SIPROTEC 7SS52 V4 is used for busbar and breaker failure
protection. It is a selective, reliable and fast protection for busbar
short-cirtues and circuit breaker failures in medium voltage, high voltage, and
extra high voltage sub-stations. It is suitable for almost all busbar
configurations. In the bay units the feeder or coupler currents are measured by
time-synchronized, digitalized, and transmitted to the central unit via fast
serial port. The input current is depending on the main CT design. It can be
used with all types of switchgear with either conventional or linearized CT.
It is consist of compact bay units which are connected with the central unit by fiber-optic cables. All
are processed in a digital manner. Bay units capture the isolator position and
bay-related binary signals, process functions of the breaker failure protection
and fulfil auto diagnostics tasks. Central units is measured current from the
protection function and transmit the result in bay units, which perform logical
combination of the results.
So, question is how to protect the busbar by SIPROTEC 7SS52:
Here is some very basic general function:
·
Blocking the bus section in case of isolator
fault, bay fault, and value error.
·
Evaluation of the differential current in
conjunction with current stabilization
·
Short circuit between CT & CB of a line by
end fault protection.
·
Fast tripping up to 15ms
·
Bus selective zone normal and earth fault pick
up characteristics.
·
Compare CT ratio
Now we see how to protect breaker failure protection by
SIPROTEC 7SS52:
·
In case of busbar short circuit, a breaker
failure is detected by comparison of current thresholds.
·
If CBF occur, a bay unit trip the CB at remote
end.
·
Reduced response time in case of CB malfunction.
·
External breaker failure can be started for
single or three phases.
·
CB fail detect for breaker failure protection.
