V03522
For a forward direction, -VN hs to be in the shaded area
For a reverse direction, -VN has to be in unshaded area
IN
IN angle -RCA
Figure 113: Virtual Current Polarization
The Polarizing voltage (VNpol) is as per the table below and RCA is the relay characteristic angle defined by the
DEF Char. Angle setting.
Phase selector pickup VNpol
A Phase Fault VB + VC
B Phase Fault VA + VC
C Phase Fault VA + VB
No Selection VN = VA + VB + VC
5.3.2 NEGATIVE SEQUENCE POLARIZING
In certain applications, residual voltage polarization of Aided DEF may not be possible, or it may be problematic.
Example cases are:
● Where a 3-limb voltage transformer is fitted, which has no path for residual flux.
● Where the application features a parallel line and zero sequence mutual coupling may exist.
The problems in these applications can be alleviated using negative phase sequence (nps) voltage for polarization.
The nps voltage threshold must be set in the cell DEF V2pol Set.
Note:
The current quantity used for operation of the Aided DEF when it is nps Polarized is the residual current not the nps current.
The directional criteria with negative sequence polarization are as follows:
Directional forward
-90° < [(angle(V2) +180°) - (angle(I2) - RCA) ] < 90°
P543i/P545i Chapter 8 - Carrier Aided Schemes
P54x1i-TM-EN-1 229
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