6.3 Testing differential protection functions
6.3.1 Transformer differential protection T3WPDIF
Prepare the IED for verification of settings as outlined in 5.1 "Preparing the IED to
verify settings".
Values of the logical signals for T3WPDIF are available on the local HMI under Main
menu/Tests/Function status/Differential/T3WPDIF(87T,Id)/T3WPDIF:1. The
Signal Monitoring in PCM600 shows the same signals that are available on the local
HMI.
6.3.1.1 Verifying the settings
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 will be different by a factor k from the three-phase start,
see step
7. This factor k can have one of the following three values: 1.0, or 1.5,
or 2.0.
6. Check in the same way the function by injecting current in phases L2 and L3
respectively. Phase L2 and L3 start shall be the same as for phase L1.
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.
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
6. Repeat test with current injection in phases L2 and L3 respectively.
Section 6 1MRK 502 049-UEN A
Testing functionality
44
Commissioning manual
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