IG-150-EN version 04; 03/10/16
66
Protection functions. Description and settings General instructions
ekor.rps
4.6.5. Neutral directional (67N); polarization by S
0
+S-(V
0
+V
2
)
Operation with polarization by V
0
andV
2
The direction is determined regardless of the previous
criteria. If any of them determines that the direction is the
trip direction, the trip permission is given.
Trip permission without V
pol
(Directional Locking on the
display)
This setting is used only when in both of the previous
units the polarization magnitude is below the threshold
(Vpolarization setting).
Signaling
It provides forward and reverse signaling. The directional
units output is an OR of the polarization by voltage and
polarization by current units so that the trip permission
criterion prevails over the locking criterion.
Being the trip permission without V
pol
(directional locking)
set as “NO”, if the polarization magnitudes are below the
threshold the direction is not signaled.
Being the trip permission without V
pol
(Directional Locking)
set as “YES”, if the polarization magnitudes are below the
threshold signals reverse and forward.
4.6.6. Neutral directional (67N); polarization by I
Operation with polarization by current
The direction is determined comparing the earthing current
(I
pol
) with the neutral current. The trip direction happens
when both currents are in phase.
For the direction to be checked the following condition
must be fullled I
pol
>0.068A
There is a 5
th
zone between the locking zone and the trip
zone, for which the present directional status is maintained,
both if it is polarized by voltage or by current.
1
2
2
1
Trip zone
2
Locking zone
3
90 - Torque line
Figure 4.9. Zero sequence directional
Locking by lack of polarization
If the polarization current (I
pol
) falls below a threshold
(0.068A), it indicates that the fault is reverse and there is no
trip permission.
Signaling
It provides forward and reverse signaling.
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