ICD Documents for programmable and modular IEDs

If you have a modular 61850 product that can be shipped with a variable number of I/O cards, this may have a number of consequences:

1. The number of LNs this product can support depends on the hardware configuration.
2. LNs use shared resources, so if the user adds an LN of one type, he may not be able to add an LN of another type.

Be aware: everything is limited!

These tradeoffs are complex. If you produced an ICD file with the maximum number of LNs of every type your IED supports, for the maximum hardware configuration, the resulting file would be ridiculously large and unwieldy.

How to solve this issue?

All IEDs with a fixed functionality have definitely an easy to build icd file.

IEDs that are programmable or that are modular with one or more I/O cards are different. When the IED comes from the factory, you do not know what the application will be – so you do not know the information model and therefore you cannot provide an icd file for an application running on an IED.

What you could do is to provide an icd file that specifies the communication capabilities (services) and the DataTypeTemplates with all LNTypes that can be instantiated in that IED.

Once it is decided which functions (and LNs) will be running on a particular IED (with one, two, … or five I/O cards), then the IED Configurator (as a manufacturer-specific tool) can create the “final” ICD file for a particular function.

The icd must have exactly one IED section. I would put the LN instances of LLN0 and LPHD in the IED section. The other (functional LNs) would be added be the IED Configurator later … when the number of I/O cards etc are known and selected.

Why do we need Single Point and Double Point Status?

The Single Point signals and Double Point signals for Status monitoring of e.g. circuit breaker switch positions in substations are quite special in process control systems. The basic definitions have been made in fifties of the last century - when remote monitoring was realized with electro-mechanical relays, contacts, wires and relay inputs.

The most simplest approach was to use a single contact to signal a switch position: 110 V on the input contact = Switch closed; no voltage = Switch open. This single contact is called "a Single Point Signal":

This solution was not very safe. Think of broken wire that was not detected. Or of a contact that was not closed for a long time. After that time the contact may have been corroded so that after closing the contact mechanically there is no electrical contact! The receiving device would not be informed that the switch has been closed!

Engineers found solutions to solve the problem: They invented the "Double Point Signal":

Single Point and Double Point Data Types are still in use in serial communication systems like DNP3, IEC 60870-5-104 or IEC 61850. The IEC 61850-7-3 defines these types -- so-called Common Data Classes (CDC).

The reason for Double Point Status in serial communication systems (like the IEC 61850-7-3 CDC DPS) is quite different: the two bits for the representation of "open" and "close" make the status message secure. A single bit error does not cause a wrong interpretation of the value! The value will not be valid anymore.

More details on the basic modeling approach of process information and information exchange is provided in the comprehensive and neutral seminars and training classes of NettedAutomation GmbH (details). Now is the time to get more education.

Phoenix Contact entwickelt IEC61850-Komponenten

Harald Grewe (Produktmanager IP67-I/O-Systeme bei der Phoenix Contact Electronics GmbH) berichtet am 11.09.2008:

"... Als langjähriger Partner vieler Energieversorgungs-Unternehmen setzt Phoenix Contact die Anforderungen der IEC61850 in entsprechende Komponenten um. Die Kombination aus umfassenden Branchenkenntnissen und einem tief greifenden Know-how in puncto Kommunikationstechniken wird zu ausgereiften Geräten führen, die zur Erhöhung der Produktivität der Schaltanlagen beitragen. ..."

Kompletter Beitrag im "Maschinenmarkt" ...