Reliability investigations for SA communication architectures based on IEC 61850

The new communication standard IEC 61850 is now introduced to substation automation replacing all wires by serial communication. Based on mainstream communication means like Ethernet it profits from a high flexibility regarding communication architectures. But any solution has to fulfill all reliability requirements resulting from the safety-critical mission of substation automation for a reliable power supply in transmission and distribution grids. To achieve this goal typical types of SA communication architectures are investigated starting from the relevant properties of IEC 61850, using proper reliability definitions and common failure modes. The relevant reliability figures are calculated. Different levels of redundancy, their limits for reliability and impact on the distributed functions are considered. The results clearly indicate what types of architectures have to be applied for the requested reliability of substation automation functions. This includes also function allocation and proposals for amending the standard.