ABB Relion 670 series - Page 287

- 3V
0
3I
0
AngleRCA
AngleOp
en06000417_ansi.vsd
ANSI06000417 V1 EN
Figure 143: Principle for zero-sequence voltage polarized additional directional
element
Negative-sequence voltage polarization is utilizing the phase relation between the
negative-sequence voltage and the negative-sequence current at the location of the
protection.
Zero-sequence current polarization is utilizing the phase relation between the zero-
sequence current at the location of the protection and some reference zero-sequence
current, for example, the current in the neutral of a power transformer.
The principle of zero-sequence voltage polarization with zero-sequence current
compensation is described in figure
144. The same also applies for the negative-
sequence function.
Z0
SA
Z0
SB
Z0
Line
V0
I0
IF
I0
V0
K*I0
V0 + K*I0
Characteristic
angle
en06000418_ansi.vsd
ANSI06000418 V1 EN
Figure 144: Principle for zero sequence compensation
Note that the sequence based additional directional element cannot give per phase
information about direction to fault. This is why it is an AND-function with the normal
1MRK505222-UUS C Section 6
Impedance protection
281
Technical reference manual