# Technological Advances on Fault Diagnosis in Wind Turbines: A Patent Analysis
## 1 Introduction
The thermography technique uses an infrared (IR) camera acting as a sensor, and the system makes it possible to detect surface damage on the different elements of wind turbines [29]. Structural defects cause friction between the constituent elements of wind rotors, which, in turn, generates heat. Heat flows along materials can be accurately assessed by capturing and analyzing thermal images. The benefits of using the thermography technique are visual damage description and full-field measurements. In addition, this method could be applied for massive inspections due to the short time consumption. [PERSON] et al. [30] utilized a thermography system based on a continuous line laser and an algorithm to measure internal delaminability in rotating blades. The thermal images demonstrated the explicit defect by color difference. [PERSON] et al. [31] evaluated passive and active infrared thermographic techniques employed on wind turbine blades to detect multiple defects, such as delamination, air bubbles, and structural defects within glass-fiber-reinforced polymer composite blades. Comparing the methods mentioned above, the vibration analysis technique, considered traditional, usually indicates failures linked to mechanical and electrical parts, and although it is widely used, it has limitations, such as difficulty in identifying the nature of the failure, many sensors are required to detect the location and severity of the damage, and environmental conditions can make damage detection difficult and inaccurate. In addition, it makes it difficult to differentiate between the vibrations caused by the environment or the operating conditions and the vibrations caused by blade damage [16]. On the other hand, the thermography technique, which can be used in various environmental conditions, presents some disadvantages, including the requirement for expensive thermal imaging cameras; the technique is also sensitive to temperature changes and is affected by air temperature and humidity [16; 32; 33]. Both techniques have advantages and limitations, meaning that scientific, technical development is essential for improving traditional techniques and developing new ones. In recent years, research advances have offered numerous new solutions for various fault problems. Many researchers have focused on wind speed variability, improving power generation efficiency, and decreasing the cost of energy generation. A greater understanding of the evolved models and techniques could positively impact the future of wind energy research. Patents play an important role in the development and innovation process, directly supporting three important areas, such as: providing back-up support for R&D; by providing state-of-the-art analysis in a given technological area; supporting the acquisition and protection of IP. In addition, the study of patents gives direct support to companies and the development of business and strategic transactions. Important data for analyzing competitors, understanding a particular technological area, determining patent applicability, and identifying potential alliance partners are made available [34]. In view of that, this study had the objective of performing a technological prospection focused on patents in order to verify the technological panorama of the different techniques used to identify faults and defects in wind turbines.