Weidmüller PV DC COMBINER BOX, Operating Instructions Manual

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Connection of the communications (optional)
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6.5 Recommendations when configuring the
SCADA
If you will configurate the Scada or PLC acting as Modbus
client please follow these recommendations:
– The Modbus client timeout should be 1 second.
– The practical polling interval per slave should be 20 sec-
onds.
This is a good tradeoff between unnecessary network traf -
fic (and database size) and time resolution. Keep in mind
that the sun, the clouds and the MPP of the inverter do not
change significantly within 20 seconds!
– For the most efficient use of the PV site network band -
width the Modbus registers of each Transclinic should
be read in one single function code 0x04 "read input
registers", request spanning from registers 1 to 35. This
request will not create any 0x02 "illegal data address"
exception due to the "gaps" in the register table.
– The averaging window length should be 2.5 seconds.
– The system should prove the following measurement
and alarm information via Modbus:
– Averaged PV system voltage
– Averaged PV current for each input
– Averaged PCB temperature
– Status of the digital inputs
– Alarm flag: PV system under-voltage (user-configur -
able threshold)
– Alarm flag: Individual input undercurrent (user-config -
urable threshold)
– Alarm flag: Blown fuse
– Alarm flag: PCB over temperature (fixed threshold
70 °C)
– When connecting to SCADA please veify the electrical
drawings ensuring what string number is connected to what
Transclinic channel. String number one of the Combiner Box
may not be connected to channel number 1 of the Transclinic
and thereof. Map the SCADA and the Transclinic according to
the electrical drawings provided with the product in order to
obtain the correct current vaules displayed in the SCADA