GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 35)

Power Management Control System
Chapter 2 – Network Design
25
2–9 Multiple RS-485 Networks – Addressing
PMCS supports up to 256 independent Modbus networks.
Regardless of how many RS-485 networks are connected,
the addressing concepts regarding multiple RS-485
networks remain the same. Each RS-485 network is
addressed independently of the others. Thus, Network 1
may have an IED with Modbus address 20, and Network 2
may have an IED with Modbus address 20 without conflict.
The PMCS will be aware that they are different IEDs,
much as the postal system delivering mail realizes that 17
Mulberry Lane in Town A is a different address than 17
Mulberry Lane in Town B.
2–10 System Expansion
Whenever new IEDs are added to the network, be sure to
observe these points:
• Follow the proper installation procedures.
• Ensure that the system configuration rules have been
followed.
• All new IEDs are shipped with the same default
address. To avoid conflicts, change the address of
each new IED immediately upon installation to an
unoccupied address in the PMCS networks.
2–11 Case Studies
Five case studies are provided as examples of how to design
a network based on PMCS. In each case, a fictitious
company called GHO Corp. is installing a power
management system based on PMCS.
In Case One, GHO Corp. has only a few Modbus RTU-
based IEDs that it would like to network to the PMCS
software for remote control and viewing of power
consumption and alarms.
In Case Two, GHO Corp. wishes to expand the Modbus
network it developed in Case One by adding some
commnet IEDs to the network.
In Case Three, GHO Corp. already has an existing
network based on Ethernet and would now like to
integrate a power management system with this network.
GHO Corp. still has only a few Modbus RTU-based IEDs
that it would like to network to the PMCS for remote
control and viewing of power consumption and alarms.
Now, however, it wants the host to be based on Ethernet
rather than Modbus, which requires the use of an
Ethernet Gateway.
In Case Four, GHO Corp. wishes to install a PMCS power
management system using both Modbus- and commnet-
based IEDs, with the host based on Ethernet.
Case Five demonstrates the use of dual-port RS-485 IEDs in
a Modbus network, showing the differences between the
Multilin dual-port IEDs and the POWER LEADER
Modbus Monitor, which also provides two RS-485 ports.
Case Study One
GHO Corp. has assigned its plant engineer, Bill, the task of
designing and installing a simple power management
system. GHO Corp. wishes to use PMCS to monitor and
control several Modbus power management IEDs.
Bill’s first task is an easy one. He must choose a platform
on which the PMCS host will reside. Using the flowchart in
Section 1-1, he makes his decision. There is no existing
Ethernet network in his facility, nor are there any plans for
one. Bill chooses Modbus as his basic platform for the
PMCS.
Next, Bill makes a list of the IEDs that GHO Corp. wants to
include on their PMCS network:
• One PLC 90/30 Programmable Logic Controller for
process control
• Three EPM 3720 Meters for monitoring power
• One Multilin 269+ Motor Relay for motor protection
• One Multilin 565 Feeder Management Relay for
feeder protection
He checks the list of communications protocols in Table 1
and notes that all of the IEDs communicate on Modbus;
because no commnet IEDs are being used, no Modbus
Concentrators are needed. The Modbus IEDs
communicate at different baud rates, though, and Bill
makes a note that they should be placed on separate RS-
485 networks for improved performance.
Bill now turns to his floor layout to see just where the
wiring could be run and how many feet of cable will be
needed. He maps where his IEDs must be located and
where the host PC will sit. He measures the cable runs
required to connect the IEDs to the host PC, keeping in
mind that the wiring rules require him to daisy-chain the
IEDs on each RS-485 network one after another. His floor
layout is shown in Figure 22.