During part of the electric power emergency in the ERCOT region of Texas last week, the ERCOT system imported power from Mexico to reduce the extent of the blackouts needed to keep the ERCOT grid operating.
The interconnections between ERCOT/Texas and Mexico are relatively recent. The summary of the March 2009 meeting of the ERCOT board reported the following information:
MEXICO GRID CONNECTIONS BEGIN COMMERCIAL OPERATIONS
The direct current (DC) ties with the Comisión Federal de Electricidad (CFE) are open to commercial transactions, effective March 12. These ties include:
* Eagle Pass (DC-S), 30 MW
* Sharyland Railroad (DC-R), 150 MW
* Laredo Variable Frequency Transformer (DC-L), 100 MW.
The import and export limits of the connections with CFE are calculated daily and published at this link. [Link seems not to be working. -MG]
The ERCOT grid is not synchronously connected with any other grids. Connections to other grids are limited to direct current ties which allow the controlled transfer of power between the ERCOT system and another electrical system without the two systems being synchronized.
The ERCOT grid also has DC ties with the Southwest Power Pool region at Oklaunion (220 MW) and at Monticello (600 MW), both in the north Texas area.
The CFE ties have been used for mutual emergency assistance between ERCOT and CFE but were not previously available for commercial transactions. Mexico has assisted ERCOT through the ties and the Laredo connection during capacity-shortfall events, and ERCOT has also assisted CFE on emergency occasions.