Siemens SIPROTEC Manual page 121

Pickup modes
The adaptation to different network conditions is determined by pickup modes.
The setting (PROGAM U/I) determines whether the phase–to-phase loops or the phase–to-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–to-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 cur-
rents the pickup threshold will be higher. This applies in particular if the network neutral is earthed low–resis-
tance. If only the phase-to-earth loops are evaluated, it must be ensured that the overcurrent stage Iph>> re-
sponds in the event of phase-to-phase faults. If only one measuring system picks up, it can be decided whether
this will result in a pickup of the phase-to-earth loops or the phase-to-phase loops in the earthed network (see
Table 2-5).
Table 2-5
Pickup
Module
L1
L2
L3
L1
L2
L3
L1
L2
L3
1)
Only active for earthed power systems
When evaluating the phase-to-phase loops, the sensitivity is particularly high for phase-to-phase faults. In ex-
tensive 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 con-
ditions, i.e. in 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–to-phase loops are evaluated, the measuring loop is
independent of the earth-fault detection, therefore this procedure is not suitable for earthed networks (see Table
2-6).
Table 2-6
Pickup
Module
L1
L2
L3
If the option has been chosen whereby voltage loop selection is dependent on earth-fault detection, then high
sensitivity applies to phase-to-earth faults and to phase–to-phase faults. On principle, this option is indepen-
dent of the treatment of the network neutral, however, it requires that the earth–fault criteria according to
Section Earth Fault Detection are met for all earth faults or double earth faults (see Table 2-7).
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
Loops and phase indications for single-phase overcurrent pickup U/I; Phase-to-earth voltages
program
Measuring Measur-
Current ing
Voltage
L1 L1-E
L2 L2-E
L3 L3-E
L1 L1-E
L2 L2-E
L3 L3-E
L1 L1-E
L2 L2-E
L3 L3-E
Loops and phase indications for single-phase overcurrent pickup U/I; Phase-to-phase voltages
program
Measuring Measur-
Current ing
Voltage
L1 L1-L2
L2 L2-L3
L3 L3-L1
Earth Fault Parameter
Detection 1ph FAULTS
no
phase-to-
no
phase
no
no
phase-to-earth
no
1)
no
yes
yes any
yes
Earth Fault Parameter
Detection 1ph FAULTS
any any
2.5 Distance Protection
Valid Alarmed
Loop Phase(s)
L3-L1 L1, L3
L1-L2 L1, L2
L2-L3 L2, L3
L1-E L1
L2-E L2
L3-E L3
L1-E L1, E
L2-E L2, E
L3-E L3, E
Valid Alarmed
Loop Phase(s)
L1-L2 L1, L2
L2-L3 L2, L3
L3-L1 L1, L3
Functions
121