And as part of being an interconnected network, there were power swings observed between the Zambian and Zimbabwean networks," said Segomoco Scheppers, Eskom's group executive for transmission.
"Because power was now flowing north, essentially from South Africa through Zimbabwe and into Zambia, when the interconnector tripped between Zimbabwe and Zambia, it then had an impact of over frequency in the Zimbabwean network. Various transmission lines tripped in Zimbabwe leading to a number of generators also tripping in the Zimbabwean network."
Mr Scheppers was responding to an increased public outcry in South Africa late on Tuesday.
"If the frequency goes too high or low it may result in tripping. We have interconnections between South Africa, Botswana and Zimbabwe, and between Zimbabwe and Zambia. The incident was a culmination of a number of small incidents," he said.
"When the interconnector tripped it had an impact in Zimbabwe, leading to generators tripping. When this incident occurred we were already in stage two load-shedding and had a couple of incidents on our emergency reserves."
Cost of power loss
According to Business Unity South Africa (Busa), a private sector lobby, the electricity outages are costing the country an estimated $199 million daily.
Busa says the load-shedding is threatening the survival of many businesses and hurting the economy by plunging investor confidence to its lowest levels ever.
The power rationing in South Africa has led to calls for the resignation of Eskom's chief executive officer Andre de Ruyter.
But Mr De Reyter said on Tuesday that he does "not intend to resign of my own accord."
The power utility has had 11 acting and permanent CEOs in the past 12 years.
Busa argues that heads rolling at Eskom is not the solution as it "rejects these calls and stands with the Eskom leadership in these difficult times."
The group said South Africa's power shortages "lies in years of irreversible damage inflicted on the utility over more than a decade of state capture and corruption which resulted in critically under-maintained plants."