11-2
8 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
CHAPTER 11: MODBUS PROTOCOL
The following ModBus parameters are configurable:
Path:
Setpoints > Device > Communications > Modbus Protocol
MODBUS SLAVE ADDRESS
Range: 1 to 254 in steps of 1
Default: 254
For the RS485 ports each 8 Series relay must have a unique address from 1 to 254.
Address 0 is the broadcast address to which all Modbus slave devices listen. Addresses
do not have to be sequential, but no two devices can have the same address, otherwise
conflicts resulting in errors occur. Generally, each device added to the link uses the next
higher address starting at 1.
MODBUS TCP PORT NUMBER
Range: 1 to 65535 in steps of 1
Default: 502
The TCP port number used with Modbus over Ethernet. Note that the maximum number
of simultaneous Modbus connections supported over Ethernet is:
•
three for an 8 Series relay without the communications card,
•
five for an 8 Series relay with the communications card.
COMPATIBILITY
Range: Disabled, SR750
Default: Disabled
The Compatibility mode changes the Modbus actual value registers to emulate the
SR750. The emulation supports typical actual value data for common data items. See
the
8 Series Protective Relay Communications guide
for the list.
NOTE
NOTE:
When the device is programmed as a SR750, 850 actual values cannot be retrieved from
Modbus.
COMPATIBILITY
Range: Disabled, SR469
Default: Disabled
The Compatibility mode changes the Modbus actual value registers to emulate the
SR469. The emulation supports typical actual value data for common data items. See
the
8 Series Protective Relay Communications guide
for the list.
NOTE
NOTE:
When the device is programmed as a SR469, 869 actual values cannot be retrieved from
Modbus.
MODBUS ACTIVITY TIMEOUT
Range: 0 to 3600 s in steps of 1
Default: 0 s
The Modbus Activity Timeout specifies the minimum time without Modbus
communication. This timeout is used to declare the Modbus ‘Loss of Communication’
state.
The Modbus state is always Active if the Modbus Activity Timeout is 0 s.
MODBUS ERROR RESPONSES
The following exception response codes are implemented.