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90°. The θ of OCN can be set from -90° to 90°. The minimum voltage necessary to
maintain directionality can be set from 0.5 to 180 V.
Reverse
Operation zone
Directional characteristic
θ= 0°
angle line
Forward
Operation zone
θ= 0°
Figure 2.5-2
Characteristic of directional OCN in the reverse
(iii)
The reverse characteristic is a mirror image of the forward characteristic. The setting and the
scheme switch, in addition to providing the setting of the directional OCN element in the
forward direction, provides the setting of the directional EF element in the reverse direction:
for example, Reverse is set for the scheme switch [OCN1-Dir] when the direction of the OCN
element for stage 1 is considered.
Inverse time and definite time delay characteristic
2.5.2
The OCN element monitors the negative-sequence current; when the negative-sequence
current is beyond the threshold for the operation, the OCN element will operate within a period
that is defined by the time characteristic feature. The user can choose the one of the operate
time delay characteristics: (i) dependent (inverse) time characteristic delay (i.e., IDMT) or (ii)
independent (definite) time characteristic delay (i.e., DT). The operate time of the IDMT
depends upon the level of the negative-sequence current, whereas the operate time in the DT
is a constant.
For the reset time delay in the IDMT, either inverse (dependent)-time-reset or
definite(independent)-time-reset is characterized by the setting.
The user can select which characteristic will be applied to each stage of the OCN
Forward
Operation zone
Vpol
θ= +60°
Forward
Operation zone
θ= -60°
Examples of directional characteristic angle (θ)
- 92 -
Forward
Directional characteristic
Operation zone
angle line
θ= +60°
Vpol
Reverse
Operation zone
Reverse
Operation zone
Vpol
θ= -60°
Directional characteristic
Forward
angle line
Operation zone
6F2T0207 (0.01)
Directional characteristic
angle line
θ= +90°
Vpol
Reverse
Operation zone
θ= +90°
Reverse
Operation zone
Vpol
θ= -90°
Directional characteristic
angle line
θ= -90°
GRE200 (5,6)
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