Saturday, March 2, 2019

IEC TC 57 Just Published Draft IEC 61850-90-20 On Redundancy

IEC TC 57 just published the first Draft IEC 61850-90-20 on System Redundancy:

IEC TR 61850-90-20 ED1
Communication networks and systems for power utility automation –
Part 90-20: Guideline to redundancy systems

Excerpt from the Introduction:

"The paper “CIGRE B5-109: Redundancy challenges on IEC 61850 systems and Migration
Paths for IEC 61850 Substation Communication Networks” introduce redundancy concepts as
“Device redundancy of substation control units may be required in order to increase the availability of the substation automation system at the station level. System level redundancy is achieved by hot-hot or hot-standby configuration of duplicated station units that need to exchange information to ensure data consistency as well as coordinated and safe operation.
IEC 61850 communications in redundant configuration of duplicated clients faces challenges how to ensure that database in both central station control units are synchronized and that no events are lost during the switchover from the primary to secondary IEC 61850 client.”
A proposed redundancy system consists of two IED entities forming a logic IED. One or more lower level IEDs, e.g. merging units or circuit breaker, delivering the input data for the IED entities and getting results from the IED entities. One or more higher level clients receives output data from the IED entities for supervision or HMI.
Additionally, a higher level IED might exist, which supervises the state of the redundant system. In this context this concerns especially the state of the IED entities, so that a failed IED can be detected and repaired before the second IED fails.
The communication between the redundant system application and the lower level IEDs takes place with IEC 61850, mainly based on IEC 61850-8-1(MMS) reporting and commands, for time critical functions with IEC 61850-8-1(GOOSE) and IEC 61850-9-2(SV).
The communication to station level clients based on IEC 61850 is typically MMS based for supervision, commands and settings configuration changes. Since MMS is acknowledged service, server and client are aware of each other and the client supervises the servers. If both redundant system IEDs are hot, the client might select which of them it takes for executing a service request."

The TC57 P-members are invited to submit comments to this draft by 2019-03-29 at the latest.

Please note:
The application domains that need redundant systems may be crucial (for some high voltage systems) but may not be applicable for most systems in the energy delivery domain. This document is really of interest for a small, special group of experts ... not everybody interested in using IEC 61850 for exchanging some signals may need to check that draft document.
One challenge with IEC 61850 is: Which subset out of a big standard series do I need to understand for my application - that means: YOU HAVE TO KNOW YOUR APPLICATION !!

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