Siemens 7SR242 Duobias, Technical Manual

Page: 290 / 382

Chapter 6) 7SR242 Duobias Commissioning & Maintenance Guide
©2015 Siemens Protection Devices Limited Chapter 6 Page 36 of 62
2.6.2.1 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.
2.6.2.2 Element Blocking
The NPS Overcurrent elements can be blocked by Binary Input Inhibit. This functionality should be checked.
Element BI Inhibits
46IT
46DT
Check correct indication, trip output, alarm contacts, waveform record.
When testing is complete reinstate any of the disabled functions.
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)