FUNCTION CHARACTERISTICS
30
NA30 - Manual - 04 - 2022
4.3 I/O DESCRIPTION
Metering inputs
The following input are provided:
• Three phase current inputs.
• One residual current input.
• The nominal currents are independently adjustable at 1 A or 5 A through DIP-switches.
• One residual voltage input, with programmable nominal voltage within range 50...130 V (U
ER
=100 V).
The input circuits are appropriately dimensioned in order to withstand the currents which arise
when a fault occurs, both in transient and steady state condition.
Signal processing
Various processing levels are involved:
• Acquisition (base level).
• Direct measures of physical channels (first level).
• Calculated measures (second level).
• Derived (third level).
The measures concerning a level are based on data worked out in the previous level.
For each level the required resources concerning the priority for tasks (conditioning circuits, DSP
and CPU) are on hand.
ACQUISITION (base level)
The input signals are sampled 24 times per period:
- i
L1
...i
L3
Phase current instantaneous values
- i
E
Residual current instantaneous value
- u
E
Residual voltage instantaneous value
From the sampled quantities, several measures are computed for protection, monitoring and meter-
ing purposes.
sensori.ai
NA30
3 ingressi correnti di fase
1 ingresso di corrente residua
1 ingresso di tensione residua
acquisizione.ai
ACQUISITION
INSTANTANEOUS MEASURES
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