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Vector group matching and elimination of the zero-sequence component
The vector group of the power transformer is numerically matched on the high voltage and
low voltage sides by means of the
Winding 1 type
,
Winding 2 type
and
Clock number
settings. Thus no interposing CTs are needed if there is only a power transformer inside
the protected zone. The matching is based on phase shifting and a numerical delta
connection in the protection relay. If the neutral of a star-connected power transformer is
grounded, any ground fault in the network is perceived by the protection relay as a
differential current. The elimination of the zero-sequence component can be selected for
that winding by setting the
Zro A elimination
parameter.
Table 432:
87T settings corresponding to the power transformer vector groups and zero-sequence
elimination
Vector group of the
transformer
Winding 1 type
Winding 2 type
Clock number
Zro A Elimination
Yy0
Y
y
Clk Num 0
Not needed
YNy0
YN
y
Clk Num 0
HV side
YNyn0
YN
yn
Clk Num 0
HV & LV side
Yyn0
Y
yn
Clk Num 0
LV side
Yy2
Y
y
Clk Num 2
Not needed
YNy2
YN
y
Clk Num 2
Not needed
YNyn2
YN
yn
Clk Num 2
Not needed
Yyn2
Y
yn
Clk Num 2
Not needed
Yy4
Y
y
Clk Num 4
Not needed
YNy4
YN
y
Clk Num 4
Not needed
YNyn4
YN
yn
Clk Num 4
Not needed
Yyn4
Y
yn
Clk Num 4
Not needed
Yy6
Y
y
Clk Num 6
Not needed
YNy6
YN
y
Clk Num 6
HV side
YNyn6
YN
yn
Clk Num 6
HV & LV side
Yyn6
Y
yn
Clk Num 6
LV side
Yy8
Y
y
Clk Num 8
Not needed
YNy8
YN
y
Clk Num 8
Not needed
YNyn8
YN
yn
Clk Num 8
Not needed
Yyn8
Y
yn
Clk Num 8
Not needed
Yy10
Y
y
Clk Num 10
Not needed
YNy10
YN
y
Clk Num 10
Not needed
YNyn10
YN
yn
Clk Num 10
Not needed
Yyn10
Y
yn
Clk Num 10
Not needed
Yd1
Y
d
Clk Num 1
Not needed
Table continues on next page
Section 4
1MAC059074-MB A
Protection functions
520
615 series ANSI
Technical Manual
Содержание Relion 615 series
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