Comment Re:View from a US citizen living in Brazil. (Score 1) 359
Yes, this certainly sounds like a classis under-frequency event caused by the unexpected loss of a generator station. When you have unexpected loss of a station or a transmission line, the frequency on the grid can drop precipitously. Key to frequency is that every (conventional) power plant provides some level of frequency response built-in, while operating under Automatic Governor Control (AGC).
Other power plants under AGC are supposed to put the breaks on an uncontrolled voltage drop. Sounds like the system wasn't able to recover in this case -- either because there weren't enough other plants online to absorb the frequency deviation, or the backup plants that should have been ready to respond weren't quite so ready after all. Here's a link to the National Electric Reliability Counsel (NERC) whitepaper describing such an event and how to prevent it: http://www.nerc.com/docs/standards/sar/Frequency_Response_White_Paper.pdf (NERC is the United States quasi-governmental agency responsible for electric reliability rules.)
Other power plants under AGC are supposed to put the breaks on an uncontrolled voltage drop. Sounds like the system wasn't able to recover in this case -- either because there weren't enough other plants online to absorb the frequency deviation, or the backup plants that should have been ready to respond weren't quite so ready after all. Here's a link to the National Electric Reliability Counsel (NERC) whitepaper describing such an event and how to prevent it: http://www.nerc.com/docs/standards/sar/Frequency_Response_White_Paper.pdf (NERC is the United States quasi-governmental agency responsible for electric reliability rules.)