Minera Centinela said it had sold Centinela Transmission SA to Red Eléctrica Chile SpA.
Minera Centinela had created the subsidiary in November 2016, to facilitate the sale of the company that holds the three transmission lines totalling 265km that feed the copper mine in Chile.
The company noted Antofagasta had already sold its stakes in the Javiera photovoltaic plant and the Alto Maipo hydroelectric power station.
Antofagasta CEO Ivan Arriagada said the sale was consistent with the group's strategy of disposing of its water and energy assets.
"This allows us to focus on our core business of producing copper safely and profitably, while also taking advantage of any organic growth opportunities that may arise," he said.
At the company's AGM in May, chairman Jean-Paul Luksic said the outlook for copper looked positive and the company was examining expansion options for Los Pelambres and Centinela.
Shares in the company closed down slightly, by 0.3%, on Friday in London.
