SMA SSM8-21-BS - Manual (Page 13)

SMA Solar Technology AG 4 Product Description
Installation Manual SSMxx-21-IA-BS-JP-en-20 13
The individual error sums of the measuring channels are reset at midnight.
Query Intervals
The Sunny String-Monitor continuously measures the string currents and performs cyclic storage of the measured values.
The data logger reads out these values every five minutes.
Tripping Time
The tripping time is the time span between the occurrence of an error and the error message. The tripping time is set to
180 minutes by default. You can set the parameter for the tripping time to between 2 minutes and 1,440 minutes.
Tolerance
The tolerance indicates how much the string current is allowed to deviate from the mean value. If the string current is
outside the tolerance limits, the data logger detects the deviation and stores it. The tolerance can be set between 10%
and 100%.
Grouping the Strings
To simplify monitoring, you can assign the strings to the eight measuring channels. Should individual strings be shaded,
aligned differently or fitted with different PV modules, it is also possible to group the individual measuring channels. This
makes it possible to compare measuring channels with the same properties.
Comparison
Every five minutes, the data logger compares the string current with the mean value for the group. If the string current
exceeds the tolerance limit, the data logger records the deviation. If at the next query, there is still a deviation between
the string current and the mean value, the deviations are added together. If the sum of the deviations exceeds the error
sum, the data logger issues the warning 380 SMU. When the error is acknowledged, the error sum is reset and the
warning disappears from the display.
It is possible to see which Sunny String-Monitor and which measuring channels deviate from the mean value of the group
via the Sunny Central Control or via the SC-COM.
All string currents are compared with this mean value at the five-minute query interval. If all the string currents are within
the set tolerance of 10%, no addition is carried out.
However, if one string has a string current of 6 A, the difference between the actual string current of 6 A and the tolerance
limit of 5.5 A is added. The difference is 0.5 A which is a deviation of 10% from the mean value. This difference of 10%
is now added to the total until the error sum of 20% is reached.
The error sum is reached when the error remains the same for two query intervals. The data logger issues the warning
380 SMU.
Example:
It is assumed that at time t
0
the mean value of a group is 5 A. The set tolerance is 10%. This means that the tolerance
range is from 4.5 A to 5.5 A. The tripping time is set to 10 minutes. The query interval is five minutes. The error sum can
therefore be calculated as follows: