7SR11 & 7SR12 Commissioning and Maintenance Guide
©2017 Siemens Protection Devices Limited Chapter 6 Page 21 of 72
Calculated Timing values in seconds for TM =1.0
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.
2.4.1.1 ANSI Reset
If the element is configured as an ANSI characteristic, it may have an ANSI reset delay applied.
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 (secs)
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.
2.4.1.2 IEC Reset
If the element is configured as an IEC characteristic, it may have an IEC (decaying) reset delay applied.
IEC reset times from operated condition to fully reset are as follows for zero applied current and Time multiplier
(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 (secs)
IEC-NI
9.7
IEC-VI
43.2
IEC-EI
58.2
80
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.
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)
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