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

IEC 61850 for Distributed Energy Resources 59-5
Client-server
comm.
GetDirectory
GetDataObjectDefinition
GetDataValues/SetDataValues
ReportSettings
Abstract communication services (ACSI)
GOOSE
Sampled analog
values (SAV)
Clock
synchronization
Specific communication service mapping (SCSM)
MMS
InformationReport
Read/Write
GetVarAcessAttributess
GetNameList
TCP
IP
Ethernet link layer
Ethernet physical layer with priority tagging
SNTP
UDP
IP
FIGURE 59.5
Comparison between ACSI and SCSM.
59.4.1 Client/Server Communication
The most important ACSI services for distributed energy resources are the client-server communication
services. They include services such as the following:
• GetDirectory: When a client wants to communicate with another IED it can retrieve a complete
list of the names of all accessible objects in an IED, which are LDs, LNs, DOs, and data
attributes.
• GetDataObjectDefinition: A client can retrieve the data types for all objects.
• GetDataValues, SetDataValues: The values of the objects can be read and written.
• Reporting: It allows an event driven data exchange of packed values between a server and a client.
The values can be transmitted by an IED either immediately or after some buffer time.
• Logging: The server provides the possibility to archive data for later retrieval by clients.
According to the actual state of the IEC 61850 standard, the client/server communication services
have to be mapped to the Manufacturing Message Specification (MMS)-protocol that is based on
Ethernet and TCP/IP (Figure 59.6). The MMS standard originally was developed for the communication
between manufacturing devices like numerically controlled machine tools, transport systems and
supervisory control and data acquisition (SCADA) systems. MMS defines a structure for the messages
required to control and monitor the devices. It is not concerned with the way the messages are transferred
between devices over a network. For that Ethernet and TCP/IP is used. The data objects in the IEC
61850 are mapped to MMS as presented in Table 59.2.
The mapping of some ACSI-services to MMS is already shown in Figure 59.5. Figure 59.6 shows a
detailed example for the concrete message encoding of a GetDirectory ACSI-service to a GetNameList
message of the MMS protocol.
59.4.2 GOOSE
Another ACSI service specified by the IEC 61850-standard is the so called Generic Object Oriented
Substation Event (GOOSE). It is a mechanism for the fast transmission of events, such as commands,
alarms, and indications. A single GOOSE broadcast-message sent by an IED (publisher) can be received
© 2011 by Taylor and Francis Group, LLC