Siemens siprotec 7SD5 User Manual page 208

2 Functions
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
E
zero sequence voltage can be measured or calculated. If the fourth voltage input is
connected to the open delta winding U
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 The triple zero-sequence current 3 I
compared with the set value 3I0>>>. If this value is exceeded an alarm is issued.
High-set Current
Stage 3I >>> After the corresponding delay time T 3I0>>> has expired, a trip command is issued
0
which is also alarmed. The reset threshold is approximately 95 % of the pickup thresh-
old.
Figure 2-88 shows the logic diagram of the 3I
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,
• 3I0>>> Telep/BI determines whether a non-delayed trip with the teleprotection
• 3I0>>>SOTF-Trip, determines whether during energization of the feeder onto a
• 3I0>>>InrushBlk which is used to switch the inrush stabilization (rush blocking)
208
+ U Depending on the application for the fourth voltage input U
L3-E
Reverse, Non-Directional or Inactive,
scheme or via binary input 1310 „>EF InstTRIP" is possible (YES) or not (NO),
fault tripping with this stage shall be non-delayed (YES) or not (NO) and
on (YES) or off (NO).
of a voltage transformer set and if it is con-
delta
is passed through a numerical filter and then
0
>>> stage. The function modules „di-
0
= U + U
0 L1-E L2-
of the device, the
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7SD5 Manual
C53000-G1176-C169-1