Areva MiCOM P441, Technical Manual

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P44x/EN IT/E33 Introduction
Page 20/24 MiCOM P441/P442 & P444
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 timer
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 ‘Communications’ column from the column heading to the first cell down which indicates
the communication protocol:
Protocol
Modbus
The next cell down controls the Modbus address of the relay:
Modbus address
23
Up to 32 relays can be connected to one Modbus spur, and therefore 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. Modbus uses an integer number between 1 and 247 for the
relay address. It is important that no two relays have the same Modbus address. The
Modbus address is then used by the master station to communicate with the relay.