| A true black start has several factors (which make it difficult and notable): 1. The grid has to fully collapse with no possibility of being rescued by interconnection 2. As a result, a generation asset has to be started without external power or a grid frequency to synch to 3. An asset capable of this is usually a small one connected to a lower voltage network that has to then backfeed the higher voltage one 4. Due to the difficulty of balancing supply/demand during the process, the frequency can fluctuate violently with a high risk of tripping the system offline again None of this applies in yesterday's case: The rest of the European synchronous grid is working just fine. News reports stated Spain restored power by reconnecting to France and Morocco. By reestablishing the HV network first, they can directly restart the largest generation asset with normal procedures. As they bring more and more load or generation online, there's little risk of big frequency fluctuations because the wider grid can absorb that. |