Two-Phase Overcurrent Protection (Only Non-Directional) - Siemens SIPROTEC 4 7SJ61 Manual

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
Internal indication
50-3 B PU
50-2 B PU
50-1 B PU
51 B PU
50-3 C PU
50-2 C PU
50-1 C PU
51 C PU
50N-3 PU
50N-2 PU
50N-1 PU
51N PU
50-3 A PU
50-3 B PU
50-3 C PU
50N-3 PU
50-2 A PU
50-2 B PU
50-2 C PU
50N-2 PU
50-1 A PU
50-1 B PU
50-1 C PU
50N-1 PU
51 A PU
51 B PU
51 C PU
51N PU
(All pickups)
In the trip signals, the element which initiated the tripping is also indicated.

Two-phase Overcurrent Protection (Only Non-Directional)

2.2.8
The 2-phase overcurrent protection functionality is used in isolated or grounded systems where interaction
with existing 2-phase protection equipment is required. As an isolated or grounded system remains opera-
tional with a 1-phase ground fault, this protection serves to detect double ground faults with high ground
fault currents. The respective feeder must be switched off only in this case. A 2-phase measurement is suffi-
cient for this purpose. In order to ensure selectivity of the protection in this section of the system, only phases
A and C are monitored.
If 250 50/51 2-ph prot (settable in P.System Data 1) is set to ON, Ι
ison. If the fault is a simple ground fault in B, the element will not pick up. A double ground fault is assumed
only after pickup on A or C, causing the element to pick up and trip after the delay time has elapsed.
NOTE
i
i
With inrush detection activated and inrush only on B, no cross blocking will take place in the other phases.
On the other hand, if inrush with cross blocking is activated on A or C, B will also be blocked.
58
Figure
Figure 2-5
50/51 Ph B PU
Figure 2-7
Figure 2-11
Figure 2-5
50/51 Ph C PU
Figure 2-7
Figure 2-11
Figure 2-6
50N/51NPickedup
Figure 2-9
Figure 2-12
50-3 picked up
50N-3 picked up
Figure 2-5
Figure 2-5
50-2 picked up
Figure 2-5
Figure 2-6
50N-2 picked up
Figure 2-7
Figure 2-7
50-1 picked up
Figure 2-7
Figure 2-6
50N-1 picked up
Figure 2-11
Figure 2-11
51 picked up
Figure 2-11
Figure 2-12
51N picked up
50(N)/51(N) PU
Output indication
is not used for threshold compar-
B
SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016
FNo.
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1761