Siemens siprotec 7SA6 User Manual page 228

Functions
6-46
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,
• acyclic L1 before L3 before L2,
• acyclic L2 before L1 before L3,
• acyclic L1 before L2 before L3,
• acyclic L3 before L2 before L1,
• acyclic L2 before L3 before L1,
• 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) $OO ORRSV.
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 $OO ORRSV.
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
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
L1–E, L2–E, (L1–L2)
L2–E, L3–E, (L2–L3)
L1–E, L3–E, (L3–L1)
short form: / / DF\FOLF;
short form: / / DF\FOLF;
short form: / / DF\FOLF;
short form: / / DF\FOLF;
short form: / / DF\FOLF;
short form: / / DF\FOLF;
Evaluated
Loop(s)
L1–E
L3–E
L3–E
L1–E
L3–E
L1–E
L2–E
L2–E
L1–E
L1–E
L2–E
L1–E
L2–E
L3–E
L3–E
Setting
Parameter 1221
3+$6( 35()SKH =
/ / DF\FOLF
3+$6( 35()SKH =
/ / DF\FOLF
3+$6( 35()SKH =
/ / DF\FOLF
3+$6( 35()SKH =
/ / DF\FOLF
3+$6( 35()SKH =
/ / DF\FOLF
7SA6 Manual
C53000-G1176-C133-1