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 setting +/-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
Element Blocking
The undervoltage elements can be blocked by Binary Input Inhibit and VT Supervision. This func-
tionality should be checked.
Element BI Inhibits VT Supervision
27-1
27-2
27-3
27-4
Check correct indication, trip output, alarm contacts, waveform record.
When testing is complete reinstate any of the disabled functions.
Undervoltage Guard
If any 27 undervoltage element is set to be inhibited by the UV Guard element, this function should be
tested.
Connect the test voltage inputs to suit the installation wiring diagram utilizing any test socket facilities avail-
able. It may be useful to temporarily map an LED as General Pickup to assist during testing. UV Guard
operation will reset the General Pickup if no other element is operated. This LED should not be set as
Hand Reset in the output matrix.
Starting from nominal voltage, apply a step decrease to the applied voltage to a level below the 27 under-
voltage setting but above the 27UVG setting such that an undervoltage element operation occurs. Slowly
reduce the applied voltage until the 27 undervoltage element resets, this can be detected by the General
Pickup LED reset if no other element is operated (this includes any undervoltage element which is not UV
Guarded).
Phase
Setting (Volts) Tolerance V Element Used
for Test
Blocked Volts Notes
UVG
27Vx Undervoltage Protection – Vx
27Vx elements operate similarly to the 27 elements but are applied to the fourth voltage input Vx.
Where more than one 27Vx undervoltage 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
disabling the lower settings.
Note that if the voltage is reduced below the UV Guard setting threshold, the function may be blocked.
Current inputs are not required to stabilize the relay during voltage element testing.
9.9.3
Functional Tests
9.9 Protection Functional Tests
466 Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
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