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• Change to the »Measuring Values« menu.
• Check the measuring value for the unbalanced current »I2 Fund.«. The measuring
value displayed for »I2 Fund.« should be zero (within the physical measuring
accuracy).
NOTICE!
If the displayed magnitude for I2 Fund. is the same as that for the balanced nominal
currents fed to the relay, it implies that the phase sequence of the currents seen by the
relay is reversed.
Now turn-off phase A.
• Again check the measuring value of the unbalanced current »I2 Fund.« in
the »Measuring Values« menu.The measuring value of the unbalanced current »I2
Fund.« should now be 33%.
• Turn-on phase A, but turn-off phase B.
• Once again check the measuring value of the unbalanced current I2 Fund. in
the »Measuring Values« menu. The measuring value of the asymmetrical current »I2
Fund.« should be again 33%.
• Turn-on phase B, but turn-off phase C.
• Again check the measuring value of unbalanced current »I2 Fund.« in
the »Measuring Values« menu. The measuring value of the unbalanced current »I2
Fund.« should still be 33%.
Testing the trip delay:
Apply a balanced three-phase current system (nominal currents).
• Switch off IA (the threshold value »Threshold« for »I2 Fund.« must be below 33%).
• Measure the tripping time.
The present current unbalance »I2 Fund.« corresponds with 1/3 of the existing phase
current displayed.
Testing the threshold values
• Configure minimum »%(I2/I1)« setting (2%) and an arbitrary threshold
value »Threshold« (I2 Fund.).
• For testing the threshold value, a current has to be fed to phase A which is lower
than three times the adjusted threshold value »Threshold« (I2 Fund.).
• Feeding only phase A results in »%(I2/I1) = 100%«, so the first condition »%(I2/I1)
>= 2%« is always fulfilled.
• Now increase the phase A current until the relay is activated.
Testing the dropout ratio of the threshold values
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EMR-3MP0
4 Protective Elements
4.10 46 - Current Unbalance Protection