GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 39)

Power Management Control System
Chapter 2 – Network Design
29
Commnet wiring requires Belden 8719 cable. Bill installs
the IEDs according to the instructions in each user
manual. He wires each commnet segment in daisy-chain
fashion, one IED to the next, being sure to ground the
shield at the Modbus Concentrator only.
Bill then sets local addresses on the IEDs in accordance
with the addressing rules in Section 2–6. He sets
communication speeds and parameters according to the
instructions in each user manual.
Bill installs the PMCS software at the host PC and
configures the IED addresses.
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 Three
In Case Three, GHO Corp. has an existing Ethernet
network installed and would now like to add power
management capabilities with PMCS. Once again, plant
engineer Bill has been given the task of designing and
installing this system.
As before, Bill’s first task is to choose a platform on which
the PMCS host will reside. Using the flowchart in Section
1-1, he decides that the PMCS will reside on Ethernet,
requiring one or more Ethernet Gateways to communicate
with the RS-485 networks.
Next, Bill makes a list of the IEDs that GHO Corp. needs to
support on their PMCS network. The IED list is the same
as in Case One:
• One PLC 90/30 Programmable Logic Controller for
process control
• One EPM 3720 Meter for monitoring power
• One Multilin SR745 Transformer Management Relay
• One Multilin SR469 Motor Management Relay
• One Multilin 269+ Motor Relay for motor protection
• One Multilin 565 Feeder Management Relay for
feeder protection
The list of communication protocols in Table 1 shows that
all the IEDs communicate on Modbus; because no
commnet IEDs are being used, no Modbus Concentrators
are needed. However, because the PMCS will be operating
on Ethernet, he will need to use an Ethernet Gateway to
relay communications between the host and the Modbus
networks. Table 1 also indicates that the Modbus IEDs
have different communication speeds. For performance
reasons, Bill decides to break the IEDs off to independent
networks rather than connect all of them to the same RS-
485 network. The Ethernet Gateway offers four RS-485
ports, so using more than one port poses no additional
cost burdens or configuration concerns.
Bill turns to his floor layout, to see just where the wiring
could be run and how much distance it must cover. He
maps where his IEDs must be located and where the
Ethernet Gateway will sit. He then measures the cable runs
required to connect the IEDs to the Ethernet Gateway,
keeping in mind that the RS-485 rules require him to
daisy-chain the IEDs one after another. His floor layout is
shown in Figure 25.
Bill's Office
GHO Corp Machine Shop -
network wiring diagram
350'
550'
150'
Terminating
Resistors
Multilin 565
Feeder Management Relay
PLC 90/30
Programmable Logic Controller
EPM 3720
Electronic Power Meter
Multilin SR745
Transform er
Managem ent Relay
Multilin 269+
Motor Relay
600'
600'
Assembly Line Area
Milling Area
Machining Area
Lathe Area
Network 4 - 19.2 kbaud
Network 3 - 19.2 kbaud
N
et
w
or
k
2
- 2
40
0
ba
ud
Ethernet
Ethernet
Gateway 150'
Network 1 -
9600 baud
RS485 networks terminated
at Ethernet Gateway
Multilin SR469
Motor Management Relay
Figure 25. Floor layout for Case Three.
Next, Bill checks Table 2 for the Modbus wiring rules and
Table 3 for the Ethernet wiring rules.
He notes that he must properly terminate the RS-485
network at each end and that he must keep his total RS-
485 cable length under 4000 feet, unless he invests in RS-
485 repeaters or puts the IEDs on separate RS-485
networks, which may run in different directions and
effectively increase his range.
His cabling limits are satisfied, so Bill selects Modbus
addresses for the IEDs, and records them for future
reference. His address chart is shown in Table 10.