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.
Parameter: 67GS > 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 > Compensated Network
•
Default setting: Disabled
For resonant grounded systems where compensation (Petersen) coils are fitted, earth fault current is
deliberately reduced to zero and therefore is difficult to measure for protection purposes. However, the
wattmetric component in the capacitive charging currents, which are close to the directional zone boun-
dary, can be used to indicate fault location. It is advantageous to increase the directional limits towards ±
90° so that the directional boundary can be used to discriminate between faulted and healthy circuits.
This feature must be enabled for use with compensated networks only.
Parameter: 67GS > Wattmetric
•
Default setting: Disabled
This setting is used to allow the element to be switched on and off if it is not required. A separate setting
is provided for each element.
Parameter: 67GS > Wattmetric Power
•
Default setting: 0.10 x I
n
x W (0.10 ⋅ I
rated
⋅ W)
Parameter: 67GS > Ires Select
•
Default setting: Ires
Use of only the sine (reactive) component of the residual current is achieved by setting Ires Select to
Ires Real.
Where it is required to select the operating current to I
RES
Cos(θ - ∅) the characteristic angle is set to ∅ to
+90°.
See Figure 5-47.
Parameter: 67N > Polarizing Quantity
•
Default setting: ZPS
The 67N directional element provides forward and reverse outputs that can be used to control each
calculated earth fault element. The directional calculated earth fault elements use zero or negative phase
sequence polarizing.
Polarizing Quantity
I (Operate) V (Reference)
ZPS I
0
V
0
NPS I
2
V
2
Protection and Automation Functions
5.25 67 Directional Overcurrent/Earth Fault
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 329
C53000-G7040-C014-1, Edition 11.2019
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