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2.1.5.1 Element Blocking
The Phase Overcurrent elements can be blocked by Binary Input Inhibit and Inrush Detector operation. This
functionality should be checked.
Element
51-1
51-2
50-1
50-2
2.1.5.2 ANSI Reset
If the element is configured as an ANSI characteristic, it may have an ANSI (decaying) 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 Time multiplier
(TM) = 1.0. The reset curve characteristic type and TM is defined by the operating characteristic.
Curve
ANSI-MI
ANSI-VI
ANSI-EI
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
Reset time
(expected)
(calculated)
Check correct indication, trip output, alarm contacts, waveform record.
©2010 Siemens Protection Devices Limited
7SR242 Duobias Commissioning & Maintenance Guide
BI Inhibits
Fully operated to reset with Zero current applied & TM=1 (secs)
Operate time
50% Reset
(measured)
(calculated)
First test (c)
Inrush Detector
4.85
21.6
29.1
50% operate
Time
time
(calculated)
Chapter 6 Page 20 of 57
50% operate
time
(measured)
Second Test (c)
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