GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 27)

Power Management Control System
Chapter 2 – Network Design
17
RS-485 IEDs
(31 Max)
Host
Modbus
Concentrator
MC
Commnet IEDs
(up to 32 per Modbus Concentrator,
215 total per RS-485 network)
Figure 10. Network illustrating Modbus Rule 6.
7. A single RS-485 network may have no more than
4000 feet of cable (total cable length, not distance
between IEDs). Figure 11 illustrates this rule.
RS-485 IEDs
(31 Max)
Host
Total Cable Length < 4000 feet
100 ft
300 ft
1500 ft
1500 ft
200 ft 300 ft
Figure 11. Network illustrating Modbus Rule 7.
8. RS-485 repeaters may be used to extend the range
beyond 4000 feet. A single RS-485 repeater may be
used to provide a 4000-foot extension, and each
additional repeater in a sequence extends the range
by another 4000 feet. Figure 12 illustrates this rule.
With 2 Repeaters,
Total Cable Length < 8000 feet
Host
100 ft
200 ft 2500 ft
500 ft 700 ft
4000 ft
R
R
RS-485
Repeaters
Figure 12. Network illustrating Modbus Rule 8.
9. There may be no more than two RS-485 repeaters
between any two RS-485 IEDs. Figure 13 illustrates
this rule.
Correct - Maximum two repeaters between RS-485 IEDs
Incorrect - more than 2 repeaters between RS-485 IEDs
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Figure 13. Network illustrating Modbus Rule 9.
NOTE ON DUAL-PORT RS-485 IEDS:
Several of the Multilin power management IEDs
offer two RS-485 ports on the same IED. Do not
connect both RS-485 ports to a PMCS network.
The
same data are available from both RS-485 ports
and will cause conflicts if the PMCS attempts to
access both ports simultaneously.
However, the Modbus Monitor’s wiring scheme is
slightly different from the Multilin scheme. The
dual-port version of the POWER LEADER
Modbus Monitor MUST be connected to two
separate RS-485 networks. See Rule 10 for details.
10. Modbus Monitors (dual-port version) may not be
wired in any configuration other than the four
shown in Figure 14. Although the Monitor’s RS-485
ports have separate addresses, you may NOT wire
the same Modbus network to both ports. A two-port
Modbus Monitor must be wired to two separate
Modbus networks.
NOTE : For more information on wiring the
POWER LEADER Modbus Monitor, refer to
DEH-027, Modbus Monitor User’s Guide.