ABB Rellon 620 Series, Communication Protocol Manual

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Section 2
IEC 60870-5 overview
RER620 9
Communication Protocol Manual
Section 2 IEC 60870-5 overview
2.1 IEC 60870-5 protocol
The companion standards IEC 60870-5-101 and IEC 60870-5-104 are derived from the
IEC 60870-5 protocol standard definition. It specifies a functional profile for basic
telecontrol tasks.
The IEC 60870-5 protocol stack is based on the reduced reference model called enhanced
performance architecture (EPA). EPA includes three layers of the ISO-OSI model.
• Application layer
• Link layer
• Physical layer
The IEC 60870-5 protocol is described by standard documents.
Table 1: Selected standard provision of the defined telecontrol companion standard
Application layer defines the information elements for structuring application data and the
communication service functions. The user process describes an assortment of basic
application functions.
Link layer defines the frame formats and the transmission procedures of the IEC
communication.
Physical layer defines the hardware-dependent specifications of the IEC 60870-5-101/
IEC 60870-5-104 communication interfaces.
2.2 Transmission
IEC 60870-5-101 allows two alternative transmission procedures, unbalanced and
balanced, to be used in the communication between the controlling station (SCADA
system) and the controlled outstation. IEC 60870-5-104 ignores this setting. After
receiving STARTDT command from the controlling station, the controlled station will
start reporting events immediately to the controlling station without requests.
Selected application functions of IEC 60870-5-5 User process
Selected application information elements of IEC 60870-5-4
Selected application service data units of IEC 60870-5-3
Application layer (7)
Selected link transmission procedures of IEC 60870-5-2
Selected transmission frame formats of IEC 60870-5-1
Link layer (2)
Selected ITU-T recommendations Physical layer (1)