What criteria define bidding-zone equivalents, and how does this apply in Brazil? 

Per Regulation 2019/943 (ISCC EU 202-6 Annex III), a bidding-zone equivalent requires either geographically differentiated, hourly-based electricity pricing or physically separate network subsystems; in Brazil, the National System Operator (ONS) treats its North, Northeast, South and Southeast–Midwest grids as separate subsystems equivalent to bidding zones.