9.4.2
Function block
Figure 534: Function block
9.4.3
Functionality
About 80 to 85 percent of faults in the MV overhead lines are transient and
automatically cleared with a momentary de-energization of the line. The rest of the
faults, 15 to 20 percent, can be cleared by longer interruptions. The de-energization
of the fault location for a selected time period is implemented through automatic
reclosing, during which most of the faults can be cleared.
In case of a permanent fault, the automatic reclosing is followed by final tripping.
A permanent fault must be located and cleared before the fault location can be
re-energized.
The autoreclosing function DARREC can be used with any circuit breaker suitable for
autoreclosing. The function provides five programmable autoreclosing shots which
can perform one to five successive autoreclosings of desired type and duration, for
instance one high-speed and one delayed autoreclosing.
When the reclosing is initiated with starting of the protection function, the
autoreclosing function can execute the final trip of the circuit breaker in a short
operate time, provided that the fault still persists when the last selected reclosing
has been carried out.
9.4.3.1
Protection signal definition
The
Control line setting defines which of the initiation signals are protection start
and trip signals and which are not. With this setting, the user can distinguish the
blocking signals from the protection signals. The
Control line setting is a bit mask,
that is, the lowest bit controls the
INIT_1
line and the highest bit the
INIT_6
line.
Some example combinations of the
Control line setting are as follows:
Control functions
1MRS757644 H
1012
620 series
Technical Manual
