ABB RELION 620 Series Technical Manual page 432

Section 4
Protection functions
426
relay from the corresponding windings does not change. When the phase shift setting
between windings is 180.0 degrees, the phase currents from the other winding turns 180°
in the protection relay.
The transform is first applied to the set of 3 line currents on the winding 1 side of the power
transformer, and then on the set of 3 line currents on the winding 2 side. In this case, the
power transformer winding 1 side is taken as a reference with zero phase shift, while the
winding 2 side has a phase shift Θ.
The Phase Ref winding setting can be used to give the possibility 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 regarding the possible removal of zero-sequence
current if needed) when the currents in other windings are matched with the reference
winding (if the set phase shift between the windings is not zero).
Zero-sequence component elimination
If the zero-sequence component is to be removed on one, two or all sides of the
transformer, the Zro A elimination setting can be used. In case one or more windings is
delta-connected and there is no separate neutral grounding transformer on that winding,
zero-sequence component removal is not recommended to be selected. There is no path
for the zero-sequence current to flow in such a winding.
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 for the protection
function through the tap position indication function 84T.
Typically, the tap changer is located within the HV winding, that is, winding 1 of the
power transformer. The Tapped winding setting parameter specifies whether the tap
changer is connected to winding 1, winding 2 or winding 3. The Tapped winding setting
parameter is also used to enable or disable the automatic adaptation to the tap changer
position. The possible values are "Not in use" (1), "Winding 1"(2), "Winding 2" (3),
"Winding 3" (4).
There can be only one tap changer in the transformer, that is, the function
can take into account and compensate only for one tap changer.
The Tap nominal setting parameter provides the number of the tap which results in the
nominal voltage and current. When the current tap position deviates from this value, the
input current values where the tap changer resides are scaled to match the currents on the
other side.
1MAC504801-IB E
620 series ANSI
Technical Manual