GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 36)

Power Management Control System
Chapter 2 – Network Design
26
Bill's Office
GHO Corp Machine Shop -
network wiring diagram
350'
550'
200'
300'
Terminating
Resistors
Multilin 565
Feeder Management Relay
PLC 90/30
Programmable Logic Controller
EPM 3720
Electronic Power Meter
EPM 3720
Electronic Power Meter
EPM 3720
Electronic Power Meter
Multilin 269+
Motor Relay
350'
550'
Main power feed
Assembly Line Area
Milling Area
Machining Area
Lathe Area
Figure 22. Floor layout for Case One.
Bill’s calculates his total cable length at 2300 feet, well
short of the 4000-foot limit.
Next, Bill checks Table 2 for the Modbus wiring rules.
Proper termination is required at each end of the network,
and is provided at the RS-485 card by attaching jumpers to
the correct pins (see RS-485 card user manual). The
appropriate terminating resistors must be used at the
opposite end of each RS-485 network, per Section 2–4, rule
3.
His cable length is well under the 4000-foot limit, so no
repeaters will be needed.
Because he has only six IEDs to connect, only one RS-485
network is required, and thus an RS-232/RS-485 converter
would do the job. However, he considers the performance
recommendations given in Section 2-6 and, remembering
his earlier note about the different baud rates of his
Modbus IEDs, he decides to distribute the IEDs across four
ports of an RS-485 network card, so that he can place IEDs
with matching baud rates on the same RS-485 network.
The system redesigned for optimum performance is shown
in Figure 23.
Bill's Office
GHO Corp Machine Shop -
network wiring diagram
350'
550'
100'
Terminating
Resistors
Multilin 565
Feeder Management Relay
at main power feed
PLC 90/30
Programmable Logic Controller
EPM 3720
Electronic Power Meter
EPM 3720
Electronic Power Meter
EPM 3720
Electronic Power Meter
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
N
et
w
or
k
1
- 9
60
0
ba
ud
RS485 networks
terminated at host PC
Figure 23. Redesigned layout for Case One.
Confident that his new design will provide maximum
performance, and with his wiring requirements and limits
met, Bill moves on to select Modbus addresses for the IEDs.
He checks Section 2-7 and sees that he can assign his IEDs
any Modbus address between 1 and 247. He selects
addresses and records them for future reference. The
address chart is shown in Table 8.
IED Type Physical Location Modbus Address
PLC 90/30 Assembly line 01
EPM 3720 Milling 02
EPM 3720 Lathe area 03
EPM 3720 Machining 04
Multilin 269+ Assembly line 05
Multilin 565 Power intake area 06
Table 8. IED Addresses for Case One.
Chapter 3 provides Bill with physical wiring requirements
and rules. He finds that he’ll have to use Belden 3074F
cable, readily available. He also locates the correct
terminating resistors at both ends of each RS-485 network.
He installs the IEDs according to the instructions in the
user manual for each IED. He then makes connections to
the RS-485 communications cable in daisy-chain fashion,
one IED to the next, terminated at each end of each RS-
485 network, double-checking his wiring against the
example provided in Section 2–4.
He must also bear in mind proper shield-grounding
considerations – each RS-485 IED grounded at only one