ABB Relion Technical Manual page 322

Section 9
Voltage protection
316
Samples:
Generator
3rd
terminal
harmonic
voltage
Fourier
filtering
giving VT3
Samples:
Generator
3rd
neutral point
harmonic
voltage
Fourier
filtering
giving VN3
Fundamental frequency residual
voltage
52a
BLOCK
ANSI10000240 V2 EN
Figure 145: Simplified logic diagram for stator ground fault protection
STEFPHIZ (59THD) function can be described in a simplified logical diagram as shown
in figure 146. Note that the 3rd harmonic numerical filters are not part of the stator ground-
fault protection function.
These third harmonic voltages are calculated by the preprocessing blocks connected to the
function.
Stator
Complex VT3
Ground
Fault
detection
3rd
harmonic
based
Complex VN3
Stator
Ground
Fault
detection
95 %
1MRK 502 048-UUS A
TRIP
TRIP3H
TRIPVN
Pickup
Pickup
and trip
logic PU3H
PU_VN
PICKUP
Pickup
ANSI10000240-2-en.vsd
Technical manual