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Section 11
Testing functionality 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 /IED Settings/Current protection /NegSeqOverCurr2Step/
NSOn /General and make sure that the function is enabled, that is Operation is set to On.
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 start 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 used. A two 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:
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
currents are applied:
IL1
IL2
IL3
186
[ ]
t s
CTprim
CT
sec
for all three phases is 1000 A, IBase is 1000 A, and the following secondary
Ampl = 1.1 A
Ampl = 0.6 A
Ampl = 1.3 A
© 2017 - 2022 Hitachi Energy. All rights reserved
1
− >
2
2 1
I
100
=
⋅
K K
(
)
2
Multiple of Start
1MRK 504 165-UEN Rev. K
Angl = 15 deg
Angl = 97 deg
Angl = -135 deg
Transformer protection RET670
Commissioning manual
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