Siemens SENTRON 3WL10 - Page 59

protection parameters (setB) with an external command or input. It then replaces the default
parameter setA.
The command to switch over can be issued if the circumstances of the power system change,
for example, when an emergency generator kicks in with the resulting load currents or
protection requirements.
Note
The second parameter set exists for all protection functions and thus also for DAS mode that
provides reduced, alternative protection settings just for the instantaneous short circuit
protection (INST).
There are various ways of switching between parameter sets A and B:
• Locally, on the display of the ETU of the 6-series
• Via communication
• By input at the digital I/O module IOM040 or IOM300, which was triggered by an external
signal
• By input at the digital I/O module IOM040 or IOM300, which was triggered by an internal
signal, for example, the pre-alarm response thresholds (PAL)
• Automatically after a de󹪝ned delay time, after the circuit breaker has been closed.
Thermal memory
The electronic trip units have a thermal memory for the overload protection function (LT) to
protect equipment from overheating due to overload.
The thermal memory maps the circuit breaker's thermal state as determined by the load
current. It shortens the delay time of the protection function, considering the existing
thermal load of the circuit breaker. This can be the case after fast reclosure of the circuit
breaker following an overload trip. The size of the overcurrent that caused the trip and
therefore the amount of overheating is considered.
The thermal memory can be disabled on electronic trip units of the 6-series. The thermal
memory should remain activated in normal operation. It is the responsibility of the
commissioning engineer/company operating the installation to provide additional thermal
overload protection for the downstream power distribution system while the thermal
memory is deactivated.
Enhanced protection functions expanded with the MFAdvanced metering module for ETUs of
the 6‑series.
The protection functionalities of the ETUs of the 6‑series can be enhanced if the ETU is expanded
with the MFAdvanced metering function. In this way, complex protection functions can be
generated based on simultaneous processing of current and voltage signals and the circuit
breaker becomes a central control and protection element in the installation.
The enhanced protection functions can be set to the operating modes: "closed", "only alarm"
or "open".
Description
2.9Electronic trip unit ETU
3VA27 molded case circuit breakers & 3WL10 air circuit breakers
58 Equipment Manual, 10/2023, L1V30499596002-03