GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 32)

Power Management Control System
Chapter 2 – Network Design
22
NOTE: Per the EIA485 standard, each RS-485
network supports up to 32 “drops” or electrical
drains on the network. However, the Ethernet
Gateway or RS-485 interface card counts as one
drop. Thus, only 31 other IEDs may be attached
to each RS-485 network, even though 32 Modbus
addresses are available for use. Also, unlike
commnet’s POWER LEADER Repeaters, RS-485
repeaters are counted as IEDs because although
they have no Modbus address, they do act as a
drop on the network.
Modbus
Address
Appropriate Usage/Supported IEDs
0 • Broadcast (not available to user)
1 – 32 • Modbus Concentrators must have addresses
in this range
• Other Modbus native IEDs may also have
addresses in this range
33 – 247 • Modbus native IEDs may have addresses in
this range
• Commnet IEDs must have addresses in this
range
Table 5. Modbus address range appropriate usage.
• Commnet IEDs are preprogrammed with a factory-set
address. You must change this address immediately
upon installation of the IED. Refer to the IED’s user
manual for instructions on assigning an address.
• Because the commnet network accepts a different
range of addresses than the Modbus network,
commnet addresses must be mapped to
corresponding Modbus addresses. The formula for
this mapping is: desired Modbus address + 267 = commnet
address to set at IED
. For example, to set a commnet
IED to Modbus address 33, the commnet address set
at the IED must be 300. Table 6 illustrates address
mapping.
For Modbus Address: Set commnet IED Address to:
33 300
34 301
35 302
... ...
246 513
247 514
Table 6. Modbus-to-commnet address mapping.
- You may want to block commnet address assignments
by lineup and/or Modbus Concentrator segment. For
example, start with 40 for the first lineup attached to
one Modbus Concentrator, 50 for the second lineup
attached, and so on. Addresses must be in the range
33 to 247. The example presented in Figure 18
demonstrates this.
- Increment the individual IEDs in each lineup by one.
For example, if the first IED in a lineup is Modbus
address 101, the second IED should be 102, the third
IED should be 103, etc.
• Addresses may be entered or changed at any time
that control power is present.
Figure 21 illustrates a sample network with IED addresses;
Table 7 provides details of the IEDs shown in Figure 21.