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1MRK 504 165-UEN Rev. K
3.
Check that the trip and alarm contacts operate according to the configuration logic.
4.
Decrease the current slowly from the operate value and note the reset value.
5.
If available on the test set, a second harmonic current of about 20% (assumes 15% default
setting value for I2/I1Ratio parameter) shall be added to the fundamental frequency current in
phase L1. Increase the fundamental frequency current magnitude in phase L1 above the
pickup value measured in step 2. Make sure that trip signal from the PSTPDIF function is not
given. Check that the second harmonic blocking is active in the corresponding phase.
6.
If available on the test set, a fifth harmonic current of about 30% (assumes 25% default setting
value for I5/I1Ratio parameter) shall be added to the fundamental frequency current in phase
L1. Increase the fundamental frequency current magnitude in phase L1 more than the pickup
value measured in step 2. Make sure that trip signal from the PSTPDIF function is not given.
Check that the fifth harmonic blocking is active in the corresponding phase.
7.
Repeat the procedure by injecting current in phases L2 and L3 respectively.
11.3.5.5
Verifying the zero-sequence current reduction from winding two side
1.
Connect the test set for three-phase currents injection to the current terminals of the IED, which
are connected to the CTs on the winding two side of the power transformer.
2.
Inject current in all three phases with equal magnitudes corresponding to the rated load of the
PST (i.e. 100%) in secondary amperes as given below:
I
I njected W
IECEQUATION18059 V1 EN-US
•
•
11.3.5.6
Verifying the three-phase pickup from winding two side
1.
Connect the test set for three-phase currents injection to the current terminals of the IED, which
are connected to the CTs on the winding two side of the power transformer.
2.
Inject symmetrical three-phase currents (for example, positive sequence current only). Increase
the current magnitude symmetrically in all three phases until the protection function operates
and note the operating current. The operating secondary current should have the following
value:
I
P ickup
IECEQUATION18060 V1 EN-US
Transformer protection RET670
Commissioning manual
The pickup current is independent of the actual phase angle shift across the
protected PST.
CTsec
W
2
*
I
_
2
Base W
_
CTprim
W
2
The phase angle for all three injected current on the test set shall have the same
value of zero degree. As a consequence the, PSTPDIF function will work in either
of the following two ways:
Trip, if parameter ZSCurrSubtrW2 = Off and all three differential currents and the bias
current shall be 100%. These values are available as outputs and service values from the
PSTPDIF function.
Not trip, if parameter ZSCurrSubtrW2 = On and all three differential currents and the bias
current shall be 0%. These values are available as outputs and service values from the
PSTPDIF function.
CTsec
W
2
*
IdMin I
*
3
Ph W
CTprim
2
W
2
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2
Base W
_
2
Section 11
Testing functionality by secondary injection
GUID-A87F73CC-76A9-4661-9BA9-E19B902845D6 v1
(Equation 3)
GUID-11BB9D92-941D-4803-A319-578A049A7743 v1
(Equation 4)
99
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