ABB RELION REX640 - Page 720

Phase difference matching is based on the ABB-patented generalized transform
method. Settings Phase shift Wnd 1-2 and Phase shift Wnd 1-3 determine the current
phase angle difference between windings 1 and 2 and between 1 and 3, respectively.
Normally, the transformer vector group designation includes the winding
configurations and the phase angle difference between given with a clock number.
For example, YNd1 has clock number 1. Settings Phase shift Wnd 1-2 and Phase shift
Wnd 1-3 are calculated as clock number · 30 deg.
Table 665: Examples of Phase shift Wnd 1-2 (and Phase shift Wnd 1-3) settings for
some common vector groups
Vector group between windings 1 and 2 (or windings 1 and
3)
Phase angle
YNd1, Yd1, Dyn1, Dy1 30°
YNd5, Yd5, Dyn5, Dy5 150°
YNd7, Yd7, Dyn7, Dy7 210°
YNd11, Yd11, Dyn11, Dy11 330°
The vector group matching can be set in the resolution of 0.1 degrees, which allows
for cycloconverter applications with a phase angle difference of, for example, 7.5
degrees between windings.
The Phase Ref winding setting is used to define which of the windings is the
reference. The phase reference can be selected from Phase Ref winding as "Winding
1", "Winding 2" or "Winding 3". The currents in the winding selected as the phase
reference are not modified (except the removal of the zero-sequence current if set
active) when the currents in other windings are matched with the reference winding
(if the set phase shift between the windings is not zero).
The
Phase Ref winding setting does not affect settings Phase shift Wnd
1-2 and Phase shift Wnd 1-3 .
Zero-sequence component elimination
If a wye-connected power transformer neutral is earthed, or if there is a separate
earthing transformer inside the differential protection zone, any out-of-zone earth
fault in the network is seen as differential current unless the zero-sequence
component is correctly eliminated.
The zero-sequence elimination is done with the Zro A elimination setting. The
recommended rules for this setting are:
• For power transformer wye-connected windings with earthed neutral point, Zro
A elimination must be activated.
• For power transformer wye-connected windings with isolated neutral, and for
delta-connected windings, Zro A elimination is not activated unless there is a
separate earthing transformer inside the protected zone (that is, between the
power transformer winding and CTs).
• It does no harm to activate Zro A elimination even if it is not needed.
Compensation of tap changer position
The position of the tap changer used for voltage control can be compensated
according to the actual tap changer position. The position information is provided
Protection functions
1MRS759142 F
720 REX640
Technical Manual