Design and operation of the IEC61850 9–2 process bus used for the protection system

The digital substation and the implementation of IEC61850 are fundamental to the future of protection relays. The IEC61850 standard, "Communication Networks and Systems in Substation", provides the basis for the communication system for the digital sub-station\´s protection and control schemes. Section 9–2 defines the Ethernet based communication network providing data transfer between primary equipment and bay level IEDs, the process bus. This paper describes the background for the choice of bus architecture for the process bus for use in an EHV transmission sub-station. It reports on the results of performance tests on a feeder protection scheme using both an IEC 61850 and a conventional relay. Further tests have examined the performance of the IEC61850 relay when the data transfer traffic on the process bus exceeds its capability and data packets are therefore lost.