REQUIREMENTS OF INTEROPERABLE DISTRIBUTED FUNCTIONS AND ARCHITECTURES IN IEC 61850-BASED SA SYSTEMS

Interoperability according to the standard IEC 61850 means the capability of two or more intelligent electronic devices (IEDs) to exchange information and to use it in the performance of their functions for correct co-operation. Neither the actual definition, i.e. algorithms, nor the actual allocation of functions fall inside the scope of the standard. The utilities and vendors of SA systems have to take into account that even with the standardized data model and services as well as the comprehensive description by the substation configuration description language, the IEC 61850 standard allows certain degrees of freedom which especially surface in complex distributed functions. The application of distributed functions to complex switchyard topologies with dynamic power flows, i.e. changes of incoming and / or outgoing feeders, is very challenging, since IEC 61850 does not provide a clear model for this kind of applications and their functional demands. For these, it is not always possible to find an interoperable distributed solution that is valid for all vendor-specific implementations. It is therefore strongly recommended that the definition of data interfaces shall, in future editions of the standard, handle more complex topologies. These extended definitions shall cover e.g. protection zones for breaker failure protection, electrically connected parts for reverse blocking schemes as well as interlocking. Another gap in IEC 61850 are the missing definitions for redundant connection of an IED to one or two communication networks. The fact that an increasing number of utilities is requesting fully redundant communication, and not only a single ring, shows the need for higher levels of availability. With the current version of the standard, however, the implementation of a fully redundant communication results in a non-interoperable solution.