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If the phase sequence is clockwise, then it is denoted as ABC. Similarly if the phase sequence is counter-clock-
wise, then it is denoted as ACB. The monitored phase sequence is also displayed as 2 discrete inputs in the
Modbus register.
The following phasor diagram shows the clockwise and counter-clockwise phase sequences:
[dw_sfcm-phasesequence, 1, en_US]
Figure 4-9 Clockwise and Counter-Clockwise Phase Sequences
In the HMI, the status of the phase sequence is shown as PH SEQ: ABC or PH SEQ: ACB or ---, if the phase
sequence cannot be determined.
If the phase sequence is ABC, then the discrete input (33) of the Modbus register is set to 1.
If the phase sequence is ACB, then the discrete input (34) of the Modbus register is set to 1.
If the phase sequence is not detected, then the discrete inputs (33, 34) of the Modbus registers are set to 0.
If the phase-to-ground voltage is below the threshold voltage, then the phase sequence is displayed as --- on
the HMI and the Modbus register is set to 0.
If there are any device alerts and a fault is detected in the system, then the phase sequence is displayed as ---
on the HMI and the Modbus register is set to 0.
i
i
NOTE
Protection functions implemented in SICAM FCM are designed for clockwise phase sequence only.
Determination of Fault Direction
The fault direction for the phase faults is determined by calculating the phase angles between the fault
current and the corresponding phase-to-phase voltages.
Pickup Measuring Element
1
2 3 N
1 I
1
V
2
- V
3
– – – – – –
2 – – I
2
V
3
- V
1
– – – –
3 – – – – I
3
V
1
- V
2
– –
N – – – – – – –
V
NG
6
1, N I
1
V
2
- V
3
– – – – I
N
V
NG
6
2, N – – I
2
V
3
- V
1
– – I
N
V
NG
6
3, N – – – – I
3
V
1
- V
2
I
N
V
NG
6
4.1.15
6
V
NG
= V
1
+ V
2
+ V
3
(derived value)
Device Functions
4.1 Description
SICAM, Feeder Condition Monitor, Manual 41
E50417-H8940-C580-A4, Edition 03.2019