Electronic Trip Unit (Etu) - Siemens SENTRON 3WL10 Manual

2.6.3

Electronic trip unit (ETU)

The circuit breaker provides two series of electronic trip units (ETUs): ETUs of the 3-series
and ETUs of the 6-series.
To ensure the protection function of the device during operation at any time, all ETUs are
powered via transformers in each of the main circuits.
The current sensor of the circuit breaker comprises an iron-core transformer for powering the
ETU and a Rogowski coil for sensing the current to be able to detect operating states and
fault conditions precisely in the operational current and overcurrent range. Each transformer
can be optimized accordingly for its specific task. Thanks to the high accuracy of current
measurement, the circuit breaker is suitable for power/energy measurement. In addition, fine
adjustment of ground fault current monitoring is possible.
Depending on the type, the electronic trip units provide the following protection functions:
● Overload protection LT (Long Time)
Adjustable in steps of 40% to 100% of the rated current I
● Short-time-delayed short-circuit protection ST (Short Time)
For time-selective response in case of a short-circuit
● Instantaneous short-circuit protection INST
● Protection against residual currents to ground GF (ground fault).
The electronic trip units of the 6-series also provide enhanced protection functions that can
protect against directional power flows and power system anomalies affecting the voltage
and frequency, and can provide additional information for energy management and
communication functions:
● Metering functions
● Directional and enhanced protection functions (differentiation of power flow direction and
detection of directional faults, e.g. in ring or meshed systems)
● Communication
● Flexible, local digital inputs and outputs, and an external function box
● Software commissioning support with powerconfig
● Testing and archiving with the TD410 or TD420 test devices and the
powerconfig / powerservice software
3VA27 molded case circuit breakers & 3WL10 air circuit breakers
Manual, 10/2018, L1V30499596002-01
Description
2.6 Possible uses and portfolio
of the circuit breaker.
n
25