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Figure 2-88
Logic diagram of the 3I
Definite Time High-
The logic of the high-set current stage 3I
In all references 3I0>>> must merely be replaced with 3I0>>. In all other respects
set Current Stage
3I
>>
Figure 2-88 applies.
0
Definite Time Over-
The logic of the high set current stage 3I
stage. In all references 3I0>>> must merely be replaced with 3I0>. In all other re-
current Stage 3I
>
0
spects Figure 2-88 applies. This stage operates with a specially optimized digital filter
that completely suppresses all harmonic components beginning with the 2nd harmon-
ic. Therefore it is particularly suited for a highly-sensitive earth fault detection.
A fourth, definite time stage can be implemented by setting the „inverse-time" stage
(refer to the next paragraph) to a definite-time stage.
Inverse Time Over-
The logic of the stages with inverse time delay functions in the same way as the re-
current Stage 3I
maining stages. This stage operates with a specially optimized digital filter that com-
0P
pletely suppresses all harmonic components beginning with the 2nd harmonic. There-
fore it is particularly suited for a highly-sensitive earth fault detection. However, the
time delay is calculated here based on the type of the set characteristic, the intensity
7SD5 Manual
C53000-G1176-C169-1
2.8 Earth Fault Protection in Earthed Systems (optional)
>>> stage
0
>> is the same as that of the 3I
0
>, too, is the same as that of the 3I
0
>>> stage.
0
>>>
0
209
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