7SR242 Duobias Commissioning & Maintenance Guide
©2010 Siemens Protection Devices Limited Chapter 6 Page 23 of 57
2.2.2.1 Element Blocking
The Measured Earth Fault elements can be blocked by Binary Input Inhibit, VT Supervision and Inrush Detector
operation. The Characteristic can be made non-directional by VT Supervision. This functionality should be
checked.
Element BI Inhibits Inrush Detector
51N-1
51N-2
51N-3
51N-4
50N-1
50N-2
50N-3
50N-4
2.2.3 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 (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.
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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