Around 14 GW of irregular distributed solar threatens grid security in Brazil, warns TÜV Rheinland

The undeclared expansion of distributed solar photovoltaic generation has evolved from a regulatory issue into a matter requiring greater attention in the planning and operation of Brazil’s electricity system, while also increasing technical risks at individual installations, according to Vinicius Gibrail, director of the Solar and Commercial Products Division at TÜV Rheinland in South America.

The issue is central to Public Consultation 009/2026 by the National Electric Energy Agency (Aneel), which proposes regulatory measures to address surplus energy and increase operational flexibility within distribution networks. Among the proposed measures is a crackdown on unauthorized changes to the original specifications of micro- and mini-distributed generation (MMGD) systems, which in Brazil include all PV installations not exceeding 5 MW in size.

The consultation is based on Technical Note No. 148/2025-STD/Aneel, which documents reports from distribution companies of unauthorized increases in MMGD capacity, as well as warnings from the National Electric System Operator (ONS) about the impact of distributed generation on the operation of the National Interconnected System (SIN).

According to ONS estimates cited in the regulatory process, unauthorized additional capacity could reach 14 GW. The figure represents distributed generation capacity that is not adequately reflected in official records.

“Failure to notify Aneel of expansions—whether by an individual or a company—keeps the additional capacity hidden. This is not only illegal but also imposes additional costs on other consumers, similar to traditional energy theft,” Gibrail said.

System impact

Undeclared generation can widen the gap between the capacity actually connected to the grid and the capacity recorded in databases used by distribution companies and the ONS.

“Since this energy is not registered, the ONS does not factor it into its projections and operational decisions,” Gibrail said.

Technical Note 148/2025-STD/Aneel links unauthorized system expansions to the management of surplus energy within distribution networks. However, this does not mean irregular generation is solely responsible for curtailment. Rather, the core issue is the increased uncertainty over the actual amount of generation available at a given time.

Safety risks

Beyond their impact on system planning and operation, expansions carried out without a design review can compromise the electrical safety of individual installations.

“Generation systems must adhere to the standards set by the Brazilian Association of Technical Standards (ABNT). Installations must comply with ABNT NBR 16690:2019—which establishes design requirements for photovoltaic array installations—and NBR 5410, which covers low-voltage electrical installations, to ensure safety and proper operation,” Gibrail said.

According to Gibrail, projects should also involve a qualified professional registered with the Regional Council of Engineering and Agronomy (CREA), with the corresponding Technical Responsibility Annotation (ART) issued.

He also emphasized the importance of using equipment that complies with applicable technical standards, including PV modules, inverters, and protection devices.

“Solar energy generation enables Brazil to maintain a clean energy matrix that fosters economic development. However, for this process to occur safely, projects must be properly regularized, technical certifications must be met, and certified equipment must be used,” Gibrail said.