ONS Activates Emergency Curtailment Plan and Cuts About 1,000 MW of Distributed Generation

Overview

• The Operador Nacional do Sistema Elétrico (ONS) used the Aneel‑approved emergency plan for the first time on the weekend to manage roughly 1,000 megawatts between 10:00 and 14:00 by coordinating central‑plant reductions and ordering distributors to cut small generators.
• Distributors executed curtailments of 'Tipo III' plants—small hydropower, biomass and small wind and solar units—that sit on distribution networks and are not directly dispatchable by the ONS.
• Twelve distribution companies were authorized to carry out the cuts and together cover about 80% of Tipo III capacity, with Abradee saying distributors followed ONS parameters while asking for clearer procedures and impact studies.
• The trigger was very high rooftop solar output combined with low demand during the long weekend, a pattern that risks flow reversal at substations and loss of system inertia needed to control frequency and voltage.
• The action forces near‑term oversight: ONS must file a technical report to Aneel within 30 days and the episode is likely to speed regulatory, incentive and operational changes as MMGD capacity, now near 43 GW, grows toward projections around 60 GW by 2030.