Summary of Outage & Maintenance Methods
Aurora offers the following options to model forced outages and maintenance schedules. Click on the links for more information.
FORCED OUTAGE RATE: The Forced Outage column in the Resources, Fuel, or New Resources tables allows the user to specify the percentage of time the resource will be unavailable due to unscheduled outages. The Forced Outage field reduces the plant capacity by multiplying the plant capacity by the quantity 1 minus the forced outage rate divided by 100. The use of this column is controlled by the Outage method settings.
Hourly Derate Method: The Hourly derate method option is a deterministic method in which the capability for each resource will be derated hourly based upon its current forced outage rate. No random outage method will be applied. The unit capacity is de-rated by the forced outage rate for each dispatch hour. Example: For a plant with a capacity of 120 MW and a Forced Outage rate of 10%: 120 MW *(1-10/100) = 108 MW of generating capability would be applied to the unit in every hour.
Frequency Duration Method: The Frequency duration outage method option is a stochastic method that simulates random unscheduled outages. This method allows units to fail or return to service at any time within the simulation, not just at the beginning of a month or a day. The frequency and duration method assumes units are either fully available or completely out of service. Partial capacity outages are not modeled in this implementation.
Convergent Method: The Convergent outage method provides another flexible way to model random resource outages. In contrast with the frequency duration outage method, this method ensures convergence to an entered forced outage rate in every risk iteration. The logic considers each unit’s forced outage rate, mean repair time, and planned maintenance schedule, while at the same time seeking to adhere to expected overlapping outages for groups of resources. The setup also affords a straightforward way to change some input data while still keeping the outage pattern for resources the same.
MAINTENANCE RATE: The Maintenance Rate column in the Resources, Fuel, or New Resources tables allows the user to specify the percentage of time the resource will be unavailable due to scheduled outages. The maintenance rate specified reduces the plant capability for each dispatch hour.
The maintenance rate is determined by multiplying plant capacity by the quantity 1 minus Maintenance Rate divided by 100. The unit capacity will be de-rated by the Maintenance rate for each dispatch hour. Example: For a plant with a capacity of 120 MW with Maintenance Rate of 10%: 120 MW * (1-10/100)= 108 MW of generating capability would be applied to the unit in every hour.
AUTOMATED MAINTENANCE SCHEDULING STUDY (MST): Aurora will schedule maintenance to maximize the daily reserve margin over a plant’s maintenance cycle for the zone or pool in which that plant resides. Aurora determines the order in which units will be scheduled based on their required GW-Days (gigawatts of capacity multiplied by number of days) of outage, from highest to lowest. Units having the same GW-Days of outage will be scheduled arbitrarily relative to each other. During a typical maintenance run, Aurora will schedule the maintenance outage from January of the start year through December of the end year plus one month to allow for end of year scheduling. The results of this capability is the creation of a new Maintenance Schedule table (MST) which at the end of the study is placed in the input database and selected for use in the study. Click here for more information.
Summary of Outage & Maintenance Methods
