IEC 61850 process bus application in Energinet, Denmark

Substation automation solutions have been progressively migrating to higher levels of digital technology over the past decade or more, as IEC 61850 has gained ground globally. The technology available today makes fully digital substations feasible - at the process level as well as the station level. Digital substation implementation allows the lifetime total cost of ownership of the substation to be reduced. This paper details a digital substation project implementation in Energinet, Denmark related to the integration of renewable generation into the country´s 400 KV grid. Non-conventional instrument transformers are utilized in the project, and the paper describes the considerations in selecting, testing and commissioning the primary equipment, and the benefits associated with the technology. The project utilises current differential protection working on IEC 61850 sampled values to identify faults in specific sections of the 400KV feeders and adapt the overall protection scheme. Feeder differential schemes are among the more complex protection applications, and the paper discusses the adaptation of the protection to IEC 61850 sampled values, taking into account greenfield and refurbishment projects. The paper discusses the integration of network, protection system architecture, merging unit performance and synchronising of sampled data for current differential protection. The test results are presented to show the stability and operation of the protection scheme. Furthermore, the Energinet project shows the increasing confidence in the application of digital substations within Europe. This is essential at this network voltage level, where cost savings and health & safety are of paramount importance. As such, this project is a valuable return on experience for other utilities to follow in the same manner for both new and refurbishment projects.