The characteristic angle is the phase angle by which the reference voltage must be adjusted such that the
directional detector gives maximum sensitivity in the forward operate zone i.e. when the operate current is in
phase with the polarizing voltage. A fault is determined to be in the selected direction if lies within +/- 85° of
the Characteristic Angle setting.
For fault current of -15° (I lagging V by 15°) a setting of -15° is required for maximum sensitivity OR
For fault current of -45° (I lagging V by 45°) a setting of -45° is required for maximum sensitivity.
The reverse operate zone is the mirror image of the forward zone.
[dw_7SR5_function67ApplicationAndSettingNotes2, 1, en_US]
Figure 5-39
Earth Fault Directional Characteristic
Parameter: 67G > Minimum Voltage
•
Default setting: 0.33 V
This setting defines the minimum polarizing voltage level. Where the measured voltage is below this level
no directional output is given and protection elements set as directional will not operate. This prevents
mal-operation under fuse failure/MCB tripped conditions where noise voltages can be present.
Parameter: 67GS > Char Angle
•
Default setting: -15°
The 67GS directional element provides forward and reverse outputs that can be used to control each
sensitive earth fault element.
The sensitive directional earth fault elements use the zero phase sequence (V
0
) voltage as the reference
quantity and the zero phase sequence current (I
0
) phasor is the operate quantity.
I (Operate)
V (Reference)
I
0
V
0
Protection and Automation Functions
5.25 67 Directional Overcurrent/Earth Fault
328 Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
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