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Functions
2.8 Earth Fault Protection in Earthed Systems (optional)
The zero-sequence voltage is determined by its defining equation 3·U
quence voltage is measured or calculated depending on the application of the fourth voltage input U
device. If the fourth voltage input is connected to the open delta winding U
if it is configured accordingly (address 210 U4 transformer = Udelta transf., see Section 2.1.2.1), this
voltage is used considering 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 ob-
tained from a set of three star-connected voltage transformers must be available and connected to the device.
Definite time very high set current stage 3I
The triple zero-sequence current 3 I
3I0>>>. If this value is exceeded an alarm is issued. After the corresponding delay time T 3I0>>> has ex-
pired, a trip command is issued which is also alarmed. The reset threshold is approximately 95 % of the pickup
threshold.
Figure 2-104 shows the logic diagram of the 3I
missive teleprotection" and the generation of the signals „Line closure" and „EF Inrush" 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 switching onto a fault tripping shall be instantaneous (YES)
or not (NO) with this stage.
• 3I0>>>InrushBlk which is used to switch the inrush stabilization (rush blocking) on (YES) or off (NO).
218
>>>
0
is passed through a numerical filter and then compared with the set value
0
>>> stage. The function blocks „direction determination", „per-
0
= U
+ U
+ U
0
L1-E
L2-E
L3-E
of a voltage transformer set and
delta
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
. The zero-se-
of the
4
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