GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 14)

Power Management Control System
Chapter 1 – Introduction
4
Figure 2a. Substation Ethernet and Modbus network.
Figure 3. Modbus and commnet network.
M o dbus
EPM
3720
PLC
90/30
M ultilin
269+
...
M o dbus
C o ncent rator
C o m m n et
C o m m n et d evice s
Ethernet
other
PC
Ethernet
G ate w ay
... ...
H o st
...
Figure 4. Ethernet, Modbus, and commnet network.
Figure 5. Ethernet-based host services Ethernet, Modbus,
and commnet networks.
1–2 Master-Slave Organization
The PMCS in either a Modbus-host or an Ethernet-host
configuration is a master-slave network. The host is
considered to be the master, with the attached networks of
IEDs serving as its slaves.
This relationship means that the communications are
always initiated at the host; an IED will not speak without
being asked to. The master requests information, the slave
replies.
The PMCS DDE Server receives a request from a client
application for some data, perhaps a relay waveform
capture. The Server routes the request to the correct IED,
the IED replies to the Server, and the Server passes the
information back to the client that originally requested it.
For further details, refer to the PMCS Network and Device
Configurator DDE Server User’s Guide
, GEH-6510.