Siemens siprotec 7SD5

2 Functions
300
7SD5 Manual
C53000-G1176-C169-1
Figure 2-128 Connection example with external protection device for fault detection depen-
dent dead time — dead time control by pickup signals of the protection device;
AR control mode = with PICKUP
2 Protection Relays
with 2 Automatic
Reclosure Circuits
If redundant protection is provided for a line and each protection operates with its own
automatic reclosure function, a certain signal exchange between the two combinations
is necessary. The connection example in Figure 2-129 shows the necessary cross-
connections.
If phase segregated auxiliary contacts of the circuit breaker are connected, a three-
pole coupling by the 7SD5 is guaranteed when more than one CB pole is tripped. This
requires activation of the forced three-pole trip (see Section 2.15.2 at margin heading
„Forced Three-Pole Trip“). An external automatic three-pole coupling is therefore not
necessary when the above conditions are satisfied. This rules out two-pole tripping
under all circumstances.
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