12.3.1.1
Verifying the settings
SEMOD54284-51 v10
1.
Go to Main menu/Test/Function test modes/Differential protection and make sure that
the restricted earth fault protection, low impedance function REFPDIF is set to
Off and
that the four step residual overcurrent function EF4PTOC under Main menu/Test/
Function test modes/Current protection is set to
Off, since they are configured to the
same current transformer inputs as the transformer differential protection. Make sure
that the transformer differential functions T2WPDIF or T3WPDIF are unblocked.
2.
Connect the test set for injection of three-phase currents to the current terminals of the
IED, which are connected to the CTs on the HV side of the power transformer.
3.
Increase the current in phase L1 until the protection function operates and note the
operating current.
4.
Check that the trip and alarm contacts operate according to the configuration logic.
5.
Decrease the current slowly from operate value and note the reset value.
Depending on the power transformer vector group (Yd and so on), the single-phase
injection current may appear as differential current in one or two phases and the
operating value of the injected single-phase current will be different.
6.
Check in the same way the function by injecting current in phases L2 and L3 respectively.
7.
Inject a symmetrical three-phase current and note the operate value.
8.
Connect the timer and set the current to twice the operate value.
9.
Switch on the current and note the operate time.
10. Check in the same way the measuring circuits connected to the CTs on the LV side and
other current inputs to the transformer differential protection.
11.
Finally check that trip information is stored in the event menu.
Information on how to use the event menu is found in the operator’s
manual.
12.
If available on the test set, a second harmonic current of about 20% (assumes 15%
setting on I1/I2 ratio parameter) can be added to the fundamental frequency in phase L1.
Increase the current in phase L1 above the start value measured in step
with current injection in phases L2 and L3 respectively.
The balancing of currents flowing into and out of the differential zone is checked by
primary injection testing, see
section "Requirements" and section "Preparing for test" in
this chapter.
Fifth harmonic blocking can be tested in a similar way.
For more detailed formulas please refer to the application manual.
12.3.1.2
Completing the test
SEMOD54284-86 v5
Continue to test another function or end the test by changing the
TestMode setting to Off.
Restore connections and settings to their original values, if they were changed for testing
purposes.
12.3.2
High impedance differential protection HZPDIF
SEMOD55257-42 v3
Prepare the IED for verification of settings as outlined in section
in this chapter.
12.3.2.1
Verifying the settings
SEMOD55257-46 v5
1MRK 502 067-UEN B
Section 12
Testing functionality by secondary injection
99
Commissioning manual
