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Modbus model
11.4.6
Modbus data and its corresponding structure are shown in the below. It illustrates IED (slave)
hardware and applications are monitored by the substation computer (master).
Application model
(i)
A practical model is shows in Figure 11.4-11. An IED is installed by a transmission line; The
substation computer is connected with the IED by the network. The line current and voltage
is monitored by the IED applications.
×
CT
Current signal
Voltage signal
VT
Modbus Data model
(ii)
Figure 11.4-12 shows that Modbus data model is laid with applications and hardware in the
IED. The applications are corresponded with Modbus functions using the GR-TIEMS. The
correspondences are achieved by mapping the IED signals (Data IDs) to the Modbus addresses.
Mapping between Applications (Data IDs) and Modbus (Addresses) by GR-TIMES engineering
IED
Applications
Voltage
Relays
Current
States
Binary
Measurements
input
Binary
Clock
output
IED hardware
IED applications
(BIO/ VCT)
IED
Relay application
OV function
UV function
FRQ function
Measurements
Figure 11.4-11 Image of Modbus applications
Signals
(Data IDs)
Addresses
4A10018300001B6F
4C20818F00001B76
4A10018300001B6F
4C20818F00001B76
7110812271001076
7110812378011098
303201330000E450
Modbus data model
Figure 11.4-12 Image of Modbus model
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Network
Ethernet /
Serial Link
Functions
01000
Discrete
Response
Inputs
09999
Read(0x01) / Write Request (0x05/0x15)
00000
Coils
Response
00999
10000
Input
Registers
Response
16999
Read (0x03)/Write Request (0x06,0x16)
17000
Holding
registers
23999
Response
Modbus query and response
6F2T0207 (0.01)
Substation
Computer
Read Request (0x02)
Read Request (0x04)
GRE200 (5,6)
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