Technical Guide
Testing self-powered relays with SVERKER 900
Page 15(33)
For testing the phase overcurrent protection function the instrument MTT [12] of pre-fault and fault and the
possibility to draw graphs of time curves is used
9
[13].
shows an extract of the SVERKER 900 user’s manual where the functionality of MTT in pre-fault and
fault instrument is described.
Figure 13. 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:
0,25 A duration t = 1000 ms
First fault level:
0,8 A max duration t = 10 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):
use BI1 and set is as shown in Figure 12
5.2.4. Testing the overcurrent protection function.
Considering the information in par. 5.2.3, set up the necessary conditions in SVERKER 900 and run the
sequence of tests
10
.
Before the sequence of the tests is run, consider a no-trip test at a current level of approximately 0,55 A
(roughly 90% of the threshold, 0,6 A, see par. 4.1.3). Consider to increase the time-out to some 30 seconds
(
“Max” in fault state) to avoid the risk of declaring no-trip only because a very short time-out was set.
Set in MTT pre-fault and fault the pre-fault values (Figure 14):
9 Note that not all SVERKER 900 are equipped with this functionality, please contact Megger for details.
10 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.
