P341/EN O/B11 Operation Guide
CHAPTER 1 Introduction
Page 18/22 MiCOM P341
Note: *May vary according to relay type/model
Having made the physical connection to the relay, the relay’s communication settings
must be configured. To do this use the keypad and LCD user interface. In the relay
menu firstly check that the ‘Comms settings’ cell in the ‘Configuration’ column is set
to ‘Visible’, then move to the ‘Communications’ column. Only two settings apply to
the rear port using Courier, the relay’s address and the inactivity timer. Synchronous
communication is used at a fixed baud rate of 64kbits/s.
Move down the ‘Communications’ column from the column heading to the first cell
down which indicates the communication protocol:
Protocol
Courier
The next cell down the column controls the address of the relay:
Remote address
1
Since up to 32 relays can be connected to one K-bus spur, as indicated in Figure 7, it
is necessary for each relay to have a unique address so that messages from the
master control station are accepted by one relay only. Courier uses an integer
number between 0 and 254 for the relay address which is set with this cell. It is
important that no two relays have the same Courier address. The Courier address is
then used by the master station to communicate with the relay.
The next cell down controls the inactivity timer:
Inactivity time
10.00 mins
The inactivity timer controls how long the relay will wait without receiving any
messages on the rear port before it reverts to its default state, including revoking any
password access that was enabled. For the rear port this can be set between 1 and
30 minutes.
Note that protection and disturbance recorder settings that are modified using an on-
line editor such as PAS&T must be confirmed with a write to the ‘Save changes’ cell of
the ‘Configuration’ column. Off-line editors such as MiCOM S1 do not require this
action for the setting changes to take effect.
3.8.2 Modbus communication
Modbus is a master/slave communication protocol which can be used for network
control. In a similar fashion to Courier, the system works by the master device
initiating all actions and the slave devices, (the relays), responding to the master by
supplying the requested data or by taking the requested action. Modbus
communication is achieved via a twisted pair connection to the rear port and can be
used over a distance of 1000m with up to 32 slave devices.
To use the rear port with Modbus communication, the relay’s communication settings
must be configured. To do this use the keypad and LCD user interface. In the relay
menu firstly check that the ‘Comms settings’ cell in the ‘Configuration’ column is set
to ‘Visible’, then move to the ‘Communications’ column. Four settings apply to the
rear port using Modbus which are described below. Move down the
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