phase short-circuit gives a negative sequence current of a magnitude: magnitude =
(1/√3) · fault current.
5.
Increase the injected current and note the value at which the step 1 of the function
operates. Start signal ST1 must be activated when amplitude of the negative sequence
current lies slightly above the start level
I2-1>. Corresponding trip signals TR1 and TRIP is
activated after the pre-set time delay has expired.
Note: Block or disable operation of step 2 when testing step 1 if the injected current
activates the step 2.
6.
Decrease the current slowly and note the reset value.
7.
Connect a trip output contact to a timer.
8.
Set the current to 200% of the start level of the step 1, switch on the current and check
the definite time delay for trip signals TR1 and TRIP. Once the measured negative
sequence current exceeds the set start level
I2-1>, the settable definite timer t1 starts to
count and trip signals is released after the set time delay has elapsed. The same test
must be carried out to check the accuracy of definite time delay for ALARM signal.
Note: The output ALARM is operated by START signal.
9.
If inverse time is selected the trip signals TR1 and TRIP operates after a time
corresponding to the formula:
t s
I
[ ]
(
)
=
− >
⋅
1
2 1
100
2
2
Multiple of Start
K
K
This means that if current jumps from 0 to 2 times start and negative sequence
capability value of generator
K1 is set to 10 s and current start level I2-1> is set to 10% of
rated generator current, then TR1 and TRIP signals operates at time equal to 250 sec ±
tolerance.
10. Repeat the above-described tests for the step 2 of the function excluding the inverse
time testing.
11.
Finally check that start and trip information is stored in the event menu.
Example
The CT ratios
sec
CTprim
CT
for all three phases is 1000 A,
IBase is 1000 A, and the following
secondary currents are applied:
IL1
Ampl = 1.1 A
Angl = 15 deg
IL2
Ampl = 0.6 A
Angl = 97 deg
IL3
Ampl = 1.3 A
Angl = -135 deg
The service value output NSCURR indicating amplitude of negative sequence current in
primary amperes should be 962A approximative.
12.5.16.2
Completing the test
GUID-DA67F057-00AD-4391-B50E-047FD6C16EBB v1
Continue to test another functions or end the test by changing the Test mode setting to Off.
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.
1MRK 502 067-UEN B
Section 12
Testing functionality by secondary injection
177
Commissioning manual
