6.Iec 60870-5-103 Bus - ABB REX 521 Technical Reference Manual, General

REX 521
4.1.12.6.
28
Protection Relay
Technical Reference Manual, General
IEC 60870-5-103 bus
The REX 521 includes an unbalanced IEC 60870-5-103 slave communication
interface.
The interface provides a fixed cross-coupling between the REX 521 application
(indications, commands and protection equipment) and the IEC 60870-5-103
protocol application data. The adjustable parameters are "Baud rate" and "Unit
address". User-selectable measurand sets "Frame type" are available for the
analogue measurement values.
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The physical bus topology is star-based. A star-coupler unit, e.g. RER 125, is needed
for connecting the REX 521 unit to a control system.The line idle state of the fibre-
optic interface is configurable ("light on" and "light off") with a parameter
"Tx mode".
For more information about the IEC 60870-5-103 bus, refer to Appendix on page 48.
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