P44x/EN SC/Hb
P442, P444 (SC) 12-
It is possible to use the products field voltage output (48 V DC) to bias the bus using values
of 2.2 kΩ (½W) as bias resistors instead of the 180 Ω resistors shown in the above diagram.
The following warnings apply:
• It is extremely important that the 120 Ω termination resistors are fitted. Failure to do so
will result in an excessive bias voltage that may damage the devices connected to the
bus.
• As the field voltage is much higher than that required, Alstom Grid cannot assume
responsibility for any damage that may occur to a device connected to the network as
a result of incorrect application of this voltage.
• Ensure that the field voltage is not being used for other purposes (i.e. powering logic
inputs) as this may cause noise to be passed to the communication network.
1.2.2 Courier communication
Courier works on a master/slave basis where the slave units contain information in the form
of a database, and respond with information from the database when it is requested by a
master unit.
The relay is a slave unit that is designed to be used with a Courier master unit such as
MiCOM S1 Agile, MiCOM S1,PAS&T or a SCADA system.
To use the K-Bus rear port to communicate with a PC-based master station using Courier, a
KITZ K-Bus to EIA(RS)232 protocol converter is required. This unit is available from General
Electric. A typical connection arrangement is shown in Figure 2. For more detailed
information on other possible connection arrangements refer to the manual for the Courier
master station software and the manual for the KITZ protocol converter. Each spur of the K-
Bus twisted pair wiring can be up to 1000m in length and have up to 32 relays connected to
it.
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