Leading Indicator: IROL Violations
Six violations of Standard TOP-007-0 were found in 2007. All six were violations of procedural requirements. No IROLs (Interconnection Reliability Operating Limit) were exceeded longer than 30 minutes in 2007. NERC is working with Reliability Coordinators to collect data on IROL near misses, where IROLs were exceeded for duration of 30 minutes or less.
SOL (System Operating Limit) is the value (such as MW, MVar, Amperes, Frequency or Volts) that satisfies the most limiting of the prescribed operating criteria for a specified system configuration to ensure operation within acceptable reliability criteria. An IROL is a SOL that, if violated, could lead to instability, uncontrolled separation, or cascading outages that adversely impact the reliability of the bulk power system.
Following a contingency or other system event that results in an SOL or IROL violation (or causing the system to operate outside set reliability boundaries), Transmission Operators are obligated to return its transmission system to within SOL or IROL as soon as possible. The SOL & IROL violation trend indicates whether the system is controlled within acceptable limits during normal conditions and after contingencies. Please refer to NERC reliability standard TOP-007-0 - Reporting SOL and IROL Violations for more details.
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