ABB 615 Series - Page 373

Residual current Io and residual voltage VG
FEEDER
FEEDER MEAS
IGv
Fault
Point
K
R
e
-0.3
-0.2
-0.1
Residual Current (kA) Residual Voltage x 10
2
(kV)
INCOMER
COMP. COIL
IGj
VG
K
R
e
0
0.1
IGj
(Faulty
Feeder)
IGv
(Healthy
Feeder)
VG
Pulsewidth
400‐800

s
Pulseinterval
5‐300ms
Peakvalue
~0.1...5kA
U
tres
U
tres
I
ctot
R
f
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.
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 367
Technical Manual