**4. Discussion**

The article presents a method for testing and evaluating the reliability properties of wind farm devices in the operation process. Two new quantities were additionally proposed for the reliability tests of the object tested: the facility operation process quality function (Fc(t)) and the operation process absorption (non-readiness) function (Fch(t)). These two quantities, which feature the reliability of the working process of wind farm equipment, are original values that have not ye<sup>t</sup> been published in the literature.

The study, analysis and monitoring of the real operational process to identify the input data for the testing formed the foundation for the organization of the wind farm device simulation tests. The literature on the subject of dependability testing of complicated technical devices is constantly evolving. Three models of the wind farm operating process are presented in this study for simulation investigations. The first model performed was model A, which describes the operation process of wind farm installations equipped with intelligent systems that support decision-making regarding the safety of their use. The next model developed was model B, which describes the operation process of wind farm equipment

without any intelligent WPPES safety decision support systems. Another model was model C, which describes a simple (theoretical) operational process of wind farm equipment. To organize simulation tests, this article covers and describes the following issues:


The problem of testing the reliability properties of the wind farm equipment during its operation presented in the article is a difficult task. The difficulty of this is due to the acquisition of input data for the research. Numerical data describing the operation of the wind farm equipment can be obtained over a long period of time. The observation time (a measurement of the downtime and service life) in the actual operation process of the wind farm equipment is practically expressed in years during its "life". The only rational (sensible) attitude towards this type of study is a simulation test. This type of research requires the knowledge and a description of the actual operation process of the wind farm equipment and the determination of reliable input data for the research. At the core of each research, there is a good testing plan (how and in what manner to test) of the wind farm equipment. The grounds for the simulation study of the operation process of wind farm devices are formed by the models developed of the operation process organization.

The following reliability values were examined in the simulation tests to establish the credibility of the wind farm device in the operational process:


What forms the basis for the reliability of any simulation study results is the study plan developed, the input data and the quality of the models developed of a given process. The first problem is fundamental. Reliable input data can be determined only based on the study of appropriate time quantities occurring in the real study of the operation process of wind farm equipment. In the simulation study, the time data from the study of the technical documentation analysis of the operation process of the equipment of one wind farm located in the north of Poland was adopted. Models of the operation process of wind farm equipment are theoretical models presented in the literature-based Kolmogorov– Chapman equations. The models are developed properly and correctly. A good software tool: MaTlabon, was used in the simulation studies. On this basis, it can be assumed that the results obtained of the simulation studies are correct and reliable.
