The IDS company based in Ettlingen (Germany) offers a gateway to collect data from many underlying protocols and converts them into IEC 61850 Models for the communication with control centers. They wrote in a recent publication that the classical RTU protocols IEC 60870-5-101 and –104 are phase-out solutions for the communication with control centers. One crucial issue they highlight is the semantic information models and self-description services defined in IEC 61850.
The same company was a very strong supporter for using IEC 60870-5-101 and –104 for the communication with control centers – and partly within substations. What I see these days: More and more people are changing their mind!
The protocol gateway (which is a server) uses for the uplink to the control center IEC 61850 information objects and web services according to IEC 61400-25-4 Annex A for the protocol. This combination (IEC 61850 models and IEC 61400-25-4 mappings) is technically feasible. Formally it is not defined in any standard!
That is why the gateway (server) cannot interoperate with any IEC 61850 client. It is a product that can communicate with a client according to IEC 61400-25-4 Annex A only.
The first reason they provided why they did not use MMS is as follows: MMS would require to have permanent TCP and MMS connections maintained! That is true for substation automation, where short reaction times for crucial spontaneous event reports are required. If the required reaction is in the seconds, there is no reason why a permanent connection should be required! MMS does not require permanent connections! A MMS client can close the connection as soon as a service is completed.
Click HERE for the paper published in the etz magazine [German only].
It is also important to know that (to my knowledge) most vendors implementing IEC 61400-25 are using the mapping according to IEC 61400-25-4 Annex C (MMS, IEC 61850-8-1): Bachmann, Beckhoff, Ingeteam, Siemens, …
Finally: a new work item has been proposed to IEC TC 57 (home of IEC 61850) to standardize a web service mapping as IEC 61850-8-2. The question is now: Which solution should be chosen or developed? Three candidates are already discussed and proposed for further investigation:
1. DPWS (Device Profile Web Services)
2. OPC UA WS
3. IEC 61400-25-4 Annex A (as a starting point)
Nobody knows which solution will finally be standardized for IEC 61850 and how long it will take. There may be additional candidates proposed during the official ballot on the new work item once it is out for ballot … may be by end of 2011. Hopefully we will see a single solution being published in 8-2. Nobody knows.
Having multiple standards for the mappings means: split the market in non-interoperability domains!
Click HERE for a further a discussion on web services.
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