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Description
2.7 Possible uses and portfolio
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
2.7.4
3VA27 / 3WL10 for motor protection applications
Both the current-carrying 3WL10 and the current-limiting 3VA27 are suitable and can be used
for motor protection.
First of all, the usability of both device classes is verified by checking the maximum short-
circuit power of the transformer / generator.
The following must be considered: In the 3VA27, the molded case circuit breaker reduces
the let-through currents above approx. 32 kA in case of a short-circuit, i.e. the load reaching
downstream equipment, e.g. contactor and motor, is lowered (less thermal load, lower
dynamic forces).
However, the 3VA27 also trips instantaneously above the max. I
The 3WL10, however, is designed to prevent automatic lifting of the contacts above the max.
I
to avoid unwanted tripping of the device.
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26
of the circuit breaker.
n
(15xI
i
3VA27 molded case circuit breakers & 3WL10 air circuit breakers
Equipment Manual, 10/2023, L1V30499596002-03
).
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