GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 49)

Power Management Control System
Chapter 3 – Network Wiring and Construction
39
Type of Wire
Ethernet
10Base-T applications may use any appropriate Category 3,
4 or 5 UTP cable, provided it is rated at least 300V.
Category 3 cable is sufficient for 10 Mbps applications such
as PMCS. Category 5 cable supports 100 Mbps network
applications. Category 4 cable is not widely available,
having been superseded by Category 5 cable in the
marketplace. Any of these cables may be used in 600 volt
applications by applying 600V tubing to the cable.
Modbus
Belden 9841 or Alpha 6412 may be used for applications
under 300 V that are indoors or outdoors in conduit above
grade. These cables may be also be used for 600 V
requirements by applying 600 V tubing to them. Belden
3074F may be used for applications greater than 300 V
which are indoors or outdoors in conduit above grade.
Commnet
Belden M8719 shielded instrumentation cable #16 AWG
wire (shielded, twisted-pair) is recommended for
commnet wiring for applications indoors or outdoors in
conduit above grade.
For below-grade applications, Belden 83702 shielded 16
AWG cable is recommended. Belden 83702 is rated for direct
burial and air plenum, nonconduit applications, but the length
limits for this cable are two-thirds of the lengths specified in the
configuration rules of Section 2-1.
For example, a network
segment connecting up to four IEDs may have a total cable
length of no more than 667 feet of Belden 83702, versus
the 1000-foot limit on total cable length for Belden 8719.
Termination
RS-485 cables must be terminated at each end of the
network with a 120-ohm,
1/2 -watt, 5% tolerance resistor.
IMPORTANT NOTE FOR CONNECT TECH
CARD USERS:
The Connect Tech RS-485 card
recommended for use with PMCS systems
requires a 600-ohm rather than a 120-ohm
resistor. Use the 600-ohm resistor at the Connect
Tech card only. The other end of the Modbus
network(s) should be terminated with the usual
120-ohm resistor.
IMPORTANT NOTE FOR ETHERNET
GATEWAY USERS:
The POWER LEADER
Ethernet Gateway provides internal termination
for its four RS-485 ports. No terminating resistor
is needed at the POWER LEADER Ethernet
Gateway.
See Figure 9 for an example of the cable run terminated at
the final IED on the network.
Shield Grounding
Modbus
The RS-485 cable shield must be grounded at only a single
point on each RS-485 wire. Connect the shield to the
ground terminal at the Ethernet Gateway or RS-485
interface card. Connect the cable shield to the shield
terminal at each IED on the RS-485 network except the
Multilin 565, which does not have isolated communication
ports (Modbus Rule 5, Section 2–4).
Commnet
The commnet cable shield must be grounded at only a
single point in each commnet segment. This is done at the
POWER LEADER Modbus Concentrator. Each commnet
port on the Modbus Concentrator has a ground terminal,
and each commnet segment should be grounded at the
port to which it is connected.
Figure 28 shows a POWER LEADER Modbus Concentrator
connected to a series of commnet IEDs. The shield of the
cable to the downstream IEDs is grounded at the Modbus
Concentrator on its internal shield-ground terminal strip.
3–2 Modbus – Commnet Integration
The rules regarding the number of IEDs per Modbus
Concentrator and wiring-distance limits are explained in
Chapter 2. The rules expressed in this section are more
low-level and concern the physical connections of
commnet IEDs to a Modbus Concentrator. You must follow
these rules to provide for proper shielding and
communications.
Wiring Concerns
No commnet segment should have more than one wiring
connection at any point, such as the Modbus
Concentrator, a Junction Box, or a Repeater. You must
avoid this condition, which is known as looping.
Examples of correct wiring conditions and various illegal
looping conditions are illustrated in Figure 28 through
Figure 32. Figure 28 illustrates correct commnet wiring.
Figure 29 through Figure 32 show illegal looped wiring.
You can correct looping by removing either of the looped
connections indicated by the large Xs in the figure.