Influence of process bus on performance of power system protection

The development of substation operations under open standards has ensured interoperability among technology manufacturers and has led to system management evolution. Implementing a Process Bus (PB) and its related technologies represents the future of power systems protection. The release of the IEC61850-9-2 sampled values protocol has allowed the replacement of the conventional measurement method by an ethernet-based system at substation yards. This study focuses on the PB implementation effects such as the trip time delay and possible time shift over the protection system performance. The paper points out aspects that should be considered through the engineering process and design, considering the two PB standards, IEC61850-9-2LE and IEC61869-9. A test architecture was composed of a conventional relay, and two PB relays synchronized using the IEEE-1588Precision Time Protocol (PTP). Four tests were carried out, including a software simulation and field-collection data. The two PB standards presented similar results during the tests. The relay signal resampling results in time shifts that should be properly compensated, and the digitalization delays found can occasionally add more than 9 ms in the final trip time and must be considered in protection studies prior to implementation. Otherwise, it can significantly impact on the project of the power system.