ABB RED615 Technical Manual page 394

Section 4
Protection functions
388
group matching is almost always made on the star connected side of the "Ynd" and
"Dyn" connected transformers.
If Clock number is "Clk Num 0" or "Clk Num 6", the zero-sequence component of
the phase currents is not eliminated automatically on either side. Therefore, the zero-
sequence component on the star connected side that is earthed at its star point has
to be eliminated by using the Zro A elimination parameter.
The same parameter has to be used to eliminate the zero-sequence component if
there is, for example, an earthing transformer on the delta-connected side of the
"Ynd" power transformer in the area to be protected. In this case, the vector group
matching is normally made on the side of the star connection. On the side of the
delta connection, the elimination of the zero-sequence component has to be
separately selected.
By using the Zro A elimination parameter, the zero-sequence component of the
phase currents is calculated and reduced for each phase current:
1
(
= − +
I I x I I
L m 1 L 1 L 1 L
3
1
(
I = I − x I + I
L m 2 L 2 L 1 L
3
1
(
I = I − − x I + I
L m 3 L 3 L 1 L
3
GUID-398EDAFF-4A32-4C39-AD75-1F6D19B8FF48 V1 EN
In many cases with the earthed neutral of a "wye" winding, it is
possible to make the compensation so that a zero-sequence
component of the phase currents is automatically eliminated. For
example, in a case of a "Ynd" transformer, the compensation is
made on the winding 1 side to automatically eliminate the zero-
sequence component of the phase currents on that side (and the "d"
side does not have them). In those cases, explicit elimination is not
needed.
Compensation of tap changer position
The position of the tap changer used for voltage control can be compensated and
the position information is provided for the protection function through the tap
position indication function TPOSSLTC1.
Typically, the tap changer is located within the high voltage winding, that is,
winding 1, of the power transformer. The Tapped winding parameter specifies
whether the tap changer is connected to the high voltage side winding or the low
voltage side winding. This parameter is also used to enable and disable the
automatic adaptation to the tap changer position. The possible values are "Not in
use", "Winding 1", "Winding 2".
)
+
I
2 L 3
)
+ I
2 L 3
)
+ I
2 L 3
1YHT530004D05 D
(Equation 48)
615 series
Technical Manual