Manual 37138C
ESDR 4T - Current Differential Protection Relay
Page 36/46
© Woodward
Renewed Test with the Correct Connection
(Measurement of the maximum differential currents.)
Restart the unit after restoring the original connections. Test the differential current and the restraint current at
20 % of the rated current and compare these with the values measured from "Testing for Correct Connection". If
the measurements match, you can slowly increase the current up to the rated current. The differential currents
should be approximately zero until they reach the rated current. If this is not the case (e. g. with tapped trans-
formers), the threshold value of the differential protection may have to be corrected to less sensitive values.
Determining the maximum differential currents during fault-free operation should give a starting point for work-
ing out the tripping characteristic (kick point).
•
Start the short-circuited generator in de-energized condition
•
Select the display of the differential currents by pressing the "Display" button (green "Differential current
I
d
" LED must light up)
•
Next gradually increase the generator from a de-energized condition to 1.2 times the rated current and re-
cord the restraint currents and related differential currents
•
Set the threshold values of the tripping characteristic
