Set the CD-port to 9–2LE communication using only LHMI. All other settings are also available
from PCM600.
Factors influencing the accuracy of the sampled values from the merging unit are, for example,
anti aliasing filters, frequency range, step response, truncating, A/D conversion inaccuracy,
time tagging accuracy etc.
In principle, the accuracy of the current and voltage transformers, together with the merging
unit, will have the same quality as the direct input of currents and voltages.
The process bus physical layout can be arranged in several ways, described in Annex B of the
standard, depending on what are the needs for sampled data in a substation.
Engineering
Workstation
Computer HMI
Firewall
VPN
Gateway
Network Control Center
Maintenance Center
AFS 6xx
AFS 6xx
AFS 6xx
AFS 6xx
SAM600
SAM600
SAM600
IEC 61850
FOX615
WAMSSDM600
IET600 PCM600
ITT600
NSD570
Events Printer
Printer
IEC18000011-1-en.vsdx
IEC18000011 V1 EN-US
Figure 200: Example of a station configuration with separated process bus and station
bus
The IED can get analog values simultaneously from a classical CT or VT and from a Merging
Unit, like in this example:
The merging units (MU) are called so because they can gather analog values from one or more
measuring transformers, sample the data and send the data over process bus to other clients
(or subscribers) in the system. Some merging units are able to get data from classical
measuring transformers, others from non-conventional measuring transducers and yet others
can pick up data from both types. The electronic part of a non-conventional measuring
transducer (like a Rogowski coil or a capacitive divider) can represent a MU by itself as long as
it can send sampled data over process bus.
1MRK 511 358-UEN A Section 18
Station communication
411
Application manual
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