String Current Monitoring Function
SMA
Technologie AG
Page 40
SSM-TEN072310
Technical Description
Based on the calculation in this example, a value of 20 % is calculated for the error
sum. In this manner, the current difference of 0.5 A, which equates to a deviation of 10
% of the mean value, is added to the total for each polling interval of 5 minutes, until
the error sum of 20 % is reached. In this example, the error sum is reached after two
polling intervals, i.e. 10 minutes, which is the triggering time, and thus a warning
message is displayed in the Sunny Central.
The submenu
"SMUs...Failure"
shows which Sunny String Monitors and which
measuring channels deviate excessively from the group mean value. Upon confirmation
at the SSC, the error sum is reset, and the warning disappears from the display.
If a string fails completely, the current difference in the above example is 4.5 A, which
equates to a deviation of 90 % from the mean value. If the settings in the above
example remain the same, i.e. tolerance at 10 % and triggering time at 10 minutes, the
error sum of 20 % is already reached after the first Sunny Central polling interval (5
minutes). The Sunny Central now displays the warning "SMU".
On the basis of this example and the calculation formula, the sensitivity of the string
current monitoring can now be set by using the two parameters triggering time and
tolerance.
If you have questions relating to the correct parameter settings for the Sunny String
Monitor, you can contact SMA directly on the Sunny Central Serviceline. The telephone
number can be found in section 14 of this user manual.
The adjustable parameters are described in the following sections.
Activate the submenu
"SMUs"
from the menu
"Device Set-up"
. All settings
regarding all of the connected SSM-Cs can be made here. The parameters concerning
string current monitoring can be set in the submenu
"SMU Parameters"
.
