Vref Settings - Underwriters-Labs/renewables.openwind.help GitHub Wiki

This dialog is used to allow the user to determine which method or methods are used to determine the overall Vref as well as what is reported.

Vref settings dialog.

Enable UL Legacy MIS Gumbel method - this is the legacy UL method which is based on identifying storms as being periods with winds in the top 95th percentile. A cumulative distribution curve is fitted using the Gumbel method.

Enable EWTS II 'Exact' - uses a variant of the EWTS II method

Enable EWTS II Gumbel - uses a variant of the EWTS II method

Enable EWTS II Davenport - uses a variant of the EWTS II method

Simple MIS Gumbel method - uses a variant of the method of independent storms combined with a simple Gumbel fitting algoritm.

Harris 1996 MIS Gumbel method - uses a variant of the method of independent storms combined with the Harris 1996 Gumbel fitting algoritm.

Harris 1999 MIS Gumbel method - uses a variant of the method of independent storms combined with a Harris 1999 Gumbel fitting algoritm.

Overall Vref value is - allows the user to choose whether to make Vref the maximum of the currently selected options or the average or to choose one particular method whilst still reporting the values arrived at by the other methods.

For each of the Simple, Harris 1996 and Harris 1999 options, the user can also specify the following parameters:

Threshold for storm wind speeds - this is the value above which a storm is considered to be under way. If the "Auto" option is activated then Openwind will vary the threshold until there are precisely 20 storms per year.

Minimum hours between storms - this is the amount of time that needs to pass without wind speeds above the threshold value, for the first storm to be considered to have passed and for a new storm to have started. This is the "independent" part of "independent storms".

Precondition maxima using exponent - this is covered under Preconditioning and is a way to get a better linear fit through the resulting points.