The technical defects of Brazil ±800 kV Xingu convertor station led to chain reaction on March 21

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2018. Widespread power outages affecting the entire country have had a significant impact in 14 northern and north-eastern Brazilian states. The general situation and the course of the accident of Brazilian power grid are introduced briefly in the paper. Furthermore

the main causes of the accident are analyzed in this article. On the basis of Brazilian blackout

Qishao DC transformation line is evaluated from the relay protection

configuration and strategy analysis of security and stability equipment

primary frequency regulation of power plants. Considering the actual condition of Hunan power grid

the lessons from Brazilian blackout on March 21

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are summarized.