It's getting a little complex here because I'm not familiar with the grounding arrangements in South America, and there are different systems in use (e.g. there are differences between the U.S. and U.K.). I don't know whether Brazil follows American practice or European practice, or neither. (Anyone????)
Do you not have a grounding bar at your main distribution panel? Even if most or all wall outlets are 2-prong only, there may still be a ground connection at the panel.
