DNV

Ships occasionally experience blackouts, with a temporary loss of propulsion. Fortunately, most incidents do not have any significant consequences, as they usually occur at open sea.

Nevertheless, blackouts should be avoided. Planning, training, and contingency measures are all essential elements to effectively manage the risk of blackouts, and the combined effect of measures will have the greatest impact on safety.

https://www.dnv.com/news/11-statutory-blackouts-causes-prevention-effective-recovery/