Siemens siprotec SJ62, Руководство пользователя

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2 Functions
123
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
2.5 Single-Phase Overcurrent Protection
The single-phase overcurrent protection evaluates the current that is measured by the
sensitive
I
NS
- or the normal I
N
input. Which transformer is used depends on the device
version and the order number.
Applications • Plain ground fault protection at a power transformer;
• Sensitive tank leakage protection.
2.5.1 Functional Description
The single-phase time overcurrent function yields the tripping characteristic depicted
in Figure 2-35. Numerical algorithms filter the current to be detected. A particular
narrow-band filter is used due to the possible high sensitivity. The current pickup
thresholds and tripping times can be set. The detected current is compared to the
pickup value
50 1Ph-1 PICKUP
or
50 1Ph-2 PICKUP
and reported if this is violat-
ed. The trip command is generated after the associated delay time
50 1Ph-1 DELAY
or
50 1Ph-2 DELAY
has elapsed. The two elements together form a two-stage pro-
tection. The dropout value is roughly equal to 95% of the pickup value for currents
I
>
0.3 ·
I
Nom
.
The current filter is bypassed if currents are extremely high to achieve a short tripping
time. This will always happen automatically when the instantaneous current value
exceeds the setting value of the
50 1Ph-2 PICKUP
element by at least factor 2 ·
√
2.
Figure 2-35 Two-stage characteristic of the single-phase time-overcurrent protection