Siemens 7SJ85 - Page 434

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Figure 6-55 Cross-Polarized Voltages for Direction Determination
The following table shows how measurands are assigned for direction-determination purposes in the event of
different types of fault.
Table 6-3 Measurands for Direction Determining
Threshold-
Value
Exceeding
Measuring Element
A B C Ground
Current Voltage Current Voltage Current Voltage Current Voltage
A I
A
V
BC
– – – – – –
B – – I
B
V
CA
– – – –
C – – – – I
C
V
AB
– –
Gnd – – – – – – I
r
V
0
A, Gnd – V
BC
– – – – I
r
V
0
B, Gnd – – I
B
V
CA
– – I
r
V
0
C, Gnd – – – – I
C
V
AB
I
r
V
0
A, B I
A
V
BC
I
B
V
CA
– – – –
B, C – – I
B
V
CA
I
C
V
AB
– –
A, C I
A
V
BC
– – I
C
V
AB
– –
A, B, Gnd I
A
V
BC
I
B
V
CA
– – I
r
V
0
B, C, Gnd – – I
B
V
CA
I
C
V
AB
I
r
V
0
A, C, Gnd I
A
V
BC
– – I
C
V
AB
I
r
V
0
A, B, C I
A
V
BC
I
B
V
CA
I
C
V
AB
– –
A, B, C, Gnd I
A
V
BC
I
B
V
CA
I
C
V
AB
I
r
V
0
Voltage Memory
Saved voltages are used if, when a 3-pole close-up fault occurs, the measuring voltages are not sufficient for
reliable direction determination. Insofar as and as long as no sufficient measuring voltage is available after the
storage time (2 s) has elapsed, the detected direction is retained. If the memory does not contain any voltages
(when closing onto a short circuit, for example), the behavior of the stage is defined using the Non-direc-
tional pickup parameter.
Direction Determination
As mentioned in the General section, the direction is determined by calculating the phase angle between
short-circuit current and reference voltage. To take different system conditions and applications into account,
the reference voltage can be rotated through an adjustable angle (Rotation angle of ref. volt.
parameter). This moves the vector of the rotated reference voltage close to the vector of the short-circuit
Protection and Automation Functions
6.6 Directional Overcurrent Protection, Phases
434 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017