ABB 615 series Technical Manual page 479

1MAC059074-MB A
615 series ANSI
Technical Manual
of the power transformer is numerically matched on the high voltage and low voltage sides
by means of the Winding selection, 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.
Winding selection setting defines the protection relay location respect to the transformer.
If the protection relay is situated at the HV side of the transformer, then protection relay
location setting is set to "Winding 1" and respectively to "Winding 2" if protection relay
is situated at the LV side. If the differential protection relays are used to protect a line
without in-zone transformer, then the setting is set to "Not in use". In this case vector
group matching is ignored.
The matching of the phase difference is based on the phase shifting and the numerical delta
connection inside the protection relay. The Winding 1 type parameter determines the
connection on winding 1 ("Y", "YN", "D", "Z", "ZN"). The vector group matching can
be implemented either on both, winding 1 and winding 2, or only on winding 1 or winding
2, at intervals of 30° with the Clock number setting. Similarly, the Winding 2 type
parameter determines the connections of the phase windings on the low voltage side ("y",
"yn", "d", "z", "zn").
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 on one side turned 180° in
the protection relay.
Example 1, vector group matching of an 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
−
−
A B
I
=
AmHV
3
GUID-DB4A8A17-38B7-41B3-874B-B93776082C6E V1 EN
− −
I I
−
−
B C
I
=
BmHV
3
GUID-147F5433-7B16-4BC7-A502-90D5B0F00B06 V1 EN
− −
I I
−
−
C A
I
=
CmHV
3
GUID-11FB9BCE-F16E-4795-9AAD-FDCA4024241A V1 EN
Section 4
Protection functions
(Equation 70)
(Equation 71)
(Equation 72)
473