Determination of the Ground-Fault Phase
The phase in which the voltage falls below
V< (under-voltage phase threshold for ground-
fault)
is identified as the phase fault, as long as the other 2 phase-to-ground voltages simultaneously
exceeds
V> (over-voltage phase threshold for ground-fault)
.
V< must be set to less than the minimum expected operational phase-to-ground voltage.
V> must be greater than the maximum expected operational phase-to-ground voltage.
If V> and V< are set to zero, these voltages will not be used for fault detection.
i
i
NOTE
V< and V> have no significance in a solidly grounded system.
The following figure shows the ground fault displayed on the HMI with the phase fault.
[dw_sfcmdtcgrndfault, 1, en_US]
Figure 4-17
HMI Display Status
Determination of Repeated Phase Faults with Automatic Reclosing
The device detects and records the repeated phase faults. A repeated phase fault is defined as the phase fault
that occurs due to an automatic reclosing (AREC) as long as the SICAM FCM indicates the fault, that is, it has
not been reset via one of the possible reset mechanisms yet. When a fault occurs, one of the 2 digital outputs
is closed and gets latched (DO1 for forward fault direction and DO2 for reverse fault direction). For a subse-
quent phase fault, one of the 2 digital outputs opens for 100 ms and closes again afterwards.
For every phase fault, the Modbus register (Address 24) is set for 3 s or until the fault current persists. If the
fault current does not persist, the Modbus register is reset for 3 s.
This logic is active only if the DOs are not configured.
For more information about the Modbus register, refer to
.
Intermittent Ground Fault
A typical characteristic of intermittent ground faults is that they often extinguish automatically and strike
again after some time. The fault can last between a few milliseconds and many seconds.
If the ground current (I
N
) exceeds the ground-current threshold (I
N
>) and lasts for time less than tI
N
>, then
pickups are counted. When ground-current pickup counter exceeds the value of
Nos det.
within a configu-
rable time
T det. ext.
, an intermittent ground fault is detected.
The ground-current pickup counter is cleared under the following conditions:
•
If the FCM reboots and when the permanent ground fault occurs, then the ground-current pickup
counter is cleared.
•
If a permanent phase fault has occurred and the fault is reset, then the ground-current pickup counter is
cleared
If ground-current faults get detected multiple times within the fault reset time, the respective digital output
operates for 25 ms (DO1 for forward fault direction and DO2 for reverse fault direction).
4.1.22
4.1.23
4.1.24
Device Functions
4.1 Description
SICAM, Feeder Condition Monitor, Manual
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E50417-H8940-C580-A4, Edition 03.2019