GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 29)

Power Management Control System
Chapter 2 – Network Design
19
2–6 Commnet Wiring Rules – Diagrams
POWER LEADER commnet IEDs may be integrated into
PMCS through the use of the POWER LEADER Modbus
Concentrator, which collects data from commnet IEDs
and communicates that data across the RS-485 network.
Each Modbus Concentrator supports up to eight commnet
segments. Each commnet segment may accommodate up
to four commnet IEDs. The following are the basic rules to
ensure proper network operation for POWER LEADER
commnet IEDs. Note that these rules apply only to
individual commnet segments of a POWER LEADER
Modbus Concentrator, not to the RS-485 network.
1. Each Modbus Concentrator supports up to eight
commnet segments. Each commnet segment may
support up to four commnet IEDs, only one of
which may be a waveform-capturing meter. POWER
LEADER Repeaters and Junction/Outlet Boxes are
not counted as commnet IEDs. Figure 15 illustrates
this rule.
Modbus
Concentrator
4 commnet IEDs/segment
max
Figure 15. Network illustrating commnet Rule 1.
2. A commnet segment may have no more than 1000
feet of cable between the Modbus Concentrator and
the final IED on a segment. (Repeaters may be used
to extend this range; see Rule 3.) Figure 16
illustrates this rule.
Modbus
Concentrator
200
ft
300 ft
200
ft
200
ft
Max length of a commnet segment < 1000 feet
Figure 16. Network illustrating commnet Rule 2.
3. The maximum communication range of commnet
IEDs (including the Modbus Concentrator’s
commnet ports) is 1000 feet, after which its signal
degrades and the danger of errors rises to an
unacceptable level. The Repeater regenerates a
signal to its original strength, allowing it to travel up
to another 1000 feet. Thus, each Repeater can add
up to 1000 feet of range to the commnet segment.
For example, a segment containing a single
Repeater may have no more than 2000 feet of total
cable length. No more than 1000 feet of cable are
permitted between the Modbus Concentrator and
the first Repeater or between the Repeater and the
last IED on the segment. Figure 17 illustrates this
rule.
CAUTION: In no case may there be more than
1000 feet of cable between any two commnet
IEDs other than Repeaters. At ranges over 1000
feet, commnet signals become degraded and
communication errors may result.
Modbus
Concentrator
600
ft
400 ft
200
ft
600
ft
Max length of a commnet segment
with one Repeater < 2000 feet
200
ft
R
Figure 17. Network illustrating commnet Rule 3.
4. Long-distance cable runs may be built by placing two
Repeaters adjacent to one another in the segment. A
pair of adjacent Repeaters has a range of up to 6000
feet of cable. Figure 18 illustrates this rule.
Modbus
Concentrator
600
ft
400 ft
R R
6000
ft
600
ft
Max length of a commnet segment
with two Repeaters < 8000 feet
200
ft
200
ft
4000
ft
1000 ft
6000
ft
Ma x len gth of a com m ne t segm ent
with th ree R e pea ter s < 12 000 fe et
(note: only o ne othe r IE D m ay be use d o n
a co m m n et segm ent w ith th ree rep eaters)
R R R
1000
ft
Figure 18. Network illustrating commnet Rule 4.
5. The maximum allowable cable length of a single
commnet segment is 12,000 feet. This may be