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5 Electrical Connection
5.8.2 Dimension the Connection Cable for the Undervoltage
Release
Depending on the order, the Sunny String-Monitor includes a DC circuit breaker with a remote trigger.
In this case, the DC circuit breaker is equipped with a shunt release. Depending on the order, the
Sunny String-Monitor includes as a shunt release an operating current release or an undervoltage
release.
By means of the shunt release it is possible to disconnect the PV array from the inverter through the
DC switch.
The undervoltage release is used to switch off the DC switch in an electrically-controlled fashion. The
DC switch is triggered when there is no voltage at the undervoltage release, or if the voltage falls
below 85 % of the release nominal voltage U
again after the voltage rises above 85 % of the undervoltage release nominal voltage U
switch can be switched on manually only if there is voltage at the undervoltage release. In order to
avoid an inadvertent tripping, an uninterrupted power supply is recommended. The undervoltage
release is designed for continual operation. Activation takes place via a normally break contact. The
undervoltage release is the suitable tripping element for secure shutdowns or locks, for example, an
emergency stop, because there is always a disconnection if there is a fault. The minimum interruption
time for secure tripping of the undervoltage release is 1 second.
☐ Cable cross section: at least 2.5 mm
☐ Total cable length: 1 000 m maximum.
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SSM-TEN103132
. After tripping, the circuit breaker can be connected
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2
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SMA Solar Technology AG
. The DC
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Technical Description
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