Functions
2.30 100-%-Stator Earth Fault Protection with 3rd Harmonics (ANSI 27/59TN 3rd Harm.)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
217
Figure 2-93 Automatic Lowering of Pickup Value U0 3.HARM>
The trip characteristic is released as soon as the settable minimum active power is reached. As an additional
security feature, the following limitation is provided: If due to the power-dependent correction factor the correct-
ed pickup value U
3H, corrected
drops below the minimum possible setting value (0,2 V), the pickup value will be
kept at that setting value.
Not connected/Uen-winding; calculation of U
0
Just as for the connection to the broken delta winding, an increase of the 3rd harmonic during a fault also results
for the calculated voltage. The 5203 U0 3.HARM> parameter is also relevant.
Connected to any transformer; Rotor
With these connection types, 100% stator earth fault protection is ineffective.
The following figure shows the logic diagram for the 100 % stator earth fault protection function.
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