∅ a ≥ 2 x ∅ b
Transformer connection
Transformer connecting cables must be twisted and not routed in parallel to live cables to protect
from emitted interference. Keep the length of the connecting cables to a minimum. The
resistance at the transformer connecting cable must not exceed 5 Ω to ensure correct fault
current monitoring. This is ensured by the following limits given here as examples.
Conductor cross-section [mm²] AWG/[kcmil] Max. cable length [m]
0.5 20 70
1.0 18 140
1.5 16 210
2.5 14 / 12 300
4.0
1)
10 550
1)
only possible in the case of transformers with a 210 mm diameter
Note
We recommend using twisted cables.
① Maximum cable lengths (see table above) ① Length ≥ 10 m (shielded, twisted, grounded cables)
Accessories
13.2 Accessories for 3UG4 monitoring relays
SIRIUS 3UG4 / 3RR2 monitoring relay
Equipment Manual, 07/2021, NEB927043002000/RS-AD/005 253
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