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Appendix B — Event Categories and Levels of Analysis The purpose of this document is to identify events that may require further analysis. Each event is categorized to help the Regional Entities (REs) and registered entity(s) impacted determine the appropriate level of analysis or review. Event Analysis Levels Impacted registered entity(ies), the associated RE and when appropriate, NERC, will collaboratively determine the appropriate level of any event analysis that should be conducted. The following provides a summary of the various reports that are expected per the EAWG process: Event Report — prepared by impacted entities, sent to NERC and the affected RE. The event report is a generic term and the actual notification may come from a variety of sources such as, but not limited to EOP-004, OE-417, and/or ES-ISAC report. Event Analysis Report — A report detailing what happened and why. Prepared by either the impacted entity or the impacted entity in coordination with the event analysis team as defined in the EA process. The following will be used to determine the level of analysis to be conducted: Category 1 — event report. (Normally there is no follow-up anticipated for category 1 reports unless requested by the RE). Category 2 and 3 — An event report and an event analysis report prepared by the registered entity and follow-up as directed by the RE. Category 4 and 5 — An event report and an event analysis report developed by an event analysis team led by the RE or NERC. Operating Reliability Event Categories Operating reliability events are those events that are deemed to have significantly impacted the reliable operation of interconnected system. These events are divided into five (5) categories that account for their different system impact and help determine the level of analysis that is warranted1. The lists below are intended to provide examples as to the types of events that fall into each category. For events not covered below, the impacted entity, in conjunction with the RE, will determine the categorization. Category 1: An event resulting in one or more of the following: a. The loss of a bulk power transmission component(s) in response to a single-phase line-toground fault with delayed clearing2 (stuck breaker or protection system failure). (Refer to Table I. Transmission System Standards — Normal and Emergency Conditions of the TPL standards categories C6 through C9). 1 The highest category that characterizes an event shall be used. 2Delayed clearing of a fault is due to failure of a circuit breaker or of any protection system component such as a relay or current transformer, and not because of an intentional design delay. b. Loss of three or more bulk power system (BPS) elements (i.e. generators, transmission lines, and buses). c. Frequency below the Low Frequency Trigger Limit (FTL) or above the High FTL for more than 15 minutes.3 . d. Intended and controlled system separation by the proper operation of a Special Protection System Scheme (SPS) / Remedial Action Scheme (RAS) in Alberta from the Western Interconnection, New Brunswick or Florida from the Eastern Interconnection. e. Failure, degradation or misoperation of SPS/RAS. f. Unintended loss of an entire dc converter station g. System wide voltage reduction of 3 percent or more h. Public appeal to reduce the use of electricity for purposes of maintaining the continuity of the BPS i. Fuel supply emergencies that could impact BPS adequacy or reliability j. Unintended system separation resulting in an island of up to 1,000 MW. Category 2: An event resulting in one or more of the following: a. Loss of all BPS control center voice or data functionality for 30 minutes or more. b. Unplanned evacuation from BPS control center facility c. Voltage excursions equal to or greater than ±10 percent lasting more than five (5) minutes d. The loss of an entire generation station of five (5) or more generators (aggregate generation of 500 MW or higher). e. Loss of off-site power (LOOP) to a nuclear generating station. f. Load shedding resulting in a loss of load of 100 MW or greater as a result of: 1. Manual load shedding; 2. Underfrequency load shedding; or 3. Undervoltage load shedding. g. Unintended system separation resulting in an island of 1,001 MW to 4,999 MW. h. Equipment failures or SPS/RAS actions which result in the loss of firm system demands for more than 15 minutes, as described below: 1. Entities with a previous year recorded peak demand of more than 3,000 MW are required to report all such losses of firm demands totaling more than 300 MW. 2. All other entities are required to report all such losses of firm demands totaling more than 200 MW or 50 percent of the total customers being supplied immediately prior to the incident, whichever is less. i. An Interconnection Reliability Operating Limit (IROL) violation as defined in reliability standard TOP-007. 3 In case of an FTL exceedence, the reporting of the event occurs automatically through the NERC ACE and Frequency Monitoring System. Analysis of these events will normally be conducted by the NERC Operating Committee’s Resources Subcommittee. Category 3: An event resulting in one or more of the following: a. The loss of load or generation (excluding SPS/RAS, UFLS, or UVLS actuation) of 2,000 MW or more in the Eastern Interconnection or Western Interconnection, or 1,000 MW or more in the ERCOT or Québec Interconnections. b. Unintended system separation resulting in an island of 5,000 MW to 10,000 MW. c. Unintended system separation resulting in an island of Alberta from the Western Interconnection, New Brunswick, or Florida from the Eastern Interconnection. Category 4: An event resulting in one or more of the following: a. The loss of load or generation from 5,001 MW to 9,999 MW (excluding SPS/RAS as noted in Category 2, UFLS, or UVLS actuation). b. Unintended system separation resulting in an island of more than 10,000 MW (with the exception of Alberta, New Brunswick, and Florida as described in category 3C above). Category 5: An event resulting in one or more of the following: a. The loss of load of 10,000 MW or more. b. The loss of generation of 10, 000 MW or more.