Siemens 7SR18 Solkor - Inverse Time Overcurrent (51 C); ANSI Reset

7SR18 Commissioning & Maintenance Guide
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3.4.1 INVERSE TIME OVERCURRENT (51C)
It will be advantageous to map the function being tested to temporarily drive the relevant Pickup output in the
Pickup Config sub-menu in the Output Config menu as this will allow the Pick-up led to operate for the function.
Gradually increase current until Pickup LED operates.
Apply 2x setting current and record operating time,
Apply 5x setting current and record operating time.
Compare to calculated values for operating times
P.U.
D.O.
&
TIMING
TESTS
Ph.
Dir
Char.
(NI EI VI LTI,
DTL)
Is
(A)
TM
Operate Current
Operate Time
P.U.
(A)
D.O.
(A)
Tol
2 x Is
(s)
5 x Is
(s)
Tol
I
L1
(I
A
)
I
L2
(I
B
)
I
L3
(I
C
)
Calculated Timing values in seconds for TM =1.0
Curve 2 xIs 5 xIs
IEC-NI 10.03 4.28
IEC-VI 13.50 3.38
IEC-EI 26.67 3.33
IEC-LTI 120.00 30.00
ANSI-MI 3.80 1.69
ANSI-VI 7.03 1.31
ANSI-EI 9.52 1.30
Note that the operate time may be subject to the Minimum op time setting for the element and/or may have a
Follower DTL applied.
3.4.2 ANSI RESET
If the element is configured as an ANSI characteristic, it may have a reset delay applied. If ANSI reset is selected
for an IEC characteristic element, the reset will be instantaneous.
ANSI reset times from operated condition to fully reset are as follows for zero applied current and TM = 1.0. The
reset curve characteristic type and TM is defined by the operating characteristic.
Curve Fully operated to reset with Zero current applied & TM=1 (seconds)
ANSI-MI 4.85
ANSI-VI 21.6
ANSI-EI 29.1
Apply current in the following sequence, a) 2x setting for a time to ensure element operation, b) Zero current for
the reset time above (xTM), c) 2x setting for a time to ensure element operation. Check that the second operation
(c) is similar to the first (a) and in line with the expected operate time for the element at this current level.
Repeat the test with the reset time (b) reduced to 50 % of the previous value. Ensure that the second operate
time (c) is 50 % of the first (a) operate time.
Check correct indication, trip output, alarm contacts, waveform record.
Operate
time
(expected)
Reset time
(calculated)
Operate time
(measured)
50 % Reset
Time
(calculated)
50 % operate
time
(calculated)
50 % Operate time
(measured)
First test (c) Second Test (c)