wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

59-6 Industrial Communication Systems
FIGURE 59.6
Example for a MMS message.
Table 59.2
Mapping of the Data Models in MMS Services
Objects in IEC 61850
Logical device
Logical node
Data object
Data attribute
Data set
Objects in MMS
Domain
NamedVariable
NamedVariable (structured components)
NamedVariable (structured components)
NamedVariableList
and used by several receivers (subscribers) located in the same subnetwork. It is implemented directly on
the Ethernet Link Layer and supports real-time behavior. It is used, for example, for
• Tripping of switchgears
• Starting of disturbance recorders
• Providing position indications for interlocking
59.4.3 transmission of Sampled Analog Values
The ACSI service called “transmission of sampled analog values” (SAV, defined in IEC 61850-9-2) also
supports a time critical communication, mainly used for the exchange of current and voltage measurements
from high voltage sensors. The characteristics of sampled process values can be transmitted as
broadcast messages in real time from a sending IED (publisher) to receiving IEDs (subscribers). The publisher
writes values together with a time stamp in a sending buffer. After the transmission the subscribers
can read the values from their receiving buffers. This service has the following additional features:
• The transmission over the Ethernet can be in a point-to-point (unicast)-mode or in a multicast-mode.
• The transmission of sampled values is done in an organized and time-controlled way so that the
combined jitter of sampling and transmission is minimized.
• The transmission of the values is controlled by a standardized control-block (SVC—sampled
value control).
© 2011 by Taylor and Francis Group, LLC