Siemens siprotec 7SD5, Руководство пользователя, Страница: 208 / 698

2 Functions
208
7SD5 Manual
C53000-G1176-C169-1
current from the phase currents. Naturally in this case also all three phase currents
derived from a set of three star connected current transformers must be available and
connected to the device.
The zero sequence voltage is determined by its defining equation 3 U
0
= U
L1-E
+ U
L2-
E
+ U
L3-E
Depending on the application for the fourth voltage input U
4
of the device, the
zero sequence voltage can be measured or calculated. If the fourth voltage input is
connected to the open delta winding U
delta
of a voltage transformer set and if it is con-
figured accordingly (address
210 U4 transformer
=
Udelta transf.
, see
Section 2.1.2.1), this voltage is used with the factor
Uph / Udelta
(address
211
,
see Section 2.1.2.1). If not, the device calculates the zero-sequence voltage from the
phase voltages. Naturally, all three phase-to-earth voltages obtained from a set of
three star-connected voltage transformers must be available and connected to the
device.
Definite Time Very
High-set Current
Stage 3
I
0
>>>
The triple zero-sequence current 3 I
0
is passed through a numerical filter and then
compared with the set value
3I0>>>
. If this value is exceeded an alarm is issued.
After the corresponding delay time
T 3I0>>>
has expired, a trip command is issued
which is also alarmed. The reset threshold is approximately 95 % of the pickup thresh-
old.
Figure 2-88 shows the logic diagram of the 3 I
0
>>> stage. The function modules „di-
rection determination“, „permissive teleprotection“, „switch onto fault“, and „inrush sta-
bilization“ are common to all stages and described below. They may, however, affect
each stage individually. This is accomplished with the following setting parameters:
•
Op. mode 3I0>>>
, determines the operating direction of the stage:
Forward
,
Reverse
,
Non-Directional
or
Inactive
,
•
3I0>>> Telep/BI
determines whether a non-delayed trip with the teleprotection
scheme or via binary input 1310
„>EF InstTRIP“
is possible (
YES
) or not (
NO
),
•
3I0>>>SOTF-Trip
, determines whether during energization of the feeder onto a
fault tripping with this stage shall be non-delayed (
YES
) or not (
NO
) and
•
3I0>>>InrushBlk
which is used to switch the inrush stabilization (rush blocking)
on (
YES
) or off (
NO
).
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