Fronius Smart Meter 50kA-3, Руководство по эксплуатации

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Selection criteria
for current trans-
former General
Do not use current transformers with a voltage output.
Current transformers are directional. If they are mounted backwards or with reversed
wires, the measured power will be negative.
Primary current
Maximum current per phase. A current transformer is to be selected whose primary cur-
rent is higher than the maximum expected current per phase. The closer the expected
current is to this value, the more accurate the measurement.
Secondary current
The current transformer must supply 1 or 5 amps alternating current at nominal current.
The nominal data of the current transformer is stated in the current transformer data
sheet.
Power
The Fronius Smart Meter requires 0.3 VA to perform the measurement. In addition, there
are losses on the outgoing and return leads. The power of the current transformer must
be greater than the sum of the power of the Fronius Smart Meter and the leads. The
higher the power, the better.
Line resistances at different cross-sections (copper wires)
Secondary cur-
rent
[A]
Cross-section
[mm²]
Line resistances at different lead lengths
(outgoing and return lead)
0.5 m 1.0 m 2.5 m 5 m 10 m
5 1.5 0.3 VA 0.6 VA 1.5 VA 2.9 VA 5.8 VA
5 2.5 0.2 VA 0.4 VA 0.9 VA 1.8 VA 3.6 VA
5 4 - - 0.6 VA 1.1 VA 2.2 VA
Example
The length of the outgoing and return lead (0.5 m each) between the Fronius Smart
Meter and current transformer is 1 m in total and has a copper cable cross-section of 1.5
mm², so the line resistance is 0.6 VA according to the table above. The Fronius Smart
Meter's internal consumption is 0.3 VA.
Line resistance 0.6 VA + internal consumption 0.3 VA = 0.9 VA
→ A current transformer with an output of 1 VA, 1.5 VA, 5 VA or higher is suitable here.
Use accuracy class
1 or better (Cl. 0.5, Cl. 0.2, etc.). Class 1 corresponds to a deviation of ± 1% of the sec-
ondary current at maximum power.
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EN