Siemens 7UT51 Instruction Manual page 169

7UT51 v3
3. Execute the function "4101 Measuring and
indication of current values".
4. Confirm your selection by clicking the Yes key.
The following screen will be displayed:
This displays all currents in percentage of 5A.
"Ix Ly" is an abbreviation for the Winding 'x'
Phase 'y' current. The "IA" (or "IB" if used)
current should read approximately 20.0%.
This metering test validates the current inputs to which
current is being applied.
Close up the test:
1. Close the "Test Results" window.
2. Close the "Commissioning Tests" window.
3. Display "4800 Commissioning Tests Stop."
4. Execute "4801 Stop the Commissioning Tests."
5. Confirm by pressing the Yes key.
6. Reset all targets and annunciations.
RGF Functional Test
The restricted ground-fault (RGF) protective function
must be parameterized as operative, On in
Address 1901.
To avoid misinterpretations, the trip signal of the 87
phase differential protection should be blocked. Yhis
can be done by setting the Address of 1601 to "Block
Tripping."
PRIM-2330C
RGF protection is based on detecting a zero sequence
source (such as a ground-fault or insulation degrading
to a ground-fault) in the zone defined by the location of
the phase CTs and the CT on the neutral of the
transformer. For instance, if a phase "a" to Gnd fault in
the winding happens on the wye side of a transformer,
current flows as shown in Figure 16.11. If the currents
in all the relay phase inputs were vectorially added to
the current at the ground input, the resultant would not
add up to 0. This situation indicates to the relay a
ground-fault is located between the phase CTs and the
ground CT.
.
A
B
C
Figure 16.11 Current Flow for Restricted Ground Fault
Inside of Protected Zone
16
Bench Testing
a
b
c
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