Glossary - o

For your convenience, this page contains an alphabetically organized list of terms, definitions and common acronyms used in the electric utility industry.

O

Term/Acronym	Definition
OOM	Out of Merit Order
OOMC	Out of Merit Capacity
OOME	Out of Merit Energy
Obligation	Total Obligations scheduled by a QSE that are comprised of energy Obligations and Ancillary Services Obligations where: Energy Obligations = Load + losses + energy sales + energy exports; and Ancillary Services Obligations = ERCOT allocated Ancillary Services Obligations (which may be self-arranged) + Ancillary Services sales (to ERCOT or to other QSEs)
On-line	Resources that are synchronously interconnected to the ERCOT System.
Operating Condition Notice	The first of four possible levels of communication issued by ERCOT in anticipation of a possible emergency condition detailed in Section 5.6, Emergency and Short Supply Operation.
Operating Day	The actual day, including hours ending 0100 to 2400, during which energy is flowing.
Operating Guides	Guidelines approved by the ERCOT Board describing the reliability standards for ERCOT.
Operating Hour	The current clock hour.
Operating Period	A two-hour period comprised of the Operating Hour and the hour preceding the Operating Hour.
Operating Plan	A plan developed by ERCOT to operate the ERCOT System in Real Time.
Operational Constraint	Anticipated or actual security violation or overload of a transmission element, based on actual network topology.
Operational Model	The transmission model based on actual network topology of the ERCOT System.
Out of Merit Capacity	Capacity provided by a Resource selected by ERCOT outside the bidding process to resolve a reliability or security event when no Market Solution exists.
Out of Merit Energy	Energy provided by a Resource selected by ERCOT outside the bidding process to resolve a reliability or security event when no Market Solution exists.
Out of Merit Order (OOM)	The selection of Resources for Ancillary Services that would otherwise not be selected to operate because of their place (or absence) in the bidding process for that service.
Outage	Removal of a Facility from service to perform maintenance, construction or repair on the Facility for a specified duration. Forced Outage A component failure or other condition that requires that the equipment be removed from service immediately or up to and including the next weekend. Maintenance Outage Removing Transmission Facility or Resource Facility equipment from service to perform work on specific Facility components that could be postponed past the very next weekend. Such work is required to prevent a potential Forced Outage and that could not be postponed until the next Planned Outage. Planned Outage Any major or minor Transmission Facility or Resource Facility equipment maintenance that is planned and scheduled in advance as submitted to ERCOT.