# How to calculate RIX0.04 (Regarding IEC 61400-12-2)

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Hi, there.

If RIX0.04 is 9m, (in the effective wind vane) it is converted to the ratio of the distance where the delta Z is more than 9m out of 20 times the hub height.
How is delta Z calculated here?😄

Is it just sum of (exceed distans)/ 20times HH ?

And, about as this limit RIX0.04>16 : Is 16 the maximum value? or It means average 16% of the total range (or the effective vane) ?

Thanks and regards,

NY Kim

Edited by NYKim
• 2 weeks later...

Hi Kim,

The dZ values for the RIX number evaluation in IEC 61400-12-2 are calculated by terrain elevation at points distributed with 30m separation along the centerline of each 10 degree sector. The dZ values are defined by elevation differences of neighboring points, and the slopes are the elevation differences divided by the point separation (30m). This measure is not related to the distance from the turbine, so I am not sure the conversion you suggest will makes sense. The RIX number evaluation depends on a threshold, which is scaled by H+D (hub height plus rotor diameter) and we evaluate a RIX value by several thresholds.

There is an explanation in the WAT help file section IEC 61400 standards>IEC 61400-12-2>terrain assessment but it is very brief, so I recommend that you read section 6.3 of the IEC 61400-12-2 standard for a full explanation.

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