Siemens SIPROTEC 4, User Manual

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Single-Phase Overcurrent Protection
The single-phase overcurrent protection evaluates the current that is measured by the sensitive
Ι
NS
- or the
normal
Ι
N
input. Which input is used depends on the device version according to the order number.
Applications
•
Plain ground fault protection at a power transformer
•
Sensitive tank leakage protection.
Description
The single-phase definite time overcurrent ground protection is illustrated by the tripping characteristic as
shown in
Figure 2-40 . The current to be measured is filtered by numerical algorithms. Because of the high
sensitivity a particularly narrow band filter is used. 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 violated. After expiry of the respective delay time
50 1Ph-1 DELAY
or
50 1Ph-2 DELAY
,
the trip command is issued. The two elements together form a two-stage protection. The dropout value is
approximately 95% of the pickup value for currents greater than I > 0.3 · INom.
The current filter is bypassed if currents are extremely high in order to achieve a short tripping time. This
occurs automatically as soon as the instantaneous value of the current exceeds the set value of the
50 1Ph-2
PICKUP
element by at least factor 2 · √2.
[ueb-einph-kennlinie-020926-rei, 1, en_US]
Figure 2-40 Two-stage characteristic of the single-phase time-overcurrent protection
The following figure shows the logic diagram of the single-phase overcurrent protection function.
2.5
2.5.1
Functions
2.5 Single-Phase Overcurrent Protection
SIPROTEC 4, 7SJ62/64, Manual 117
C53000-G1140-C207-8, Edition 08.2016