In the world of electricity, physical capacity may be unavailable. It could be the result of scheduled maintenance or it may concern unplanned unavailability; the latter, typically, being an ad hoc event. Irrespective of the type of maintenance, it may concern information which impacts the market. In order to create a level playing field for market participants, under certain regulations (e.g. the REMIT regulation), an obligation applies to make the information publically available. Publication is mandatory when regulation classifies the information as inside information.
Electricity generation capacity may face a sudden unavailability, for instance, due to a technical failure, so that an outage appears. In such a case, unplanned unavailability appears. Owners of electricity generation capacity also schedule for required maintenance, typically once a year. In such as case, planned unavailability appears. Both planned and unplanned unavailability could impact the market. Therefore, irrespective of the way the unavailability appears, it may have to be published.