[dw_7SR5_function87Tsettingsexample12, 1, en_US]
Figure 5-64
Dyn11 Transformer with Reverse Phase Notation
The 7SR24 relay is set to correspond to the vector group shown on the main transformer rating plate i.e. Dy11,
+30°. Relay instruments will indicate ’transformer’ quantities rather than system quantities.
Example n – Auto Transformer
Auto transformers have only 1 vector group for the auto-transformer winding Y(N)y0).
Neutral-point earthing affects all auto-transformer windings connected to the electrical power system. During
earth faults, coupling between both parts of the electrical power system occurs via the common earth-point.
For the connections below it is recommended that the CT ratios are matched to the rated currents of the wind-
ings and that Ydy0 vector correction settings are used. This is typical for auto-transformer with an unloaded
tertiary winding.
Protection and Automation Functions
5.22 87T Transformer Differential Protection
Reyrolle 7SR5, Transformer Protection Device, Device Manual 327
C53000-G7040-C015-1, Edition 11.2019
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