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4.4. Function 67N. Inverse time directional neutral overcurrent
Two neutral directional units are available: 67N1 and 67N2.
This function uses the residual voltage as a polarization magnitude and the residual current as
an operating magnitude. The intervention sector in forward direction is defined in the following
way: the operating angle is rotated anticlockwise from the residual negative voltage -V0, which
gives us the maximum torque direction. A cone is drawn, with the half-cone angle adjusted, over
this maximum torque direction. In the same way, the intervention sector in reverse direction is
defined in the following way: the operating angle is rotated anticlockwise from the residual
positive voltage V0, which gives us the maximum torque direction. A cone is drawn, with the half-
cone angle adjusted, over the maximum torque direction.
If the directionality option is not activated, the 67N function behaves like a 50/51N/G function.
The actuation time starts when the following conditions are met simultaneously:
•
Residual voltage higher than adjusted
•
The phase shift of residual current and residual voltage is such that the residual current is
inside the intervention sector.
•
Residual current higher than adjusted
This protection function can be set by using these parameters
Group Description Minimum Maximum Step Unit Default
67N_1
67N_2
Inverse time directional neutral overcurrent
Permission - - Yes/No - No
Curve - - (1*) -
IEC Extrem.
Inverse
Time Dial (TMS) 0.02 2.20 0.01 - 1.25
Current Tap 0.10 7.00 0.01 I
nominal
0.50
Time delay 0.02 300.0 0.01 s 0.02
Directionality - - (2*) - No
Polarization voltage 2 65 0.1 V 40
Operating angle 0 359 1 ° (deg) 90
Halfcone angle 1 170 1 ° (deg) 90
(1*) IEC Inverse, IEC Very Inverse , IEC Extremely Inverse , IEC long time inverse, IEEEInverse, IEEEvery inverse,
IEEEextremely inverse, Defined time
(2*) No, Forward, Reverse
If the "definite-time" option is selected for the curve setting, the unit behaves as an instantaneous
directional overcurrent unit. In this case, the unit’s Time delay is adjusted using the "Time delay"
parameter.
If an inverse, very inverse or extremely inverse curve is selected in the curve setting, the Time
delay is a function of curve, dial and pickup adjustments.
If the unit operates with definite-time, the function starts up at 100% of the adjusted pickup and
resets at 95%.
If the unit operates with a curve, the function starts up at 110% of the adjusted pickup and resets
at 100%. Resets are instantaneous in both cases.