Advanced networks for distributed measurement in substation automation systems

The adoption of IEC 61850 in the deployment of Substation Automation System opens new scenarios to system design. The presence of a communication infrastructure connecting Intelligent Electronic Device (IED), sensors and protections may suggest the development of distribute measurement devices, where the sampling of the physical quantities and the elaboration of the sampled value could be performed by different physical devices. Nevertheless, such architecture is based on an ideal communication infrastructure, which can transfer the information among the distributed devices without affecting the measurement performance. On the contrary a real network infrastructure could suffer from several failure conditions, mainly to the harsh environment of substations where the installed network devices are not periodically replaced. In the following paper, the effects of network faults on a distributed measurement system in electrical substations are considered. The behavior of network infrastructure and the quality of the service offered in the case of the most common network failures has been analyzed using a simulation environment. The results demonstrate that the commonly adopted Rapid Spanning Tree Protocol (RSTP) is not suitable for the most demanding measurement applications due to the loss of measurement samples during the network reconfiguration time (up to 200 ms). On the contrary, more advanced redundancy protocols, like Parallel Redundancy Protocol (PRP), are able to satisfy also the most strict availability requirements, as suggested by the simulation results.