Siemens siprotec 7SA6 User Manual page 215

Pick-up Mode
7SA6 Manual
C53000-G1176-C133-1
U
V
Load arrea
60
50
U(I>>)
40
U(I>)
30
20
10
Iph>
1
Figure 6-19 U/I characteristic
The setting  (352* 8,) determines if the phase–earth loops or the phase–
phase loops are always valid or if this depends on the earth-fault detection according
to Section 6.2.1. This allows a very flexible adaptation to the network conditions. The
optimum selection mainly depends on whether the network neutral is not earthed
(isolated or compensated), is earthed low–resistance ("semi–solidly") or solid-earthed
(see Section 6.2.3). Setting notes are given in Section 6.2.2.4.
The evaluation of phase–earth loops is characterized by a high sensitivity in the event
of earth faults and is highly advantageous in networks with earthed star points. It
automatically adapts to the prevailing infeed conditions; i.e. in the weak-infeed
operation mode it becomes more current-sensitive, with high load currents the pick-up
threshold will be higher. This applies in particular if the network star-point is earthed
low–resistance. If only the phase–earth loops are evaluated, it must be ensured that
the overcurrent stage ,SK!! responds in the event of phase–phase faults. If only one
measuring system picks up, it can be decided whether this shall result in a pick-up of
the phase–earth loops or the phase–phase loops in the earthed network (see Table 6-
3).
Tabelle 6-3 Loop and phase indication for single-phase
Phase–earth voltage program
Pick-up Measured Measured
module current
L1 L1
L2 L2
L3 L3
L1 L1
L2 L2
L3 L3
L1 L1
L2 L2
L3 L3
1
) Only effective in earthed networks
Short-circuit
area
Iph>>
2
Earth–fault
voltage detection
L1–E no
L2–E no
L3–E no
L1–E no
L2–E no
L3–E no
L1–E yes
L2–E yes
L3–E yes
I
I
N
U/I pickup
;
Parameter Valid
3K )$8/76
loop
L3–L1
Phase–phase L1–L2
L2–L3
L1–E
1
Phase–earth ) L2–E
L3–E
L1–E
any L2–E
L3–E
Functions
Signalled
Phase(s)
L1, L3
L1, L2
L2, L3
L1
L2
L3
L1, E
L2, E
L3, E
6-33