Saturday, January 18, 2014

Is IEC 61850 creating Opportunities for a Revolution?

Don’t ask for it – you may get it!

I read the other day a paper on IEC 61850 (written by known experts) that summarizes in the opening sentence: “IEC 61850 is an approved international standard for communications in substations that is creating opportunities for a revolution in the world of electric power systems protection and control.”

According to Wikipedia “A revolution (from the Latin revolutio, "a turn around") is a fundamental change in power or organizational structures that takes place in a relatively short period of time.”

The core parts of the standard have been published some 10 years ago. The crucial underlying technology is even older. I have not yet seen many opportunities for a revolution in the communication – yes, some new communication possibilities have been implemented. The introduction of the standard is more a marathon than a sprint! There are very good new features related to engineering and configuration (SCL) – their application will even take much longer then the use of Ethernet, TCP/IP, MMS, ACSI, … Anyway, the standard communication defined in IEC 61850-7-2 and –8-1 are excellent.

Let’s have a look on the communication “revolution”. The first figure depicts a very traditional way to exchange status changes, measurements and calculated analogue values, counted values, and so on: The destination (master or client) sends request messages to the source (slave, server) and receives the requested values. The request may be sent cyclically or at any time. The rate of these request-response transactions (controlled by the caller) has a crucial impact on the bandwidth use and real-time behavior.


Depending on the needs there could be a huge difference in sending requests more or less often. Read some hints on reporting versus polling.

Now let’s have a look at the telecontrol protocols IEC 60870-5-104 and DNP3 (as well known and used examples). They offer additional possibilities: receiving cyclic reports from the source, receiving event driven reports (!) and cyclic reports of analogue values initiated by the source.


Finally we check the standard communication defined in IEC 61850. IEC 61850 offers all the above discussed possibilities – it has some optimization build in: DataSets (referring to a list of values). The crucial add-on is the GOOSE messaging and Sampled Value exchange:


GOOSE is a combination of event-driven information exchange (event will be sent immediately) and cyclic transmission (event will be repeated immediately, a little bit later, … any finally in a long cycle). Sampled values comprise an exchange of values that are taken in a time-synchronized fashion. The communication does not need to transmit cyclically – the values taken at the same instance of time are used for calculation.

So, the most crucial new communication services defined in IEC 61850 are GOOSE and Sampled Values – and the possibility to configure the behavior of reporting, GOOSE and sampled values through SCL and by online services.

There is one additional service in IEC 61850 that is quite new: Logging.

In many applications where IEC 61850 is used we see more of a slow evolution – not a revolution. I guess the power industry can not easily be revolutionized. That is a good situation – without that we would have to sit more often in the dark.

Smart Grids is a 19th century invention. The evolution that happened during this very long period of time is what has brought us today’s secure and safe electric power delivery. Note: Haste produces Waste! Take your time … and use IEC 61850 when it’s time to do so … not earlier! The evolution has to start in the heads by good education provided by people that understand that utilities don’t want to get a revolution at all.

I hope we will not get a revolution!

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