On December 15, at 5:55 pm, occurred the automatic shutdown of five of the six generating units in operation at Itumbiara plant due to electromagnetic interference in the protection circuit.

As a result of these shutdowns, responsible for the rejection of 1,025 MW of load in the BIPS, by setting due to the busbar physical arrangement, type "modified ring ", in Itumbiara plant substation, at 500 kV TL Emborcação - Itumbiara, in this terminal, and local AT53, 500/345/13,8 kV autotransformers bank, 500 kV side, were off simultaneously.

The severity of the disturbance resulted in the loss of synchronism between systems Acre / Rondônia and North / Northeast / Midwest, and the latter with the South / Southeast.As a consequence, 230 kV, 345 kV and 500 kV trunks circuits were disconnected by remote tripping and tripping for sync loss, due to electromechanical instability checked, which was more pronounced in Minas Gerais.In addition to the transmission lines, generating units of various hydraulic and thermal power plants in the BIPS were also switched off.

Main actions and measures implemented:

• Furnas is implementing improvements in shielding the control circuit of electric protections of generating units of Itumbiara plant, which prevents the penetration of outbreaks in the substation, and performances undue protections.
• A working group involving experts from ONS, Cepel and agents was constituted to verify weaknesses in the engineering of the BIPS substations considered strategic for the operation, with the aim of proposing configuration, physical or equipment adjustments in order to ensure greater operational reliability to these facilities and the BIPS.