SMA SI 5048, Technical Description

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Electrical Connection SMA Solar Technology AG
30 SI5048-TEN093630 Technical Description
6.1 Connection to ground
Before commissioning the Sunny Island it must be externally grounded according to the relevant
regulations. To allow different types of grounding, the N connection of the Sunny Island is
not
connected to PE at the factory. However, since a connection between N and PE is required for correct
operation, this must be done outside of the device.
Due to filter measures in the device, increased leakage currents against PE can always occur. For this
reason, a "fixed connection" of ground must be implemented according to EN 50178. Ground the
Sunny Island with a copper conductor (at least 10 mm² cross-section), or with two separate copper
conductors with a cross-section of at least 4 mm² each.
Calculating the Required Grounding Cable Cross-Section
SMA Solar Technology cannot state generally valid values for the cross-section of the cable required
for the external grounding of the battery. The cable dimensions depend on the type and size of the
battery connected, the external fuse (DC side) and the material used in the grounding conductor.
The required cross-section of a (copper) grounding conductor can be calculated using the following
formula. Trigger times for short-circuit currents of between 2,000 A and 10,000 A are typically
about 25 ms.
A grounding conductor of 16 mm² cross-section is thus adequate for short-circuit currents up to
10,000 A.
Wiring of the (Protective) Ground
In stand-alone configurations, the (protective) ground of the Sunny Island and its individual
components must be wired as a TN grid only. Be sure to observe all applicable regional
standards and guidelines.
External grounding
External grounding of the negative pole of the batteries is possible, because the batteries
and the grid side are galvanically isolated within the Sunny Island. In this case make sure
that the high currents that may occur under fault conditions can be adequately discharged.
If a ground connection is necessary, establish it separately outside of the Sunny Island.
Determining the cross-section
Exact calculation of the grounding conductor cross-section must take account of the
regionally applicable standards and guidelines.
t = interruption time in seconds
I
SC
= Maximum battery current (short-circuit current) in
amperes
S = conductor cross-section in mm²