Response Analysis
IEC TS 62600-2 culminates in a response analysis for the simulations or tank testing done for the WEC.
The developer uses the downloaded surface elevation time series, performs tests while collecting response variables (motions of or forces exerted on the WEC device), then performs an extreme value analysis on each of the response variables captured.
See the web interface documentation for information on creating the uploaded response file to the DLC Generator.
IEC TS 62600-2 Section 7.3 has detailed requirements for the testing.
Extreme Value Analysis
MHKiT is used to calculate the extreme value with mhkit.loads.extreme.short_term_extreme.
The extreme value analysis is performed to align with the IEC TS 62600-2 Section 7.3 specifications, using a 3-hour sea state as the short-term period.
See comparison of methods for estimating short-term extreme response of wave energy converters for more information.
Statistical Method
The method selected uses the same univariate distributions as described in Statistics.
Peaks Over Threshold
Currently, the Peaks Over Threshold implementation for the short_term_extreme function uses 1.4 standard deviations above the mean as the Threshold value. Sometimes this implementation leaves too few values to be able to approximate the extreme characteristic.
Come back for a future release where the threshold is automatically optimized using methods defined here.
Partial Safety Factors
IEC TS 62600-2 specifies safety factors to be applied to achieve a target safety level of SL2. The DLC generator automatically reports the extreme characteristic with the ULS (Ultimate Limit State, see IEC TS 62600-2 Section 7.3.4.2) applied. The environmental load category ULS values are used in the tool.
The tool doesn’t have any knowledge of what DLC the given response is associated with. Use IEC TS 62600-2 Table 7 for more details on what safety factors apply to the DLC that was being assessed.
See IEC TS 62600-2 Section 7.3.5 Table 6 for details and caveats on the partial safety factors.