Wind farm protection using an IEC 61850 process bus architecture

Wind generation and wind farms are becoming an important part of the generating capacity of the modern utility grid. Protection of wind turbines, and wind farm collector systems, has been the subject of numerous technical papers over recent years, as wind generation grows more prevalent. These papers have focused on the basics of protecting the wind turbines, protecting the wind farm, and modelling of wind farms for stability studies. However, few have focused on practical aspects of protection and control systems when wind turbines and collectors systems are distributed over many square kilometres of surface area. There are design, construction, and maintenance decisions to make for a wind farm, such as where to physically mount protective relays, laying out copper wiring between measurement sources and protective relays, and realistic and affordable maintenance programs for protective relays. Maintenance can quickly become an issue if relays are located at each individual wind turbine. These decisions become much more complicated when the wind farms are located offshore, as the cost of installation, and the cost of maintenance, increase dramatically. This paper proposes a protection and control (P&C) approach based on IEC61850 process bus architecture. Ruggedized Merging Units (MUs) can be installed at individual wind turbines to acquire AC measurements (as raw sampled values) and status information, as well as provide control points. Data is transmitted via IEC 61850 messages over a fibre optic communications network to a Central Relaying Unit (CRU) which executes P&C functions for a whole wind farm.