Introduction
6
7SS52 V4 Manual
C53000-G1176-C182-3
• Output of indications to
− Control center
− LEDs
− Binary outputs of the central unit
• Commissioning support by measuring and display functions, and output of indica-
tions to a control center as well as to LEDs and outputs of the central unit.
Busbar
protection
The digital busbar protection contains the following functions:
• Evaluation of the differential current in conjunction with through-current stabilization
(Figure 1-2, page 7)
• Trip decision based on 3 independent measurements. 2 measurements are based
on busbar configuration, and the third measurement considers all busbar sections
independent of the isolator replica (check zone).
• Fast tripping (typical trip time 15 ms)
• Busbar protection with up to 12 bus zones (BZ), 12 bus coupler (auxiliary bus) sec-
tions (AB) and up to 48 bay units
• Protection of systems with up to quintuple busbars (including transfer busbars)
• Stabilization against spurious tripping in case of external faults and CT saturation
• Zone-selective and phase-selective blocking of the busbar protection by the differ-
ential current monitor
• Selective blocking of the bus section in case of
− Isolator faults
− Bay faults (bay unit, FO cable)
− Measured value error
− Response of the zero crossing supervision
• Characteristics for check zone and bus-selective zones can be set independently
from each other
− Normal pick-up characteristic (Figure 1-2, page 7)
− Earth fault characteristic (Figure 1-3, page 7)
• Matching to different CT ratios without interposing matching transformers
• Selective clearance of short-circuits even on the bypass bus with signal transmis-
sion to the remote end
• Detection and disconnection of short-circuits in the coupler bay between current
transformers and circuit-breaker based on current measurement and selective un-
balance
• Detection and disconnection of short-circuits between current transformers and cir-
cuit-breaker of a line by end fault protection
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