Functions
2.1 General
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
67
If, for example, two single-phase earth faults occur on different lines — these may also be parallel lines —
(Figure 2-5), the protection relays detect the fault type on all four line ends L1-L2-E, i.e. the pickup image cor-
responds to a two-phase earth fault. If single pole tripping and reclosure is employed, it is therefore desirable
that each line only trips and recloses single pole. This is possible with setting
1155
3pole coupling
=
with
TRIP
. Each of the four devices detects a single-pole internal fault and can thus trip single-pole.
Figure 2-5
Multiple fault on a double-circuit line
In some cases, however, three-pole tripping would be preferable for this fault scenario, for example in the event
that the double-circuit line is located in the vicinity of a large generator unit (Figure 2-6). This is because the
generator considers the two single-phase ground faults as one double-phase ground fault, with corresponding-
ly high dynamic load on the turbine shaft. With the setting
1155
3pole coupling
=
with PICKUP
, the two
lines are switched off three-pole, since each device picks up as with L1-L2-E, i.e. as with a multi-phase fault.
Figure 2-6
Multiple fault on a double-circuit line next to a generator
Address
1156
Trip2phFlt
determines that the short-circuit protection functions perform only a single-pole
trip in case of isolated two-phase faults (clear of ground), provided that single-pole tripping is possible and per-
mitted. This allows a single-pole reclose cycle for this kind of fault. You can specify whether the leading phase
(
1pole leading Ø
), or the lagging phase (
1pole lagging Ø
) is tripped. The parameter is only available
in versions with single-pole and three-pole tripping. This parameter can only be altered using DIGSI at
Addi-
tional Settings
. If this possibility is to be used, you have to bear in mind that the phase selection should be the
same throughout the entire network and that it must be the same at all ends of one line. More information on
the functions is also contained in Section 2.25.1 Pickup Logic of the Entire Device. The presetting
3pole
is
usually used.
Line Sections
The line section parameters
6001
S1: Line angle
to
6012
S1: angle K0
,
6021
S2: Line angle
to
6032
S2: angle K0
and
6041
S3: Line angle
to
6052
S3: angle K0
are reserved for the double-
ended fault locator. They are used for parameterization of a line with different sections (overhead line - cable
sections). See Section 2.21 for more details.