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This can be repeated for the reverse load settings for clarity if required. Increasing the 3 phase current angle in
the leading (positive) direction from forwards towards anti-phase (180 degrees) with respect to the 3 phase
voltage will pick up the Load Blinder REV signal when the angle from 180° equals the Angle +ve setting.
Increasing still further in the anticlockwise direction will approach the Reverse(-) boundary. The Load
Blinder REV signal will reset when the angle is above the Angle -ve setting plus 180° plus 3° hysteresis and
will pickup again when the angle is reduced to below 180° plus Angle -ve angle setting.
Table 9-1
Load Blinder region
Angle
V
Setting
1
V
Setting can be checked by reducing balanced 3 phase voltage to below the setting with the low level
1
current as above, applied at zero degrees.
Table 9-2
Parameters
V
Setting
1
Determining Impedance Sensitivity
The impedance can be calculated directly from phase-neutral voltage divided by phase current.
Apply balanced 3 phase rated voltage and balanced 3 phase rated current. Calculate the current required to
achieve the relay impedance setting with nominal voltage. If this is possible without exceeding relay thermal
rating it can be injected manually. Increase the current until the Load Blinder FWD resets. If the current
required will exceed the continuous rating, short duration tests will be required at 90 % of impedance setting.
Alternatively, voltage can be reduced to allow lower current to be applied to achieve the required impedance
but the V
Setting must always be exceeded as this will otherwise block the operation.
1
Table 9-3
Parameters
Impedance Ω
Voltage V
9.9.2
27 Undervoltage Protection – 3 Phase
Where more than 1 undervoltage (27) elements are being used with different settings, it is convenient to test
the elements with the lowest settings first. The elements with higher settings can then be tested without disa-
bling the lower settings.
Note that if the voltage is reduced below the 27UVG setting, the function may be blocked. VTS operation may
also block the 27 undervoltage function. Current inputs are not required to stabilize the relay during voltage
element testing.
The 27 undervoltage can be set to operate from phase to phase or phase to neutral voltage. Test voltage
should be connected to suit.
If the Pickup Option is set to All, the voltage on all phases must be reduced simultaneously. Otherwise
the 3 phases should be tested individually. Balanced nominal rated voltage should be connected to the 3
phases. If the DTL is short, starting from nominal voltage, slowly decrease the applied 3P or appropriate single
phase test voltage until the Pickup LED (temporarily mapped) is on. Record the operate voltage. The LED
should light at setting Volts +/-5 %. Slowly increase the input voltage until the LED extinguishes. Record the
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
Angle boundary
Forward (+) Boundary
Angle = (Default=20°)
PU (Raised)
V
Setting
1
Setting
42 V
Trip Level
Setting
63.5
DO (Reset)
PU (Raised)
Operation
DO
Functional Tests
9.9 Protection Functional Tests
Forward (-) Boundary
Angle = (Default=20°)
DO (Reset)
PU
465
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