ABB RELION 670 Series Technical Manual page 664

Section 9
Voltage protection
Samples:
Generator
terminal
voltage
Samples:
Generator
neutral point
voltage
Fundamental frequency residual
ANSI06000449 V2 EN-US
Figure 356: Simplified logic diagram for stator ground fault protection
STEFPHIZ (59THD) function can be described in a simplified logical diagram as shown in figure
357. 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.
658
3rd
harmonic
Complex VT3
Fourier
filtering
giving VT3
3rd
harmonic
Complex VN3
Fourier
filtering
giving VN3
voltage
CB Status
Block
Stator
Ground
Fault
detection
3rd
harmonic
Pickup
based
Pickup
and trip
logic
Stator
Ground
Pickup
Fault
detection
95 %
1MRK 502 066-UUS B
TRIP
TRIP3H
TRIPVN
PU3H
PU_VN
en06000449_ansi.vsd
Technical manual