ABB 615 series Technical Manual page 373

1MAC059074-MB A
615 series ANSI
Technical Manual
Residual current Io and residual voltage VG
COMP. COIL
R e R e
K K
FEEDER MEAS
FEEDER
INCOMER
VG
I IGv
IGj
ctot
Fault
Point
U
U tres
tres
GUID-10F6E368-89A9-426D-908D-B92EF2988BE4 V1 EN
Figure 172: Typical intermittent ground-fault characteristics
Ground-fault transients
In general, ground faults generate transients in currents and voltages. There are several
factors that affect the magnitude and frequency of these transients, such as the fault
moment on the voltage wave, fault location, fault resistance and the parameters of the
feeders and the supplying transformers. In the fault initiation, the voltage of the faulty
phase decreases and the corresponding capacitance is discharged to ground (→ discharge
transients). At the same time, the voltages of the healthy phases increase and the related
capacitances are charged (→ charge transient).
If the fault is permanent (non-transient) in nature, only the initial fault transient in current
and voltage can be measured, whereas the intermittent fault creates repetitive transients.
IGv
(Healthy
Feeder)
0.1
0
-0.1
-0.2
R
IGj
f
(Faulty
Feeder)
-0.3
Section 4
Protection functions
VG
Pulse width
400 ‐ 800 s
Pulse interval
5 ‐ 300 ms
Peak value
~0.1 ... 5 kA
367