Technical Guide
Testing self-powered relays with SVERKER 900
Page 26(33)
Figure 29. Short description of the functionality of MTT in pre-fault and fault instrument (from the SVERKER 900
user’s manual [13], Copyright Megger).
In MTT the following major settings are necessary:
Pre-fault level:
0,5 A duration t = 1000 ms
First fault level:
1,5 A max duration t = 20 s
(this timer could be increased if higher operate times may be measured,
especially if the no-trip condition needs to be considered)
Binary Input (BI):
set to contact sensing
no particular adjustments are necessary for the debounce time than can be
kept as default.
(in principle any of the 4 available BIs of SVERKER 900 could be used)
6.2.4. Testing the overcurrent protection function.
Considering the information in par. 6.2.3, set up the necessary conditions in SVERKER 900 and run the
sequence of tests
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. Each pre-fault and fault sequence is started by pressing the knob. Once the operate time is
recorded by the SVERKER 900, just rotate the knob to change the fault level, and press it again to inject it. Until
you have finished with the sequence of tests. Figure 30, Figure 31 and Figure 32 show the most important
points. Also the tests for WIC-1 relay (par. 5.2.4) details about this procedure.
Also for WIP relay, please make sure you perform the non-trip test of the thresholds, i.e. foresee tests at 1 A for
verifying the non-trip of I> and tests at 4,5 A to verify non-trip of (I>>). In this last case, of course there will be
the trip from I>, reasonably higher than the time delay of I>>. See par. 4.1.3 for details.
Please keep in mind what said in par. 4.1.3
for the “no trip tests” and for the “distance” from the thresholds.
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As no earth fault relay is activated, it is indifferent from the protection functionality point of view, if single-phase injections or
three phase injections are executed. This document shows tests executed with single-phase injection, but it is possible of
course to execute three-phase faults in order to avoid the activation of the earth fault.
