Application - ABB REB670 Applications Manual

Section 12
Control
12.2.2
314

Application

In certain countries it is standard practice to provide delayed restoration after busbar
protection operation for internal fault, reason being that many busbar faults are of the
transient natures that is, animals, birds, storm, flying objects, etc. In such applications,
typically one pre-selected feeder is automatically closed with certain time delay in
order to try to re-energize the faulty bus. Typically, the longest overhead line is
selected in order to limit the fault current in case of permanent busbar fault. If the first
feeder is successfully closed, all other feeder which have been connected to the same
busbar, are automatically put back into service.
Sensitive differential protection level available in REB670 can be used during such
operation, if increased sensitivity from busbar protection is required. Such busbar
restoration logic can be implemented by using optionally available auto reclosers and
built-in logical gates. Two auto reclosers are available.
Automatic reclosing is a well-established method for the restoration of service in a
power system after a transient line fault. The majority of line faults are flashovers,
which are transient by nature. When the power line is switched off by the operation of
line protection and line breakers, the arc de-ionizes and recovers its ability to withstand
voltage at a somewhat variable rate. Thus, a certain dead time with a de-energized line
is necessary. Line service can then be resumed by automatic reclosing of the line
breakers. The dead time selected should be long enough to ensure a high probability of
arc de-ionization and successful reclosing.
For individual line breakers, auto reclosing equipment, the required circuit breaker
dead time is used to determine the "dead time" setting value. When simultaneous
tripping and reclosing at the two line ends occurs, line dead time is approximately
equal to the auto recloser "dead time". If the auto reclosing dead time and line "dead
time" differ then, the line will be energized until the breakers at both ends have opened.
1MRK 505 370-UUS A
M12391-3 v8
Busbar protection REB670 2.2 ANSI
Application manual