GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 37)

Power Management Control System
Chapter 2 – Network Design
27
point and no two IEDs’ grounds connected (Rule 4,
Section 2-4).
Bill assigns a Modbus address to each IED. He then sets
communication speeds and functional and protective
parameters according to the instructions in each user
manual.
Bill installs the PMCS software at the host PC and
configures IED addresses at the host to match the
addresses assigned to each on the network.
When all connections have been made and the IEDs and
software are appropriately configured, Bill applies power
to the system and runs tests to assure that everything is
functioning properly.
If any difficulties are encountered, Bill refers to the
trouble-shooting guide in Chapter 4.
Case Two
Case Two begins where Case One left off. The Modbus
network is in place and GHO Corp. has been so pleased
with their new PMCS system that they now wish to tie in a
second building (Facility Two) and add several additional
power management IEDs. However, the IEDs they wish to
add are all commnet IEDs.
The host platform is based on Modbus, with a multi-port
RS-485 interface card providing the connection to the
networks. Knowing the host platform and its currently
attached IEDs, Bill makes a list of the IEDs that GHO
Corp. want to add to their PMCS network. His list of
additional IEDs is:
• Six Enhanced MicroVersaTrip trip units for
equipment protection
• Three POWER LEADER Meters for waveform
capture
• One POWER LEADER EPM
• One POWER LEADER MDP Overcurrent Relay
• One Spectra Electronic Control Module
Commnet IEDs require Modbus Concentrators to be
recognized by the PMCS. Bill has nine commnet IEDs to
connect, so he will need only one Modbus Concentrator
(each Concentrator supports up to 32 commnet IEDs).
However, with some of the commnet IEDs located in
Facility Two, well beyond the 1000-foot segment limit, Bill
realizes that he must either locate the Modbus
Concentrator in Facility 1 and run several very long
commnet segments using POWER LEADER Repeaters to
span the long runs or place a Modbus Concentrator in
Facility Two and extend his RS-485 network over to Facility
Two with RS-485 repeaters. Bill decides that it will be
easier and more cost effective to run a single long RS-485
segment with a pair of RS-485 repeaters than to extend six
commnet segments. An added benefit: each repeater uses
optical isolation between its incoming and outgoing lines,
eliminating harmful ground loops that can result when
the ground potential between two structures is different.
For even greater electrical isolation Bill could have used an
optical fiber link between the two remote locations.
Bill turns to his floor layout, to see just where the wiring
could be run and how much distance it must cover. He
knows where his host PC is located and realizes that he will
have to interrupt the Modbus network at one or more
locations to insert Modbus Concentrators to support his
commnet IEDs. He maps where his IEDs must be located
and, based on this information, where the Concentrators
will be mounted. Next he plans the commnet segments
and measures the cable runs required for each segment to
connect the IEDs to the Modbus Concentrator, keeping in
mind that the commnet rules require him to daisy-chain
the IEDs one after another (unless he uses a
Junction/Outlet box). His floor layout is shown in Figure
24.