ABB RELION REX640 Technical Manual page 685

1MRS759142 F
zero-sequence component on the star connected side that is earthed at its star
point has to be eliminated by using the
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
phase currents is calculated and reduced for each phase current:
I
L m 1
I
L m 2
I
L m 3
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 TPOSYLTC.
Typically, the tap changer is located within the high voltage winding, that is,
winding 1, of the power transformer. The
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" or "Winding 2".
The
voltage (and current). When the current tap position deviates from this value, the
input current values on the side where the tap changer resides are scaled to match
the currents on the other side.
A correct scaling is determined by the number of steps and the direction of the
deviation from the nominal tap and the percentage change in voltage resulting
from a deviation of one tap step. The percentage value is set using the
parameter.
The operating range of the tap changer is defined by the
Max winding tap parameters. The Min winding tap parameter tells the tap position
number resulting in the minimum effective number of winding turns on the side
of the transformer where the tap changer is connected. Correspondingly, the
REX640
Technical Manual
Zro A elimination parameter, the zero-sequence component of the
1
(
= I − x I + I + I
L 1 L 1 L 2
3
1
(
= I − x I + I +
L 2 L 1 L 2
3
1
(
= I − − x I + I +
L 3 L 1 L 2
3
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.
Tap nominal parameter tells the number of the tap, which results in the nominal
Zro A elimination parameter.
)
L 3
)
I
L 3
)
I
L 3
Tapped winding parameter specifies
Protection functions
(Equation 161)
Step of tap
Min winding tap and
Max
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