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Important functions/parameters for communications
Thanks to their modular
construction and numerous I/O
modules, WL Circuit Breakers
offer flexible system solutions.
These solutions include load
management, alarms and
additional tripping conditions
via the extended protective
functions. Although the
utilization of these functions is
also possible without the use of
communications, their benefits
can be fully utilized when used
in communication applications.
Load shedding and restore are explained in this graphic. It's based on the assumption
Figure
of a WL Circuit Breaker with an overload setpoint of 1000 A.
2-8
WL PROFIBUS Communication and Electronic Accessories • July 2004
Communication-capable Circuit Breakers
Load Management
A circuit breaker with ETU745 or
higher, offers two current setpoint
values for local load management,
the upper setpoint being that of
load shedding, the lower setpoint
being that of load restore.
Note: These setpoints will not effect
the circuit breaker tripping function.
If the current exceeds the set load
shedding value in one phase, a
load shedding warning will be
generated. A load restore will only
be generated when this value drops
below the setpoint in all three
phases. The warning messages
are directly displayed by the BDA.
However, they are also stored in the
event log where they are labeled
with a time stamp.
Note: The event log is only available
with the COM15.
WL Circuit Breaker
The respective process for the load
restore threshold is reversed if all
three phases fall short of the
setpoint, and a load shed warning
will be generated. If only one of the
three currents exceeds the setpoint,
a load restore event will not be
generated.
In order to avoid load shedding on
the basis of short-time current
peaks and valleys, they can be
delayed by a delay time t
which
x
can be set to between 1 s and 15 s.
The load management parameters
can be found in the parameter tree
of the BDA.
The load shedding/load restore
signals are available as outputs of
the digital output module, which
are provided with a rotary selection
switch.
Extended Protective Function
The extended protective function
of the metering modules adds
additional tripping functions. The
options listed in table 2-8 can be
used as additional monitoring
functions.
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