Siemens Reyrolle 7SR54 - 37 Undercurrent Protection - Phase

Element Blocking
The Vx Under Voltage elements can be blocked by Binary Input Inhibit. This functionality should be
checked.
Element BI Inhibits
27-1
27-2
Check correct indication, trip output, alarm contacts, waveform record.
When testing is complete reinstate any of the disabled functions.
Undervoltage Guard
If any Vx 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 27Vx under-
voltage setting but above the 27Vx UV Guard setting such that an undervoltage element operation occurs.
Slowly reduce the applied voltage until the 27Vx 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
Vx UVG
37 Undercurrent Protection – Phase
If 2 undercurrent 37 elements are used with different settings, it is convenient to test the element with the
lowest setting first. The higher setting element can then be tested without interference from the other
element.
Apply 3 phase balanced current at a level above the undercurrent 37-n setting until the element resets.
Reduce single phase current to below setting to prove the operation of the Pickup Option Any/All
setting.
If DTL setting is small, gradually reduce single phase current or 3 phase currents until element operates.
If DTL is large apply 1.1 times setting, check for no operation, apply 0.9 times setting, check operation.
Testing of this element phase by phase may cause inadvertent operation of the 46 NPS overcurrent elements.
Apply 0.5 times setting current and record operating time.
Phase
I
set
(Amps) DTL (sec) P.U. Current
Amps
Tolerence Op. Time 0.5 ⋅
I
set
Tolerance
CT1(I
A
)
CT2(I
B
)
CT3(I
C
)
Element Blocking
The undercurrent elements can be blocked by Binary Input Inhibit. This functionality should be
checked.
9.10.5
Functional Tests
9.10 Protection Functional Tests
Reyrolle 7SR5, Transformer Protection Device, Device Manual 425
C53000-G7040-C015-1, Edition 11.2019