Siemens siprotec 7SD5, Руководство пользователя

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2 Functions
128
7SD5 Manual
C53000-G1176-C169-1
the zero-sequence voltage (address
1505 3U0> COMP/ISOL.
). Please note that
triple zero-sequence voltage 3U
0
is relevant here. With a full displacement its value
will be
√
3 times the phase-to-phase voltage. Afterwards the delay
T3I0 1PHAS
is not
active anymore: an earth fault occurring now in a different phase can only be a double
earth fault.
Switching onto a
Fault To determine the reaction of the distance protection during closure of the circuit
breaker onto a dead fault, the parameter in address
1532 SOTF zone
is used. The
setting
Inactive
specifies that there is no special reaction, i.e. all distance stages
operate according to their set zone parameters. The setting
Zone Z1B
causes all
faults inside the overreaching zone Z1B (in the direction specified for these zones) to
be cleared without delay following closure of the circuit breaker. If
Z1B undirect.
is set, the zone Z1B is relevant, but it acts in both directions, regardless of the operat-
ing direction set in address
1651
or
1751 Op. mode Z1B
. The setting
PICKUP
implies that the non-delayed tripping following line energization is activated for all rec-
ognized faults in any zone (i.e. with general fault detection of the distance protection).
Blocking of Zone Z1 When the differential protection is active, zone Z1 can be blocked by setting
1533 Z1
blkd by diff
to
YES
; this means that there will be no measurement and no pickup
in Z1 as long as the differential protection is effective (No. 3120
„Diff active“
).
Zone Z1 will be reactivated immediately when the differential protection is ineffective,
e.g. due to a communication failure. With address
1533 Z1 blkd by diff
set to
NO
, zone Z1 operates independently of the differential protection.
Zone Z1 can also be blocked by the binary input 3610
„>BLOCK Z1-Trip“
. This
binary input allows, for instance, to specify further blocking conditions relating to the
interaction with the differential protection using CFC. The effect of the binary input
does not depend on the status of the differential protection.
Load Range (only
for Impedance
Pickup) When using the impedance pickup function, or with the variants 7SD5***-*****-* E **
and 7SD5***-*****-* H *, there may be a risk of encroachment of the load impedance
into the tripping characteristic of the distance protection on long heavily loaded lines.
To exclude the risk of unwanted fault detection by the distance protection during heavy
load flow, a load trapezoid characteristic may be set for tripping characteristics with
large R-reaches, which excludes such unwanted fault detection by overload. This load
trapezoid does not apply for the other pickup modes since the trip polygons are only
released after pickup and the pickup function fulfills the task of distinguishing clearly
between load operation and short-circuit. This load area is considered in the descrip-
tion of the tripping characteristics (see also Sections 2.5.2 and 2.5.3).
The R-value
R load (Ø-E)
(address
1541
) refers to the phase-earth loops,
R load
(Ø-Ø)
(address
1543
) to the phase-phase loops. The values are set somewhat (ap-
prox. 10 %) below the minimum expected load impedance. The minimum load imped-
ance results when the maximum load current and minimum operating voltage exist.
Calculation Example:
110 kV overhead line 150 mm
2
with the following data:
maximum transmittable power
P
max
= 100 MVA corresponds to
I
max
= 525 A
minimum operating voltage
U
min
= 0,9 U
N
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