IEC 61400-12-5:2022

IEC 61400-12-5 ®
Edition 1.0 2022-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 12-5: Power performance – Assessment of obstacles and terrain

Systèmes de génération d'énergie éolienne –
Partie 12-5: Performance de puissance – Évaluation des obstacles et du terrain

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IEC 61400-12-5 ®
Edition 1.0 2022-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –

Part 12-5: Power performance – Assessment of obstacles and terrain

Systèmes de génération d'énergie éolienne –

Partie 12-5: Performance de puissance – Évaluation des obstacles et du terrain

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-5603-9

– 2 – IEC 61400-12-5:2022 © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols, units and abbreviated terms . 9
5 General . 9
6 Measurement sector procedure to be used for power performance measurements
according to IEC 61400-12-1 . 10
6.1 General . 10
6.2 Requirements regarding neighbouring and operating wind turbines . 11
6.3 Requirements regarding obstacles . 11
6.4 Method for calculation of sectors to exclude . 12
6.5 Special requirements for extended obstacles . 15
7 Measurement sector procedure to be used during the determination of the nacelle
transfer function (NTF) between free wind speed and nacelle anemometer wind
speed . 15
8 Measurement sector procedure to be used during the determination of the nacelle
power curve (NPC) . 15
8.1 General . 15
8.2 Requirements regarding neighbouring and operating wind turbines . 16
8.3 Requirements regarding obstacles . 16
8.4 Calculation of the excluded sector . 17
8.5 Self-consistency check procedure for the measurement sector . 18
9 Assessment of terrain at the test site . 19
10 Terrain classification for evaluation of NTF and NPC . 22
10.1 General . 22
10.2 RIX indices . 22
10.3 Average slope . 22
10.4 Determine terrain class . 23
10.5 Ridge formations . 24

Figure 1 – Sectors to exclude due to wakes of neighbouring and operating wind
turbines and significant obstacles . 13
Figure 2 – An example of sectors to exclude due to wakes of the wind turbine under
test, a neighbouring and operating wind turbine and a significant obstacle . 14
Figure 3 – Example of the result of a sector self-consistency check . 19
Figure 4 – Illustration of area to be assessed, top view . 20
Figure 5 – Example of determination of slope and terrain variation from the best-fit
plane: "2L to 4L" and the case "measurement sector" (Table 5, line 2) . 21
Figure 6 – Determination of slope for the distance "2L to 4L" and "8L to 16L" and the
case "outside measurement sector" (Table 5, line 3 and line 5). 21

Table 1 – Interfaces from other International Standards to this document . 10
Table 2 – Interfaces from this document to other International Standards . 10
Table 3 – Obstacle requirements: relevance of obstacles . 12

Table 4 – Obstacle requirements: relevance of obstacles . 17
Table 5 – Test site requirements: topographical variations . 20
Table 6 – Slope terrain classification . 23
Table 7 – RIX terrain classification . 23
Table 8 – Final terrain class . 23
Table 9 – Maximum ridge step effects on terrain class . 24

– 4 – IEC 61400-12-5:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –

Part 12-5: Power performance –
Assessment of obstacles and terrain

FOREWORD
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