SMA SI 3324 Installation - Manual (Page 35)

SMA Technologie AG Electrical Connection
Installation Guide SI3324/4248-14:SE2406 Page 35
Calculating the Required Grounding Conductor Cross-section
SMA Technologie AG cannot calculate generally valid values for the required cross-
section of the grounding conductor for external grounding of the negative pole of the
batteries. The conductor dimensions depend on the type of batteries connected, the
external fuse (DC side) and the material used in the the grounding conductor.
However, the cross-section can be easily calculated using a formula.
The required cross-section of a (copper) grounding conductor can be calculated
using the following formula. Trigger times, e.g. for the integrated DC circuit breaker,
of about 25 ms are typical for short circuit currents between 2000 A and 10,000 A.
A grounding conductor of 16 mm² cross-section is thus adequate for short circuit
currents up to 10,000 A.
Exact calculation of the grounding conductor cross-section must take account
of the regionally applicable standards and guidelines (e.g DIN VDE 0100 Part
540).
t = Trigger time in seconds (s)
I
SC
= Maximum battery current (short circuit current) in
amperes (A)
S = Conductor cross-section in square millimeters (mm²)