Restricted Earth Fault Protection, Low Impedance Refpdif (87N); Verifying The Settings; Completing The Test; Additional Security Logic For Differential Protection Ldrgfc (11) - ABB RET670 Commissioning Manual

Section 11
Testing functionality by secondary injection
11.3.3
11.3.3.1
11.3.3.2
11.3.4
11.3.4.1
110
Restricted earth fault protection, low impedance REFPDIF
(87N)
Prepare the IED for verification of settings outlined in Section
verify settings".

Verifying the settings

1. Connect the test set for single-phase current injection to the protection terminals
connected to the CT in the power transformer neutral-to-ground circuit.
2. Increase the injection current and note the operating value of the protection
function.
3. Check that all trip and pickup signals appear according to the configuration logic.
4. Decrease the current slowly from operate value and note the reset value.
5. Connect the timer and set the current to ten times the value of the IdMin setting.
6. Switch on the current and note the operate time.
7. Connect the test set to terminal A and neutral of the three-phase current input
configured to REFPDIF (87N). Also inject a current higher than half the IdMin
setting in the neutral-to-ground circuit with the same phase angle and with polarity
corresponding to an internal fault.
8. Increase the current injected in A, and note the operate value. Decrease the current
slowly and note the reset value.
9. Inject current into terminals B and C in the same way as in step 7 above and note the
operate and reset values.
10. Inject a current equal to 10% of rated current into terminal A.
11. Inject a current in the neutral-to-ground circuit with the same phase angle and with
polarity corresponding to an external fault.
12. Increase the current to five times the operating value and check that the protection
does not operate.
13. Finally check that trip information is stored in the event and disturbance recorder.

Completing the test

Continue to test another function or end the test by changing the TESTMODE setting to
Disabled. Restore connections and settings to their original values, if they were changed
for testing purposes.

Additional security logic for differential protection LDRGFC (11)

Verifying the settings
1MRK 504 165-UUS -
"Preparing the IED to
Transformer protection RET670 2.2 ANSI
Commissioning manual