Siemens Argus 7SR21 Technical Manual page 391

• Receiver sensitivity. The light power at the receiver must be above the sensitivity of the
receiver in order that effective communication can occur.
• A 3dB safety margin is usually allowed after the budget calculation is performed.
Following installation and prior to putting into service the actual losses should be measured for each fibre using a
calibrated light source and meter. Measured and calculated values can be compared.
The following table can be used to record budget calculations:
A Launch power
B Fibre Type
C Loss (dB/km)
D Length
E Total fibre loss (CxD)
F No. of Splices
G Loss at each splice
H Total loss at splices (FxG)
I No. of connectors
J Loss per connector
K Total loss at connectors (IxJ)
L Total losses (E+H+K)
M Receive power budget (A-L)
N Safety Margin
O Device Receive Sensitivity
The following settings, on the COMMUNICATIONS MENU, must be configured when using the fibre Optic Com3
interface.
Setting Name
OFF
COM3 IEC60870-5-103
Protocol MODBUS-RTU
DNP3
COM3 0 - 254 for IEC60870-5-103
Station 1 - 247 for Modbus RTU
Address 0 - 65534 for DNP3.0
75 110 150 300
COM3 600 1200 2400 4800
Baud Rate 9600 19200 38400
57600 115200
NONE
COM3
ODD
Parity
EVEN
© 2017 Siemens Protection Devices Limited
Range/Options
Chapter 4 - Data Communications Definitions
Default Setting
IEC60870-5-103
0
19200
EVEN
dB
dB/km
km
dB
dB
dB
dB
dB
dB
dB
dB
dB
Notes
The protocol used
to communicate on
the standard RS485
connection.
An address within the
range of the relevant
protocol must be
given to identify the
relay. Each relay in a
network must have a
unique address.
The baud rate set
on all of the relays
connected to the
control system must
be the same as the
one set on the master
device.
The parity set on
all of the relays
connected to the
control system must
be the same and in
accordance with the
master device.
Chapter 4 - Page 11 of 96