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Functions
2.5 Distance Protection
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
176
2.5.4 Tripping Logic of the Distance Protection
2.5.4.1 Method of Operation
General pickup
Using the fault detection modes I , U/ I or U/ I /
ϕ
, the signal
„Dis. PICKUP“
(general pickup of the distance pro-
tection function) is generated after the pickup as soon as one of the conditions for pickup is fulfilled. As soon
as any of the distance zones has determined with certainty that the fault is inside the tripping range, the signal
„Dis. PICKUP“
is generated when using the impedance pickup.
The signal
„Dis. PICKUP“
is reported and made available for the initialisation of internal and external sup-
plementary functions (e.g. teleprotection signal transmission, automatic reclosure).
Zone logic of the independent zones Z1 up to Z6
As was mentioned in the description of the measuring methods, each distance zone generates an output signal
which is associated with the zone and the affected phase. The zone logic combines these zone fault detections
with possible further internal and external signals. The delay times for the distance zones can be started either
all together on general fault detection by the distance protection function, or individually at the moment the fault
enters the respective distance zone. Parameter
Start Timers
(address
1510
) is set by default to
on Dis.
Pickup
. This setting ensures that all delay times continue to run together even if the type of fault or the select-
ed measuring loop changes, e.g. because an intermediate infeed is switched off. It is also the preferred setting
if other distance protection relays in the power system are working with this start timing. Where grading of the
delay times is especially important, for instance if the fault location shifts from zone Z3 to zone Z2, the setting
on Zone Pickup
should be chosen. The simplified zone logic is shown in Figure 2-71 for zone 1, Figure 2-
72 for zone 2 and Figure 2-73 for zone 3. Zones Z4, Z5 and Z6 function according to Figure 2-74.
In the case of zones Z1, Z2 and Z1B single-pole tripping is possible for single-phase faults if the device version
includes the single-pole tripping option. Therefore the event output in these cases is provided for each pole.
Different trip delay times can be set for single-phase and multiple-phase faults in these zones. In further zones,
the tripping is always three-pole.
Note
The binary input
„>1p Trip Perm“
(No. 381) must be activated to enable single-pole tripping. The internal
automatic reclosure function may also grant the single-pole permission. The binary input is usually controlled
from an external automatic reclosure device.
The trip delay times of the zones can be bypassed. The grading times are started either via zone pickup or
general pickup of the distance protection function. The undelayed release results from the line energization
logic. This logic may be externally initiated via the circuit breaker close signal derived from the circuit breaker
control switch or from an internal line energization detection. Zones Z4, Z5 and Z6 may be blocked by external
criteria (no. 3617
„>BLOCK Z4-Trip“
, no. 3618
„>BLOCK Z5-Trip“
, no. 3621
„>BLOCK Z6-Trip“
).