SMA SI 3.0-11 Quick Reference Guide V.3.0 - Manual (Page 17)

SMA Solar Technology AG 3 Information and System Description
Installation - Quick Reference Guide Ersatzstrom-IS-en-30 17
An automatic transfer switch provides the following functions:
• Grid disconnection isolates the battery backup grid from the utility grid.
• The grounding device grounds the battery backup grid after it has been disconnected from the utility grid.
The grounding device is only required in systems with all-pole disconnection.
• The phase coupling connects the line conductors of the battery backup system to a single-phase distribution grid.
The phase coupling is a function for single-phase battery backup systems if the installation of the battery backup grid
is three-phase.
• The SMA Energy Meter measures the grid feed-in and the purchased electricity.
The SMA Energy Meter is only required in systems for increased self-consumption.
3.4.2 Grid Disconnection
Within the automatic transfer switch, a tie switch disconnects the battery backup grid from the utility grid. The conditions
at the tie switch differ depending on the installation site. SMA Solar Technology AG offers two basic structures for grid
disconnection and these differ as far as the tie switch is concerned:
• Grid disconnection with all-pole disconnection of the battery backup grid from the utility grid
In the event of grid failure, a tie switch disconnects all line conductors and the neutral conductor from the utility grid.
If the technical connection requirements of the grid operator or the local standards and directives call for or allow
all-pole disconnection, you must install this basic structure. You must install all-pole disconnection in the following
countries:
– Belgium
– Denmark
– Germany
– France
– Austria
– Switzerland
• Grid disconnection without all-pole disconnection of the battery backup grid from the utility grid
In the event of grid failure, a tie switch disconnects all line conductors from the utility grid. The neutral conductor of
the battery backup grid remains permanently connected to the utility grid. If the technical connection requirements
of the grid operator or the local standards and directives prohibit disconnection of the neutral conductor, you must
install this basic structure. In Australia, you must install a battery backup system without all-pole disconnection.
Independent of the basic structure, you must adjust the ampacity of the tie switch in accordance with the requirements on
site. The tie switch must be designed for at least the operating range of the upstream fuse or the maximum short-circuit
current of the PV system.
The circuitry of the automatic transfer switch is designed in such a way that the tie switch disconnects only in the event of
a grid failure. If you stop or switch off the Sunny Island, the battery backup grid remains connected to the utility grid.
This means that you can carry out maintenance work on the battery without the supply to the loads being interrupted.