GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 41)

Power Management Control System
Chapter 2 – Network Design
31
protector at the hub on the incoming line from the EPM
7700 IED to shield the rest of the network from potentially
damaging transients.
Because he has only six Modbus IEDs (five IEDs and the
Modbus Concentrator) and 12 commnet IEDs to connect,
he requires only one RS-485 network (each RS-485
network accommodates up to 31 Modbus IEDs and up to
215 commnet IEDs). However, because his Modbus IEDs
communicate at several different baud rates, Bill decides
to assign them to different RS-485 networks to achieve
greater system performance.
He also notes that each RS-485 network must be properly
terminated at each end. He must keep the RS-485 cable
length of each RS-485 network under 4000 feet, unless he
uses RS-485 repeaters, as on Network 3, to span the 3,500
feet to Facility 2.
The commnet rules are also easy to comply with. Each of
the commnet segments must be kept under 1000 feet,
unless repeaters are used to extend the range of the
segments, as is required to reach the commnet IEDs in
Facility 3. Each commnet segment is limited to four
commnet IEDs, and no segment may have more than one
waveform capture meter (POWER LEADER Meter). Bill
makes sure that his POWER LEADER Meters are limited
to one per segment.
Bill now 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
host PC will sit. He then measures the cable runs required
to connect the IEDs to the host PC, keeping in mind that
the RS-485 rules require him to daisy-chain the Modbus
IEDs one after another from the Ethernet Gateway and the
commnet IEDs (four per segment) from the Modbus
Concentrator. His floor layout is shown in Figure 26.
The RS-485 cabling is less than 4000 feet for each of the
RS-485 networks, except for Network 3, where RS-485
repeaters are used to bridge the 3,500 feet to Facility Two.
Each of the commnet segments requires less than 1000 feet
of cable, except for segment three, where POWER
LEADER Repeaters are used to span the 5000 feet to
Facility Three. The wiring rules are satisfied.
Bill selects Modbus addresses for the Modbus IEDs and
Modbus equivalent addresses for the commnet IEDs, using
the worksheets in the back of the Modbus Concentrator User
Guide
(GEH-6491), and records them for future reference.
Bill’s address chart, found in Table 11, follows the floor
layout.
Multilin 269
Modbus
Concentrator
600'
600'
Assembly
Line
Area
Milling Area
Machining Area
Lathe Area
Segment 5 Commnet Segment 1
POWER
LEADER
Meter
Network 1 -
9600 baud Network 3 - 19.2 kbaud
PLEPM
EMVT
Long-range
RS485 cable run
3500 feet
Terminating
Resistor
RS485 repeater
MDP POWER LEADER
Meter
Segment 4
Facility Three
Segment 2
ECM
Terminating
Resistor
EMVT
Facility Two
POW ER
LEADER
Meter
RS485 repeater
POWER LEADER Repeater
Segment 3
POWER
LEADER
Repeater Long-range commnet cable run
5000 feet
Bill's Office
EMVT
EMVT EMVT
650'
EMVT
550'
100'
Multilin 565
Feeder Management Relay
at main power feed
PLC 90/30
Programmable Logic Controller
EPM 3720
EPM 7700
EPM 3720
Network 2 -
2400 baud
Ethernet
Gateway
RS-485 networks terminated
at Ethernet Gateway
Ethernet Ethernet
Hub
Ethernet
Ethernet connection to EPM 7700 is surge-protected
Ethernet connection
to corporate LAN
Figure 26. Floor layout for Case Four.