Functions
6-46 7SA6 Manual
C53000-G1176-C133-1
There are special measures against such undesirable pick-ups (see Subsection
6.2.1).
With the occurrence of a double earth fault in isolated or resonant-earthed systems it
is sufficient to switch off one of the faults. The second fault may remain in the system
as a simple earth fault. Which of the faults is switched off depends on the double earth
fault preference which is set the same in the whole galvanically-connected system.
With 7SA6 the following double earth fault preferences 3+$6(35()SKH can be
selected:
• acyclic L3 before L1 before L2, short form: //DF\FOLF;
• acyclic L1 before L3 before L2, short form: //DF\FOLF;
• acyclic L2 before L1 before L3, short form: //DF\FOLF;
• acyclic L1 before L2 before L3, short form: //DF\FOLF;
• acyclic L3 before L2 before L1, short form: //DF\FOLF;
• acyclic L2 before L3 before L1, short form: //DF\FOLF;
• cyclic L3 before L1 before L2 before L3, short form: //F\FOLF;
• cyclic L1 before L3 before L2 before L1, short form: //F\FOLF;
• all loops are measured (no preference) $OOORRSV.
In all eight preference options one earth fault is switched off according to the
preference scheme. The second fault can remain in the system as a simple earth fault.
It can be detected with the ordering option “Earth Fault Detection in Non-earthed
Systems” (see Section 6.11).
The 7SA6 also enables the user to switch off both fault locations of a double earth
fault. Set the double earth fault preference to $OOORRSV.
Table 6-8 lists all measured values used for the distance measuring in isolated or
resonant-earthed systems.
Table 6-8 Evaluation of measured loops for a multiple pick-up in non-earthed systems
Fault detection
Loops
Evaluated
Loop(s)
Setting
Parameter 1221
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L1–E
L3–E
L3–E
3+$6(35()SKH =
//DF\FOLF
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L1–E
L3–E
L1–E
3+$6(35()SKH =
//DF\FOLF
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L2–E
L2–E
L1–E
3+$6(35()SKH =
//DF\FOLF
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L1–E
L2–E
L1–E
3+$6(35()SKH =
//DF\FOLF
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L2–E
L3–E
L3–E
3+$6(35()SKH =
//DF\FOLF
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