3WL Air Circuit Breakers
3WL Air Circuit Breakers/Non-Automatic Air Circuit Breakers up to 6300 A (AC)
General data
14
Siemens · 2012
Electronic releases (ETU)
The electronic release is controlled by a microprocessor and op-
erates independently of an auxiliary voltage. It enables systems
to be adapted to the different protection requirements of distri-
bution systems, motors, transformers and generators.
Communication capability
The international standard PROFIBUS DP or MODBUS can be
used to transmit data such as current values, switching states,
reasons for tripping etc. to central computers.
Data acquisition and energy management are possible in con-
junction with the
Plus
measurement function.
A new internal circuit breaker data bus allows switchboard panel
communication between the circuit breaker and secondary de-
vices in the circuit breaker section:
• Actuation of analog displays
• Facility to test the communication build-up with circuit break-
ers
• Display of tripping state and tripping reasons
• Input module for reading in further switchgear panel signals
and for transmission of these signals to the PROFIBUS DP or
MODBUS
• Various output modules for displaying measured values.
This means that it is not only possible to monitor the device re-
motely, but also to transmit current values from the entire system
and perform switching operations remotely.
I
2
t and I
4
t characteristic curve for overload protection
The best protection for the whole switchgear is achieved by set-
ting the tripping characteristic curve to an optimum value. In or-
der to achieve optimal discrimination for upstream fuses or me-
dium voltage protection systems, the inclination of the
characteristic curve can be selected for the overload range.
The overload protection L (long time protection) for the elec-
tronic releases ETU45B and ETU76B allows the characteristic
curve to be switched between
I
2
t
and
I
4
t
.
The
I
4
t
characteristic improves discrimination for downstream
circuit breakers and fuses.
Electronic releases ETU
Modularity has also been strictly emphasized during the devel-
opment of the electronic releases. These are some of the mod-
ules which can be easily retrofitted at any time:
• Ground-fault protection module
• Communication
• Measurement function
•Display
• Rated current module (Rating Plug)
This allows quick adaptation to new local mains specifications.
In addition, innovative functions have been included in the ETUs.
Rated current module/Rating Plug
The rated current module is an exchangeable module which al-
lows the user to reduce the rated device current so as to adapt
it optimally to the plant; e.g.if a new plant section is taken into op-
eration. The rated current module must be selected to fit the
rated current of the plant.
Example of configuration for ETU45B
Measurement function Plus
Selectable parameters
In the case of quick changes of power supply conditions,
e. g. for switchovers from transformer to generator operation or
if a section of the supply is disconnected when the shift
changes, the 3WL circuit breaker allows the relevant protection
parameters to be quickly adapted to the new conditions.
The ETU76B contains two independent tripping characteristic
curves (parameter sets). The switchover is completed within
200 ms and is performed with the help of an external signal.
Ground-fault
protection
module (retro-
fittable)
Tripped indicator/
Reset button
LCD alpha-
numeric
with 15°
inclination
and rotatable
through 180°
Slide switch
for switchable
overload
characteristic
curve
Rated current
module/
rating plug
© Siemens AG 2011
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