## 1 Introduction  
Wind energy is the most well-known form of renewable energy. Studies on wind resource assessment, wind farm design, and wake effect analysis [1; 2; 3; 4; 5; 6] have been conducted to increase the energy efficiency of wind farms. To obtain reliable results from these studies, accurate wind measurement is very important, for which the installation of a met mast is essential. However, installing a met mast is expensive and time consuming. In particular, it is known to be very difficult to install an offshore met mast in the ocean for measuring offshore wind conditions. IEC 61400-12-1 1 st edition [7] for wind turbine power performance testing requires installing a met mast with a hub height within a distance of 2 to 4 times the rotor diameter from a test wind turbine. Although power performance testing should be carried out for all wind turbines at a wind farm, it hasbeen generally performed for a representative wind turbine due to the difficulty in installing met masts for all turbines. IEC 61400-12-2 [8] describes the methodology to estimate power curves of multiple wind turbines using the nacelle transfer function (NTF), which is the correlation between wind speeds measured using a cup anemometer on a met mast and a nacelle anemometer on a wind turbine. Using the NTF derived from a representative wind turbine, the power performance of other wind turbines can be evaluated if some requirements are satisfied. [PERSON] et al. [9] conducted power performance testing for two 3-MW wind turbines in compliance with the IEC 61400-12-2 procedure. [PERSON] et al. [10; 11; 12] proposed a method for identifying wind turbine degradation using NTF and analysed the annual capacity factor reduction rate for multiple wind turbines. Light detection and ranging (LIDAR) systems have received attention from the wind energy industry because of the advantages, including easy installation and a wide measurement range. Based on many research results on the reliability verification of ground LIDAR wind data [13; 14; 15; 16; 17; 18; 19; 20; 21], the IEC 61400-12-1 2 nd edition was published in 2015 [22]. It describes the procedure and requirements for a wind turbine power performance test using the rotor equivalent wind speed (REWS), which considers the wind shear covering the wind turbine rotor swept area. For this, the wind data above a hub height should be measured, for which the ground LIDAR has been mostly used. Recently, many investigations have been conducted to apply the nacelle LIDAR to wind turbine power performance testing. [PERSON] et al. [23; 24; 25; 26; 27] proposed a procedure for drawing a wind turbine power curve using nacelle LIDAR measurements and evaluated the uncertainty of the power curve. [PERSON] et al. [28; 29] clarified the reliability of the nacelle LIDAR measurements through comparison with the reference cup anemometer wind data. They also compared the power curves from the nacelle LIDAR, the cup anemometer and REWS measurements, which led to the conclusion that the nacelle LIDAR power curve was quite similar to the other power curves, with a relative error of less than 3.01% [30]. According to the demand for using nacelle LIDAR for power performance testing, the project team IEC 61400-50-3 was organized and has been working to publish the official international standard by the end of 2020 so that nacelle LIDAR can be used for wind turbine power performance testing without a met mast [31]. If it is possible to apply NTF derived from nacelle LIDAR measurements without a met mast to power performance testing, power curves of other wind turbines can be drawn, which will be done at a comparatively low cost and in a short period of time. In particular, it will be helpful for offshore wind turbine testing. The purpose of this study is to identify the applicability of NTF from nacelle LIDAR measurements (NTF\({}_{\text{NL}}\)) to wind turbine power performance measurements without a met mast and to further estimate the uncertainties of the power curves and the annual energy productions (AEP).