Generator Forced Outage Rate

Units:	%
Mode:	Input/Output
Multi-band:	True
Default Value:	0
Validation Rule:	Between 0 And 100
Key Property:	No
Description:	Expected proportion of time the facility is unavailable due to forced outage

Input

Generator Forced Outage Rate sets the expected level of unplanned outages, which result in a partial or complete loss of generating capacity for a certain period of time. See the article Planned and Random Outages for details about the repair time distribution.

Table 1: Forced Outage Rate Example
Property	Value	Units
Forced Outage Rate	2.5	%
Min Time to Repair	3	hrs
Mean Time to Repair	36	hrs
Max Time to Repair	100	hrs

In the example in Table 1 the facility is expected to be out of service 2.5% of the time and each time it is out-of-service the repair will fall in the range 3-100 hours with the mode of that distribution being 36 hours.

The property Forced Outage Rate Denominator controls the interpretation of Forced Outage Rate, which has been developed with reference to the IEEE Standard definitions.

The setting can take the following values:

Time (value = 0, default): Forced Outage Rate = Forced Outage Hours / time
Operating Time (value = 1): Forced Outage Rate = Forced Outage Hours / (Operating Hours + Forced Outage Hours)

By default then, the Forced Outage Rate above of 2.5% implies that on average units will be out of service (OOS) 0.025 x 8760 = 219 hours per annum. The repair time distribution is constant (Mean Time to Repair only is given) thus there will be on average 219 / 36 = 6 random outage events per annum each of 36 hrs.

Note that Forced Outage Rate is a multi-band property, meaning you can define several types of outage with different outage duration functions. You can also model partial outages with the Outage Rating property.

It is important to note how Forced Outage Rate acts in combination with Units Out. Forced Outage Rate is converted to Mean Time Between Failures (MTBF) with the formula:

MTBF = (1 - Forced Outage Rate) × Mean Time to Repair / Forced Outage Rate

MTBF ignores any pre-defined outage period. For example if Forced Outage Rate = 10% and Units Out implies the unit is out-of-service for 25% of the year, in the results you will see an annual Forced Outage Rate of 7.5% i.e. the unit will be forced out 10% of the available hours.

You can change this behavior and have the forced outage rate automatically adjusted such that the annual rate is unaffected by Units Out with the setting Stochastic EFOR Maintenance Adjust.

Output: As output, Forced Outage Rate reports values consistent with the Forced Outage Rate Denominator setting i.e. by default, it is the percentage of time the unit is out-of-service in any given period.