Many of us in the power sector are aware that IEC 61850 is a good starting reference when it comes to digital substation communications. After all, the descriptive title of this standard is: Communication networks and systems for power utility automation. The standard does indeed address communications. It provides protocols for exchanging information between relays using high speed communications without hard wired connections using GOOSE (Generic Object Oriented Substation Event ) messaging, Manufacturing Message Specification (MMS), Sampled Measured Values (SMV) schemes and other protocols.
However, IEC61850 also provides standardized substation configuration and naming conventions that provide object oriented comprehensive, vendor-agnostic models for functions /data development; and IEC61850 provides conformance testing and system specifications that speed design and testing to minimize the risk of startup and later consistency issues for power systems. Take five minutes to review this fast paced video of how IEC61850 lays the foundation for all things digital in the power sector:
If digital intelligent electronic devices (IEDs) and systems are new to you, it is easy to get hung up on all the communication protocols that may be involved. Learn what those pesky acronyms stand for and it will begin to make some sense. Here are a few to get you started.
MMS-Manufacturing Message Specification is an application layer standard (ISO 9506) designed to support the transfer of process data and supervisory control information between programmable devices or computer systems. In digital substation applications it is used for the transfer of non-time critical data and reports using the station bus.
GOOSE-Generic Object Oriented Substation Events is a controlled model messaging system applied for SAS (Substation Automation System) control and monitoring of primary equipment and IED status. GOOSE messaging is also used for status interactions between IEDs, including protection relays. Transmitted data is arranged in a data set and must be transmitted within a time period of 4 milliseconds. This system is used for time critical messaging at the process bus level in digital substations and anywhere else high speed multicast messaging is needed.
SMV-Sampled Measured Values is a method for transmitting digitized instantaneous measured values of power system quantities, mainly primary currents and voltages. It enables sharing input/output signals from IEDS and can be used for multicast and point-to-point messaging. SMV messaging is also used for time critical data transfer in digital substations.
GSSE-Generic Substation State Events is a derivative of the Generic Substation Events (GSE) control model. Like the GOOSE model, GSSE provides a reliable, high speed mechanism for transferring event data over networks. However, only status data can be exchanged through GSSE. The GSSE format is simpler than GOOSE, so it may be handled faster in some devices.
If you want to learn more about digital communications, digital substations and the basics of IEC 61850 that will transcend the power industry’s digital future, look up this detailed PDF from the Illinois Security Lab: http://seclab.illinois.edu/wp-content/uploads/2011/03/iec61850-intro.pdf.
