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D.4
Core Balance Current Transformer
General
The requirements for core balance current transformers are determined by the function "sensitive ground fault
detection".
The recommendations are given according to the standard IEC 60044-1.
Requirements
Maximum difference of the primary rated currents of the core balance current
transformer:
Select the primary rated current of the core balance current transformer so that
ground current flowing in the ground fault of the subnetwork is transmitted by
the core balance current transformer.
Transmission ratio, typical
Depending on the specific power system and the magnitude of the maximum
ground fault current, a different ratio may have to be selected.
Overcurrent limiting factor
Minimum power
Maximum connected burden
– for secondary current thresholds ≥ 20 mA
– for secondary current thresholds < 20 mA
Class Accuracy
Table D-2
Neutral point
Function directional
An angle correction may have to be parameterized at the device for particularly small ground fault currents
(see Description of the "Sensitive Ground Fault Detection").
SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
Minimum required class accuracy depending on the neutral point grounding and the operation
of the function
Isolated
Class 1
Current Transformer Requirements
D.4 Core Balance Current Transformer
Resonant-grounded system
Class 1
0.33 ≥ Ι
/ Ι
≤ 3
pn-lokal
pn-fern
60 / 1
FS = 10
1.2 VA
≤ 1.2 VA (≤ 1.2 Ω)
≤ 0.4 VA (≤ 0.4 Ω)
321
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