Completing The Test; Negative-Sequence Time Overcurrent Protection For Machines Ns2Ptoc (46I2); Verifying Settings By Secondary Injection - ABB RET670 Commissioning Manual

Section 11
Testing functionality by secondary injection
11.5.13.2
11.5.14
11.5.14.1
206
Note that it is recommended to test IDMT operating times by injected
current with the rated frequency.
Above procedure can also be used to test definite time step. Pay attention that IDMT step
can also trip during such injection. Therefore make sure that appropriate settings are
entered in order to insure correct test results for definite time step.

Completing the test

Continue to test another functions or end the test by changing the Test mode setting to
Disabled. Restore connections and settings to their original values, if they were changed
for testing purposes. Make sure that all built-in features for this function, which shall be
in operation, are enabled and with correct settings.
Negative-sequence time overcurrent protection for machines
NS2PTOC (46I2)
When inverse time overcurrent characteristic is selected, the trip time of
the stage will be the sum of the inverse time delay and the set definite time
delay. Thus, if only the inverse time delay is required, it is important to set
the definite time delay for that stage to zero.

Verifying settings by secondary injection

1. Connect the test set for injection of three-phase currents to the appropriate current
terminals of the IED.
2. Go to Main menu/Settings/Setting group n/Current protection/
NegSeqOverCurr2Step/NSOn/General and make sure that the function is
enabled, that is Operation is set to Enabled.
3. Inject current into IEDs in such a way that negative sequence component is created
and then verify that negative sequence component of the injected currents is
calculated correctly by the function. See example below for 1 A rated current
transformer.
4. Inject pure negative sequence current, that is, phase currents with exactly same
magnitude, reversed sequence and exactly 120° phase displaced into the IED with an
initial value below negative sequence current pickup level. No output signals should
be activated.
Note: If it is difficult to obtain pure negative sequence current for the secondary
injection test, a current corresponding to the two phase short-circuit condition can be
1MRK 504 165-UUS -
Transformer protection RET670 2.2 ANSI
Commissioning manual