Process bus busbar protection — A stepping stone towards digital substation

摘要

The basic building block of a digital substation is IEC 61850 process bus, or the concept of distributed I/O for protection, control and SCADA reporting. Much of the discussion around digital substation has focused on the mechanics of the devices, architectures, and technologies to publish sampled values (SVs) from merging units (MUs) to protective relays. One challenge that has been ignored is the processing of a large amount of data streams for busbar protection. A busbar protection for a reasonably sized transmission substation requires current measurements from multiple bays, bus couplers, and other sources, which requires much more SV data streams than any other situation in the substation domain. Despite the challenge, busbar protection using process bus is simply the proven concept of a distributed busbar protection system, using MUs and SVs as opposed to dedicated bay units and proprietary communications. However, a process bus busbar protection is more than just busbar protection with SVs. It is a novel and complete solution which eliminates conventional busbar protection constraints on the bays' connections, simplifies testing, enhances protection and communications reliability and stability, and facilitates time synchronization without relying on satellite clocks. Integrating process bus simplifies the practical challenges in busbar protection. Redundant protection by connecting a second relay to the network, effortless bay and zone expansion, and reducing limitations on the number of bays and zones. Importantly, a process bus busbar protection application is not limited to just digital substation projects. It can be a standalone busbar protection system, perfect to retrofit conventional busbar protection systems and substations. Once installed, thanks to the standard process bus communication framework architecture, it becomes an excellent stepping stone to convert a conventional substation to a full digital substation.