Siemens siprotec 7SD5 User Manual

2.5 Distance Protection
125
7SD5 Manual
C53000-G1176-C169-1
diff). Another way of blocking the zone is to set a binary input (No 3610 „>BLOCK
Z1-Trip“).
Switching onto a
Fault
If the circuit breaker is manually closed onto a short circuit, the distance protection can
issue an instantaneous trip command. By setting parameters it may be determined
which zone(s) is/are released following a manual close (refer to Figure 2-39). The line
energization information (input „SOTF“) is derived from the state recognition.
Figure 2-39 Switching onto a fault
Note
When switching onto a three-pole fault with the MHO characteristic, there will be no
voltage in the memory or unfaulted loop voltage available. To ensure fault clearance
when switching onto three-pole close-up faults, please make sure that in conjunction
with the configured MHO characteristic the instantaneous tripping function is always
enabled.
2.5.1.4 Setting Notes
At address 1501 FCT Distance the distance protection function can be switched ON
or OFF.
Minimum Current The minimum current for fault detection Minimum Iph> (address 1502) in case of
impedance pickup is set somewhat (approx. 10 %) below the minimum short-circuit
current that may occur. For the other pickup modes it is set at address 1911.
Earth Fault
Detection
In systems with earthed starpoint, the setting 3I0> Threshold (address 1503) is
set somewhat below the minimum expected earth fault current. 3I
0
is defined as the
sum of the phase currents |I
L1
+ I
L2
+ I
L3
|, which equals the starpoint current of the set
of current transformers. In non-earthed systems the setting value is recommended to
be below the earth current value for double earth faults.
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Siemens siprotec 7SD5 Specifications

General

Brand	Siemens
Model	siprotec 7SD5
Category	Relays
Language	English