Setting
(per Unit)
Setting
(volts)
Hysteresis
(%)
Calcu-
lated D.O.
(volts)
DTL
Setting
(sec)
P.U. Volts D.O. Volts Operate
Time
Notes
Check correct indication, trip output, alarm contacts, waveform record.
Inverse Time (24IT)
The inverse V/f element should be tested at each of the points specified by settings that constitute the overall
inverse characteristics.
Setting
(per Unit)
Setting
(volts)
Hysteresis
(%)
Calcu-
lated D.O.
(volts)
DTL
Setting
(sec)
P.U. Volts D.O. Volts Operate
Time
Notes
X0
Y0
Setting (per Unit)
Setting (volts)
DTL Setting (sec)
Operate Time
Notes
X1
Y1
X2
Y2
X3
Y3
X4
Y4
X5
Y5
X6
Y6
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
reset voltage to check the
Hysteresis
setting. If the DTL is long, the operate level should be checked by
applying a voltage of 90 % of setting voltage. Check hysteresis by resetting element to the operate level
setting plus the
Hysteresis
setting.
Connect the relevant output contact(s) to stop the test set. Step the applied voltage to a level below the
setting. The test set should be stopped at the operate time s/-5 %.
Test the other 2 phases by repeating the above if necessary.
When testing is complete reinstate any of the disabled functions.
Phase
Setting
(Volts)
DTL (sec) Hyst.
D.O.
(calcu-
lated)
P.U.
Volts
D.O Volts Op. Time
@ 0.5 ⋅
V
set
(UV)
UV
Guard
Toler-
ance
V
AB
/ V
A
V
BC
/ V
A
V
CA
/ V
C
9.10.3
Functional Tests
9.10 Protection Functional Tests
Reyrolle 7SR5, Transformer Protection Device, Device Manual
423
C53000-G7040-C015-1, Edition 11.2019