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Glossary - O

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

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Term/Acronym Definition
O&M Operations and Maintenance
OCN Operating Condition Notice

Off-Line

The status of a Resource that is not synchronously interconnected to the ERCOT System.

Oklaunion Exemption The export schedules from the Public Service Company of Oklahoma, the Oklahoma Municipal Power Authority, and the AEP Texas North Company for their share of the Oklaunion Resource over the North DC Tie that are not treated as Load connected at transmission voltage, are not subject to any of the fees described in Section 4.4.4, DC Tie Schedules, and are limited to the actual net output of the Oklaunion Resource.
On-Line The status of a Resource that is synchronously interconnected to the ERCOT System.
On-Peak Hours Hours ending in 0700 to 2200 CPT from Monday through Friday excluding NERC holidays.
Operating Condition Notice (OCN) The first of four levels of communication issued by ERCOT in anticipation of a possible Emergency Condition.
Operating Day The day, including hours ending 0100 to 2400, during which energy flows.
Operating Hour A full clock hour during which energy flows.

Operating Period

A two-hour period comprised of the Operating Hour and the clock hour preceding the Operating Hour.

Operating Reserve Demand Curve (ORDC) A curve that represents the value of reserves at different reserve levels based on the probability of reserves falling below the minimum contingency level and the Value of Lost Load (VOLL), as further described in the Methodology for Implementing Operating Reserve Demand Curve (ORDC) to Calculate Real-Time Reserve Price Adder.
Opportunity Outage See Outage
Other Binding Documents List List of Other Binding Documents as managed in paragraph (3) of Section 1.1, Summary of the ERCOT Protocols Document.
Outage The condition of a Transmission Facility or a portion of a Facility, or Generation Resource that is part of the ERCOT Transmission Grid and defined in the Network Operations Model that has been removed from its normal service, excluding the operations of Transmission Facilities associated with the start-up and shutdown of Generation Resources.

Forced Outage
An Outage initiated by protective relay, or manually in response to an observation by personnel that the condition of equipment could lead to an event, or potential event, that poses a threat to people, equipment, or public safety.

For a Generation Resource, an Outage that requires immediate removal, either through controlled or uncontrolled actions, of all or a portion of the capacity of the Resource from service through automated or manual means. This type of Outage usually results from immediate mechanical/electrical/hydraulic control system trips and operator-initiated actions in response to a Resource’s condition.

Maintenance Outage
An Outage initiated manually to remove equipment from service to perform work on components that could be postponed briefly but that is required to prevent a potential Forced Outage and that cannot be postponed until the next Planned Outage. Maintenance Outages are classified as follows:
  1. Level 1 Maintenance Outage -- Equipment that must be removed from service within 24 hours to prevent a potential Forced Outage;
  2. Level II Maintenance Outage -- Equipment that must be removed from service within seven days to prevent a potential Forced Outage; and
  3. Level III Maintenance Outage -- Equipment that must be removed from service within 30 days to prevent a potential Forced Outage.
Opportunity Outage
An Outage that may be accepted by ERCOT when a specific Resource is Off-Line due to an Outage.

Planned Outage
An Outage that is planned and scheduled in advance with ERCOT, other than a Maintenance Outage or Opportunity Outage.

Simple Transmission Outage
A Planned Outage or Maintenance Outage of any Transmission Element in the Network Operations Model such that when the Transmission Element is removed from its normal service, absent a Forced Outage of other Transmission Elements, the Outage does not cause a topology change in the LMP calculation and thus cannot cause any LMPs to change with or without the Transmission Element that is suffering the Outage.
Outage Scheduler The application that TSPs or QSEs use to submit Notification of Outages or requests for Outages to ERCOT for approval, acceptance, or rejection.
Output Schedule The self-scheduled output for every five-minute interval of a Resource provided by a QSE before the execution of SCED.