When the vector group matching is Yy0 and the
CT connection type is according to
"Type 2", the phase angle of the phase currents connected to the protection relay
does not change. When the vector group matching is Yy6, the phase currents are
turned 180° in the protection relay.
Example 1
Vector group matching of a Ynd11-connected power transformer on winding
1,
CT connection type according to type 1. The Winding 1 type setting
is ”YN”,
Winding 2 type is “d” and Clock number is “Clk Num 11”. This is
compensated internally by giving winding 1 internal compensation value
+30° and winding 2 internal compensation value 0°:
I
I
I
I
I
I
I
I
I
L mHV
L
L
L mHV
L
L
L mHV
L
L
1
1
2
2
2
3
3
3
1
3
3
3
=
−
=
−
=
−
(Equation 71)
Example 2
But if vector group is Yd11 and
CT connection type is according to type
1, the compensation is a little different. The
Winding 1 type setting is ”Y”,
Winding 2 type is “d” and Clock number is “Clk Num 11”. This is compensated
internally by giving winding 1 internal compensation value 0° and winding 2
internal compensation value -30°;
I
I
I
I
I
I
I
I
I
L mLV
L
L
L mLV
L
L
L mLV
L
L
1
1
3
2
2
1
3
3
2
3
3
3
=
−
=
−
=
−
(Equation 72)
The "Y" side currents stay untouched, while the "d" side currents are
compensated to match the currents actually flowing in the windings.
In this example there is no neutral current on either side of the transformer
(assuming there are no earthing transformers installed). In the previous
example, however, the matching is done differently to have the winding 1
neutral current compensated at the same time.
Zero-sequence component elimination
If
Clock number is "Clk Num 2", "Clk Num 4", "Clk Num 8" or "Clk Num 10", the vector
group matching is always done on both, winding 1 and winding 2. The combination
results in the correct compensation. In this case the zero-sequence component is
Protection functions
1MRS757644 H
522
620 series
Technical Manual
