Protective Elements
Connection Groups
»W1 Connection/Grounding«
Allowed Settings: Y, D, Z, YN, ZN
This is the setting for the connection scheme of the winding W1 of the transformer and its grounding condition.
»W2 Connection/Grounding«
Allowed Settings: y, d, z, yn, zn
This is the setting for the connection scheme of the winding W2 of the transformer and its grounding condition.
The combination of »W1 Connection/Grounding« and »W2 Connection/Grounding« allows for all possible physical
connection schemes of transformers. The N or n can be set whenever the neutral of the transformer is connected to
ground and the grid on that side of the winding is grounded.
»Phase Shift«
Allowed Settings: 0, …, 11
The phase shift is set in multiples of 30° and defines the angle by which the voltage on the W2 side lags the
voltage on the W1 side.
Phase shift in multiples of 0...11 * (-30) degree that the secondary voltage lags the primary voltage.
Please refer to the Phase Compensation section for a number of typical, preferred transformer types.
For (Y, y, Z, z) connections, the neutral can be connected to ground or not connected to ground. In general, there is
a distinction between odd (1, 3, 5, …, 11) and even (0, 2, 4, …,10) connection numbers. Together with the
connection scheme (y, d, or z) and the treatment of the neutral of the transformer, the following definitions are
taken.
• The three-phase symmetrical system I1 is rotated counter-clockwise when transferring from winding 1 to
winding 2 (applies for ABC phase sequence).
• The three-phase symmetrical system I2 is rotated clockwise when transferring from winding 1 to winding 2.
(applies for ABC phase sequence).
• The connection of the transformer to a negative rotating system (ACB) is taken into account according to the
parameter.
• The transformation of the zero sequence system I0 depends on the connection of the windings:
– Only (Y, y, Z, z) – connections provide for an external available neutral point;
– Only when this neutral point is connected to ground (this is indicated by an appended “n” in the winding
group setting (example Dyn)), and at least another ground connection is available
on the grid to which the winding is connected (a zero sequence - respectively ground current can flow);
and
– Only when both windings of the transformer allow for ground current flowing, the zero sequence current
can be transformed from one side of the transformer to the other without any phase shift.
• Odd connection groups are created by Dy, Yd, Yz, Zy schemes.
• Even connection groups are created by Yy, Zd, Dz, Dd.
• The primary values of winding 1 are reference values when displaying or evaluating relative values.
The transformer ratio can be modified by a tap changer.
642 MCDGV4 DOK-HB-MCDGV4-2E
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