Operational Reliability (OR) is measured by assessing various aspects of outages and operation.
The formulas shown below are used to assess operational reliability.
| OR Measure |
Formula |
| Period of Demand (POD, hours): Measures the time the unit was planned to operate. |
POD = PH-RSH-SOH |
| Availability Factor (AF, %): Measures, on a percent basis, the unit's "could run" capability. Impacted by planned and unplanned maintenance. |
AF = 100*(PH-SOH-FOH)/PH |
| Running Availability (RR, %): Measures, on a percent basis, probability of avoidance of forced outages. Accounts for planned, unplanned, and administrative outages. |
RR = 100*(PH-FOH-SOH-AOH)/(PH-SOH-AOH) |
| Forced Outage Rate (FOR, %): Measures portion of time due to unplanned factors. |
FOR = 100*(FOH)/(SH+FOH) |
| Scheduled Outage Factor (SOF, %): Measures percent of time set aside for planned maintenance. |
SOF = 100*SOH/PH |
| Service Factor (SF, %): Percent of total period hours the unit is online. Varies due to site related or economic factors. |
SF = 100*ESH/PH |
| Mean Time Between Forced Outages (MTBFO, hours): Measure the nominal time between unscheduled forced outages. |
MTBFO = SH/(# Forced Outages) |
| Mean Down Time (MDT, hours): Measures the nominal duration the unit is down during the maintenance events. |
MDT = (SOH+FOH)/(# Forced Outages + # Planned Outages) |
Formula terms are defined as follows:
PH: Period Hours
RSH: Reserve Shutdown Hours
SOH: Scheduled Outage Hours
FOH: Forced Outage Hours
AOH: Administrative Outage Hours
SH: Service Hours
ESH: Equivalent Service Hours (service hours adjusted for derating)
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