The Acaray Dam is a hydroelectric dam situated in Hernandarias, Paraguay. It has an electrical output of 210 megawatts (280,000 hp), supplying 3% of Paraguay's electricity demand.
The power plant's switchyard has a HVDC back-to-back station built by Siemens in 1981. It has a power rating of 55 megawatts (74,000 hp) and an operating voltage of 25 kV. It converts the electrical frequency from 50 hertz to 60 hertz to supply electricity to Brazil's power grid, which operates at 60 Hz (Paraguay's power grid operates at a frequency of 50 hertz).