# Technological Advances on Fault Diagnosis in Wind Turbines: A Patent Analysis
## 3 Results and Discussion
The comprehensive stage defined the development targets of the wind power industry and established a stable cost-sharing system by publishing the Renewable Energy Law of the People's Republic of China in 2006 [83]. In the stable development stage (since 2010), China has become one of the largest technology-developing countries in the world, and, in light of this, companies have explored the development of raw materials, component manufacturing, wind turbine manufacturing, and wind-farm management in order to decrease costs and increase the competitiveness of the wind energy market in the world. Figure 3: Geographical distribution of the analysis of the main countries/regions of the depositors of the prospected technologies with their number of patent documents. EP—European Patent Office; WO—World Intellectual Property Organization. By the end of 2010, four Chinese companies were among the world's top 10 wind turbine manufacturers [78]. It is important to mention that one of the reasons for the great technological advance achieved by China is the growing collaboration between research centers and private companies. An example of this collaboration was the creation of the Offshore Wind Power Research Institute by the Shanghai Electric Wind Power Group and Zhejiang University and also the Shanghai Donghai Wind Power Co., Ltd., who cooperated with the Shanghai Electric Power University to develop floating wind power [78]. This collaboration can also be seen in the results found in the patents. The patent refers to an infrared thermal image detection method for detecting micro-defects in the blades of large wind turbines, and the Shenyang University of Technology (Tiexi, Shenyang, China) is the applicant: deposited by Nanjing Ruigong Engineering Testing Co. Ltd. (Nanjing, China), the patent is related to a nondestructive testing device for wind turbine blades. Considering all these important efforts, and under the guidance of wind power policies, China has grown significantly in the wind energy industry and market. However, there are still some problems in the industry, such as the difficulty of accommodation, inadequate financial subsidies, and imperfect market systems, which can occur due to imperfect policies, inadequate implementation of such policies, etc. [84]. Therefore, China still needs to improve policies and continue to develop wind power technology in order to solve the problems that might arise along the way. The United States (U.S.) was the second country found in terms of research conducted and started seriously harnessing wind power after the oil crisis. In 2021, wind energy accounted for 32% of the country's total energy capacity, with 13.4 GW of wind capacity taking the cumulative total to almost 136 GW by the end of the year [85,86]. The country's investments in wind energy were about USD 20 billion, with the aim of implementing new wind power projects by 2021, accumulating to about USD 270 billion since the early 1980s [87]. One of the ways that the U.S. used to support the development of wind power was the establishment of the National Offshore Wind Power Strategy: creating the U.S. Offshore Wind Power Industry released by the United States Department of Energy and the Department of the Interior. This strategy planned to invest in research and innovation, wind turbine manufacturing, and grid technology [88]. In terms of policies, the government provides support from federal funds and wind energy technology foundations, such as credit loans and financing R&D designs and equipment manufacturing, as well as wind farm construction. These policies prioritized the development and promotion of wind energy technology and invested substantial R&D technical subsidies in wind energy technology [89]. It is worth mentioning that two international organizations were identified, these being the World Intellectual Property Organization (WIPO) and the European Patent Office (EPO), with 60 and 49 applications, respectively.