Investigations of different Function Allocations in SA Systems enabled by IEC 61850

At least since 2006 the standard IEC 61850 for communication in substations is in commercial use providing interoperability in substation automation systems between devices from different suppliers. Its approach is based on the split between applications and communication, functions and implementation and, therefore, supports also the free allocation of functions to IEDs. This allows the question for an optimal allocation regarding the functional requirements of SA, its impact on the communication system, performance of functions, engineering effort and reliability, and on the cost level. Common SA systems are some mix between a total centralized and decentralized allocation providing the well- known functions on station, bay and process level. The two extreme solutions are positioned and it is evaluated if the common mix is an optimal one. The result is a proposal for the best allocation of existing functions to IEDs. Depending on given functional requirements and not too strict boundary conditions, improvements are possible exploiting the full capabilities of IEC 61850, if accepted.