ABB RELION REX640 Technical Manual page 873

1MRS759142 C
REX640
Technical Manual
The polarizing quantity is -U
of zero-sequence voltage polarization.
The polarizing quantity is -U
of negative-sequence polarization.
In case of zero-sequence current polarization "Zero seq. cur.", the zero-sequence
current I of the protected line is the operating quantity while another reference zero-
0
sequence current I is the polarizing quantity. I
0ref
from the neutral of a power transformer. In case of zero-sequence current polarization,
the relay characteristic angle Chr angle GFC is internally fixed and is equal to zero
degrees. The zero-sequence current direction must remain unchanged during all
network configurations and faults. Therefore, all transformer configurations or
constructions are not suitable for polarization.
In case of dual polarization "Zro vol. OR cur.", the zero-sequence voltage polarization
and zero-sequence current polarization elements are logically OR:ed. Typically,
when I is high, U is low, and when I
0 0
benefit from both elements as the two polarization methods complement each other.
If the zero-sequence current polarization source is switched off for service, the
flexibility is increased as the zero-sequence voltage polarization can be used.
Faulted loop phase selection
A reliable identification of a fault and faulted phases is needed to guarantee a selective
operation of the distance protection. This information is used to release correct
measuring elements of the protection zones.
In DSTPDIS, the faulted phase selection can be done in various ways and defined with
the Phase Sel mode GFC setting.
Table 830: Supported methods for phase selection
Setting
Phase Sel mode GFC
The "Overcurrent" method is the basic method for identifying the faulted phases. It
can be used in applications where the fault current magnitude exceeds the load current
despite the changes in the network configuration and fault type.
The "Vol Dep Overcur" method combines overcurrent and undervoltage conditions.
An undervoltage condition allows lower current threshold settings and increases the
sensitivity of the fault detection.
The "Under impedance" method uses fault loop impedance for identifying the faulted
phases. The underimpedance characteristic can be either quadrilateral or circular in
shape. The sensitivity of the fault detection is defined by an independent setting in
Protection functions
and the operating quantity is I
0
and the operating quantity is I
2
, for example, could be the current
0ref
is low, U is high. Hence the protection can
0 0
Enumerator value
• Overcurrent
• Vol Dep Overcur
• Under impedance
• OC AND Und impedance
Section 4
in case
0
in case
2
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