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Setor Elétrico
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Entry · Operation

Isolated Systems

Which distribution systems are not connected to the interconnected system?

● checked against the primary source on Oct 9, 2026Source: Presidency of the Republic and ONS

Acronyms: ONS, National Electric System Operator; PASI, Isolated Systems Monitoring and Information Portal, from the EPE; EPE, Energy Research Office; ANEEL, Brazilian Electricity Regulatory Agency.

In one sentence

Public service electricity distribution systems that, in their normal configuration, are not electrically connected to the National Interconnected System (SIN), for technical or economic reasons.

Real example

Population of the localities served by isolated systems

1,964,825peopleNature of the data: Observed

2025 · Brazil, isolated systems

Source: EPE, PASI: Localização Geográfica das localidades isoladas. Reference up to 2025. Captured on Sep 30, 2026.

Population of the isolated system localities that the EPE lists in the most recent PASI cycle, reported by the distribution utilities; a locality without reported population is excluded from the sum.

See in the panel: Inclusion: isolated systems

Observed: Value published directly by the official or primary source.

Why it matters

A SIN value describes the interconnected system: the localities served by Isolated Systems are outside it, by definition. The ONS page says that consumption in them represents less than 1% of the country's total load, without a reference date, and that demand is met mainly by diesel thermal plants. The Energy inclusion panel lists the localities and the population of the PASI, from the EPE.

Not to be confused with

  • SIN (National Interconnected System)

    According to the ONS, the SIN is the group of four subsystems: South, Southeast/Center-West, Northeast and most of the North region. Isolated Systems are distribution systems that, in their normal configuration, are not connected to the SIN. A SIN value does not describe the localities served by Isolated Systems.

What cannot be concluded

  • The ONS page on isolated systems gives no reference date for the count of localities, for their share of the load or for the list of capitals served: the entry cites it as written and does not use these figures as observatory data.
  • The decree read is the consolidated text from Planalto, with the wording of Decree No. 11.629 of 2023 in the item that defines Isolated Systems; ANEEL acts on these systems were not read.

Related entries

Official source

  • Presidency of the RepublicDecree No. 7.246 of Jul 28, 2010, art. 2, item III (consolidated text published by Planalto, read on Oct 9, 2026) 

    In other words: the decree calls Isolated Systems the public service distribution electrical systems that, in their normal configuration, are not electrically connected to the SIN, for technical or economic reasons.

    Literal excerpt from the document
    Portuguese only“III - Sistemas Isolados - os sistemas elétricos de serviço público de distribuição de energia elétrica que, em sua configuração normal, não estejam eletricamente conectados ao Sistema Interligado Nacional - SIN, por razões técnicas ou econômicas;”

  • Presidency of the RepublicLaw No. 9.648 of May 27, 1998, art. 13 (consolidated text published by Planalto, read on Oct 9, 2026) 

    In other words: load forecasting and operation planning of the Isolated System are the responsibility of the ONS, from May 1, 2017.

    Literal excerpt from the document
    Portuguese only“e as atividades de previsão de carga e planejamento da operação do Sistema Isolado (Sisol) serão executadas, mediante autorização do poder concedente, pelo Operador Nacional do Sistema Elétrico (ONS) [...] g) a partir de 1º de maio de 2017, a previsão de carga e o planejamento da operação do Sisol.”

  • ONSONS, institutional page “O Sistema Interligado Nacional” (page without publication date, read on Oct 9, 2026) 

    In other words: the ONS describes the SIN as the group of four subsystems, the three of the South, Southeast/Center-West and Northeast regions and most of the North.

    Literal excerpt from the document
    Portuguese only“O Sistema Interligado Nacional é constituído por quatro subsistemas: Sul, Sudeste/Centro-Oeste, Nordeste e a maior parte da região Norte.”

  • ONSONS, institutional page “Sistemas Isolados” (page without publication date, read on Oct 9, 2026) 

    In other words: the ONS page, without a reference date, counts the isolated localities, places most of them in the North region, says that consumption in them is low (less than 1% of the country's total load) and that demand is met mainly by diesel thermal plants.

    Literal excerpt from the document
    Portuguese only“Atualmente, existem 212 localidades isoladas no Brasil. A maior parte está na região Norte, nos estados de Rondônia, Acre, Amazonas, Roraima, Amapá e Pará. A ilha de Fernando de Noronha, em Pernambuco, e algumas localidades de Mato Grosso completam a lista. [...] O consumo nessas localidades é baixo e representa menos de 1% da carga total do país. A demanda por energia dessas regiões é suprida, principalmente, por térmicas a óleo diesel.”

Documents accessed and text checked on Oct 9, 2026.

Check details

What the check found in the source
  • The definition comes from the decree; the scope of the SIN and that of the isolated localities come from ONS pages read on Oct 9, 2026, without a publication date.
  • The versioned capture of each document, with the sha256 of the original and of the text, is in the manifest of the Learn documents folder of Oct 9, 2026.