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Glossary
NACK
Negative acknowledgment
Navigation Window
Left area of the project window, which visualizes the names and symbols of all containers of a project in the
form of a hierarchical tree structure.
Object
Each element of a project structure is designated as an object in DIGSI 5.
Object Property
Each object has properties. These can on the one hand be general properties that are common to several
objects. Otherwise, an object can also have object-specific properties.
Offline
If there is no communication connection between a PC program (for example, configuration program) and a
runtime application (for example, a PC application), the PC program is offline. The PC program executes in
Offline mode.
Online
If there is a communication connection between a PC program (for example, configuration program) and a
runtime application (for example, a PC application), the PC program is online. The PC program executes in
Online mode.
Optical Switch Module
An Optical Switch Module (OSM) is a process for switching over switches in Ethernet networks that are ring-
shaped in structure. OSM is a proprietary process from Siemens, which later became standard under the term
MRP. OSM is integrated in the optical Ethernet module EN100-O. OSM is hardly used in IEC 61850 networks.
RSTP is used there, this having become established as an international standard.
OSM
Optical Switch Module
Output data/Output direction
Data is sent from the protocol master to the protocol slave.
Parallel Redundancy Protocol
Parallel Redundancy Protocol (PRP) is a redundancy protocol for Ethernet networks that is specified in IEC
62439-3. Unlike conventional redundancy procedures, such as RSTP (Rapid Spanning Tree Protocol, IEEE
802.1D-2004), PRP offers uninterruptible switching, which avoids any down time in the event of a fault, and
thus the highest availability.
PRP is based on the following approach: The redundancy procedure is generated in the end device itself. The
principle is simple: The redundant end device has 2 Ethernet interfaces with the same address (DAN, Double
Attached Node). Now, the same indication is sent twice, in the case of PRP (parallel) to 2 separate networks,
and uniquely marks both with a sequence number. The recipient takes the information that it receives first,
stores its ID based on the source address and the sequence number in a duplicate filter and thus recognizes
the 2nd, redundant information. This redundant information is then discarded. If the 1st indication is missing,
the 2nd indication with the same content comes via the other network. This redundancy avoids a switching
procedure in the network and is thus interruption-free. The end device forwards no messages to the other
network. Since the process is realized in the Ethernet layer (same MAC address), it is transparent and usable
for all Ethernet payload protocols (IEC 61850, DNP, other TCP/IP based protocols). In addition, it is possible to
use one of the 2 networks for the transmission of non-redundant messages.
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SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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