Protection of an Auto Transformer
[dwsptran-170712-01.tif, 1, en_US]
Figure 6-279
Activation and Application Example of an Auto Transformer (500 MVA: 400 kV, 230 kV;
125 MVA: 34.5 kV)
Use the highest side rated current with the auto transformer for normalization. In the example (Figure 6-279),
the measuring point is M2 (230 kV side). For this side, a rated current of 500 MVA/(√(3) · 230 kV) = 1255 A
results. The primary transformer rated current is 1500 A. With this, you can estimate the minimum permissible
pickup value.
[foscwe01-170712-01.tif, 1, en_US]
Siemens recommends a setting value of 0.2 I/Irated,S.
•
Recommended setting value (_:103) Threshold = 0.2 I/Irated,S
Protection and Automation Functions
6.43 Restricted Ground-Fault Protection
874 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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