This thesis was ordered by Suomen Hyötytuuli Oy. The aim of the thesis was to identify possible faults in substation and create operational instructions to substation fault situations. At first the critical components of substation were researched, and their theory explained. The structure of the electrical grid at the chosen windfarm was also explained. The information was gathered from books and interviews and later in the work the knowledge which was developed through the work was also utilized.

A fault mapping was created for possible faults in the case substation and electrical grid with the help of personnel at Hyötytuuli. To understand the structure of the electrical grid, an employee created a simulator during this thesis which is also included in this thesis.

The main result of this thesis is the operational instructions for the case substation. The instructions support the work of Hyötuuli’s control room operators and service personnel by clarifying which actions to take. The other result of this thesis is to support the operation instructions and provide deeper understanding of the case electrical grid and substation.