SMA SI 3324 Errata - Manual (Page 5)

SMA Solar Technology AG Electrical Connection
Installation Guide 5/16 SI3324_4248-E-IEN094410
SMA Solar Technology offers the following external DC fuses:
1.3.2 Grounding
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 cable.
The required cross-section of a (copper) grounding cable 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 cable of 16 mm² cross-section is thus adequate for short-circuit currents up to 10,000 A.
BATFUSE-B.01-2 Battery connection box for a Sunny Island 4248 with fuse switch
disconnector (NH01 200 A)
BATFUSE-B.01-3 Battery connection box for a Sunny Island 3324 with fuse switch
disconnector (NH01 250 A)
DC cables
The DC cables should be as short as possible (always < 30 m). Since high currents flow
through the battery cables, they can become very warm. Long cables and insufficient cable
cross-sections reduce the system efficiency as well as the overload capabilities.
• Do not lay the battery cable under plaster or in armored plastic pipes.
• Use both DC negative and both DC positive connection terminals for the DC
connection.
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, it must be established separately by an installer
outside of the Sunny Island.
• When grounding the battery, the Sunny Island's enclosure must be additionally
grounded, also in the DC area.
Determining the cross-section
Exact calculation of the grounding cable 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 A
S = cable cross-section in mm
2