Brazil, ONS

Power system main characteristics

The Brazilian Interconnected Power System is a multi-owned hydrothermal system with an installed capacity of 122,100 MW, which supplies an energy market of 541 TWh, with a peak demand reaching 85.7 GW (2014 figures).

Hydro generation is dominant, accounting for 72.4% of the installed capacity. Non-conventional renewable generation – wind and sugarcane bagasse – raise the proportion of clean energy in the system to 81.6%.

The transmission grid has an extension of 125,600 km of lines at voltages of 230 kV and above. Long distance lines connect far away generation to the major load centers near the coast and interconnect geographical regions and river basins, thus allowing safety of supply and optimization in the use of the available resources.

ONS – Operador Nacional do Sistema Elétrico – is a private non-profit organization, responsible for the operation of the generation plants and the transmission grid. Without having the ownership of any asset in the system, ONS takes decisions aiming at a reliable power supply, at minimum cost.

Major incidents & preventive measures

The energy shortage

From June’2001 to February’2002, the Brazilian consumers faced an energy rationing, in which their consumption had to be voluntarily reduced by 20%, as a consequence of low inflows and delays of expansion plans.

After that episode, ONS improved its operations planning procedures in order to increase the preventive dispatch of thermal generation, in addition to what is recommended by optimization models. On the other hand, the government created the Power Sector Monitoring Committee, with the objective of analyzing permanently power supply conditions in the country.

The power blackouts

The most recent large disturbance in Brazil occurred on February 4th, 2011. It started in the Northeastern region and was provoked by the accidental operation of one breaker failure protection. During the restoration process, a new accidental failure occurred and disconnected one important substation, with the opening of several 500 kV transmission lines. This started an oscillatory process leading to the disconnection of 83% of the Northeastern load (7400 MW). A complete separation between this region and the Northern and the Southeastern regions also occurred. 40 million consumers in eight states were affected for 3.3 hours.

Since this disturbance ONS has reinforced several measures to minimize the occurrence of blackouts, to reduce their impact and to speed up the load restoration process.

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