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Technology:
every cable less makes life that little bit easier
The speed is therefore similar to that of an RS485
interface, i.e. between the typical applications for
smart metering (10 kbit/s) and network communi-
cation (>10 Mbit/s).
Limits and rules of thumb
The thresholds of this kind of system are based on
the cabling, loads and interferences on the power
lines. Several rules of thumb must be observed
when planning and installing the cabling. The signal
transmission quality largely depends on the signal
attenuation. This is caused by the line attenuation
and capacitive loads, such as input capacitors of
several nanofarads. Ideally, these are inductively iso-
lated in the respective loads. If this is not intended,
the level of interference can be reduced by adding
a short 10–40 cm stub cable to the main power line.
The S-Link interface is suitable for applications with
cable lengths of up to 100 m. The key factor in this
regard is not the cable length between two com-
municating components but the total cable length.
The maximum permissible cable length also reduc-
es depending on the number of components and
loads.
Test installation
The new photovoltaic system on the roof of the
Saia-Burgess Plant II in Murten was a good oppor-
tunity to use Saia® S-Link in a real life situation. In
addition to the solar panels, a weather station with
a webcam was also installed on the roof. A PCD1
reads the weather station data. As there is no 220
V or 24 V supply available on the roof, the compo-
nents were supplied by the switching cabinet on
the second floor. The PCD1 on the roof reads all the
weather data and transfers this together with the
webcam images via S-Link and the S-Bus protocol
to another PCD1 on the second floor. This acts as a
data concentrator and additionally collates the data
from different energy meters and the SMA invert-
ers. The SMA-own protocol is used for the latter. All
of this data is visualized on a Saia®Web panel in a
further switching cabinet.
The weather station can be directly accessed
via the internet:
or web code en1390a
Diagram of a real
Saia®S-Link application
for industrial use
Webcam
Temperature
Sunlight
Wind
Rain
Weather station
S-Link 24V
Solar-Panels
en1390
