Siemens siprotec 7SA522 User Manual page 173

Three-pole
Coupling
7SA522 Manual
C53000-G1176-C119-2
Address  5HVHW 7ULS &0' determines which criteria allow for the reset of an
issued trip command. The setting &XUUHQW2SHQ3ROH ensures that the trip command
resets after the current disappears. The measured current must drop below the value
set in address  3ROH2SHQ&XUUHQW before the trip command resets (see above).
With the setting &XUUHQW $1' &% the circuit breaker auxiliary contact must addition-
ally indicate that the circuit breaker has opened. This setting demands that the status
of the auxiliary contacts is marshalled to a binary input.
Address  SROH FRXSOLQJ determines whether each trip command resulting
from fault detection in more than one phase is three-pole, or if three-pole coupling of
the trip command only results when more than one phase is tripped. This setting is
only relevant with one- and three-pole tripping and therefore only available in this ver-
sion. Additional information can be found in Section 6.17.3 fault detection logic of the
device.
With the setting ZLWK 3,&.83 every fault detection in more than one phase leads to
three-pole coupling of the trip outputs, even if only a single-phase earth fault is situated
within the tripping region, and further faults only affect the higher zones, or are located
in the reverse direction. Even if a single-phase trip command has already been issued,
each further fault detection will lead to three-pole coupling of the trip outputs.
If, on the other hand, this address is set to ZLWK 75,3, three-pole coupling of the trip
output (three-pole tripping) only occurs when more than one pole is tripped . Therefore
if a single-phase fault is located within the zone of tripping, and a further arbitrary fault
is outside the tripping zone, single-phase tripping is possible. Even a further fault dur-
ing the single-pole tripping will only cause three-pole coupling if it is located within the
tripping zone.
This parameter is only available in the single- and three-pole tripping version. It ap-
plies to all protection functions of the 7SA522, which can trip single-pole.
The difference made by this parameter becomes apparent when multiple faults are
cleared, i.e. faults occurring almost simultaneously at different locations in the net-
work.
If, as shown in the example (Figure 6-13), two single phase to ground faults occur on
different lines – in this example parallel lines – the protection relays on the two faulted
lines, at all four line ends, pick up. In this example, all four relays detect a L1-L2-E
fault, in other words a two phase to ground fault. However, each individual line is only
subjected to a single phase to ground fault. If single pole tripping and reclosure is em-
ployed, it is therefore desirable that each line only trips and recloses single pole. This
is achieved by setting  3pole coupling to with TRIP . In this manner each of the
four relays at the four line ends recognises that single pole tripping for the fault on the
respective line is required.
Multiple fault on a double-circuit line
Figure 6-13
L1–E
L2–E
Functions
6-25