Siemens siprotec 7SD5 User Manual

2.5 Distance Protection
115
7SD5 Manual
C53000-G1176-C169-1
Pickup Modes The adaptation to different network conditions is determined by pickup modes.
The setting (PROGAM U/I) determines whether the phase–phase loops or the phase–
earth loops are always valid, or whether this depends on the earth fault detection. This
allows a very flexible adaptation to the network conditions. Optimum control mainly
depends on whether the network neutral is not earthed (isolated or compensated), has
a low–resistance or effective earthing. Setting notes are given in Section 2.5.1.4.
The evaluation of phase–earth loops is characterized by a high sensitivity in the event
of earth faults and is therefore highly advantageous in networks with earthed
star
points. It automatically adapts to the prevailing infeed conditions; i.e. in the weak-
infeed operation mode it becomes more current-sensitive, with high load currents the
pickup threshold will be higher. This applies in particular if the network neutral is
earthed low–resistance. If only the phase-earth loops are evaluated, it must be
ensured that the overcurrent stage Iph>> responds in the event of phase-phase
faults. If only one measuring system picks up, it can be decided whether this will result
in a pickup of the phase-earth loops or the phase-phase loops in the earthed network
(see Table 2-5).
Table 2-5 Loops and phase indications for single-phase overcurrent pickup U I; Phase-to-
earth-voltages program
1)
only active for earthed power systems
When evaluating phase–phase loops, the sensitivity towards phase–phase faults is
particularly high. In extensive compensated
networks this selection is advantageous
because it excludes pickup as a result of single earth faults on principle. With two- and
three-phase faults it automatically adapts to the prevailing infeed conditions, i.e. in the
weak-infeed operation mode it becomes more current-sensitive, with strong infeed
and high load currents the pickup threshold will be higher. If only phase-phase faults
are evaluated, the measuring loop is independent of the earth-fault detection, there-
fore this procedure is not suitable for earthed networks
(see Table 2-6).
Table 2-6 Loops and phase indications for single-phase overcurrent pickup U I; Phase-to-
earth-voltages program
Pickup
module
Measur-
ing
Current
Measur-
ing
Voltage
Earth fault
detection
Parameter
1ph FAULTS
Valid
Loop
Alarmed
Phase(s)
L1
L2
L3
L1
L2
L3
L1-E
L2-E
L3-E
No
No
No
phase–phase
L3-L1
L1-L2
L2-L3
L1, L3
L1, L2
L2, L3
L1
L2
L3
L1
L2
L3
L1-E
L2-E
L3-E
No
No
No
phase-earth
1)
L1-E
L2-E
L3-E
L1
L2
L3
L1
L2
L3
L1
L2
L3
L1-E
L2-E
L3-E
Yes
Yes
Yes
any
L1-E
L2-E
L3-E
L1, E
L2, E
L3, E
Pickup
module
Measur-
ing
Current
Measur-
ing
Voltage
Earth Fault
Detection
Parameter
1ph FAULTS
Valid
Loop
Alarmed
Phase(s)
L1
L2
L3
L1
L2
L3
L1-L2
L2-L3
L3-L1
any any
L1-L2
L2-L3
L3-L1
L1, L2
L2, L3
L1, L3
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Siemens siprotec 7SD5 Specifications

General

Brand	Siemens
Model	siprotec 7SD5
Category	Relays
Language	English