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11.3.2 Communication service
All essential data transmission methods are summarized in Abstract communication service
interface (ACSI); the IED application from communication stack is separated by the ACSI. The
user can map an interface to a communication stack using Specific communication service
mapping (SCSM).
The LN contains data list with their attributes based on their functionality in SAS. A
data has a well-defined structure and information of SAS. The data and attributes of the LN
in a logical device are exchanged by the communication services according to IEC 61850
protocol. The communication services are implemented by SCSM using Ethernet TCP/IP
protocol.
(i) Report for SAS
In the IED, ‘report’ is a method of sending status data, alarm data, measurement data and so
on. Using server-client communication, ‘Report’ is a ‘data set’ transferred from the IED to the
SAS. The ‘reports’ generated by the predefined ‘triggers’ are issued regularly in interval; the
‘reports’ are also generated upon a change in the event. The ‘reports’ are grouped into two
types: (1) Buffered-report-control-block and (2) Unbuffered-report-control-block. Note that the
system achieved by the unbuffered-report-service cannot start an event recover function
during the communication failure.
(ii) GOOSE for peer-to-peer communication
‘Generic Object Oriented Substation Event (GOOSE) ’ is a faster method to transfer the data
in ‘Generic substation event (GSE)’ between IEDs. In all IEDs, multicast GOOSE message is
published from the ‘GOOSE_control_block (GCB)’. The GOOSE communication methods are
grouped into two: (1) GOOSE publish and (2) GOOSE subscribe.
The data structures of the GOOSE are illustrated in Table 11.3-4; they are grouped for
the system (say, SAS) and other logical devices (say, a relay); they are used in the applications
in the SAS and the IED.
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