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8 Function of the String Current Monitoring
8
Function of the String Current Monitoring
8.1 Requirements for Activating the String Current Monitoring
☐ The DC power of the PV array exceeds 5 % of the AC nominal power of the Sunny Central.
Value
P
DC
P
AC, nom
☐ The string current mean value of the individual groups is equal/greater than 0.5 A.
Value
I
String
8.2 Functionality of the String Current Monitoring
The string current monitoring measures the string currents and compares them to a mean value. If a
string current exceeds or falls short of the mean value by the set tolerance, the Sunny Central Control
displays warning 380 "SMU". The information below describes how the mean value is established,
what intervals are used to transmit data, and how the string current monitoring is configured.
Polling intervals
The Sunny String-Monitor continually measures the string currents and saves them in cycles.
Sunny Central Control reads these values every 5 minutes.
Group strings
Individual strings can be grouped in up to 4 groups in Sunny Central Control. Sunny Central Control
creates mean values for the groups 1, 2, and 3. These mean values are then used as reference values
for string current monitoring. The strings that are not monitored are grouped in group 0.
Tripping Time
The tripping time is the time span between the occurrence of a fault and the fault indication. The
tripping time is set to 180 minutes as default. The tripping time can be set between 2 and
1 440 minutes for each group.
Tolerance
The tolerance indicates how much the string current may deviate from the mean value. When the string
current is outside the tolerance limits, Sunny Central Control detects the deviation. The tolerance can
be set between 10 % and 100 %.
48
SSM-TEN103132
P
> 0.05 P
DC
Description
PV generator output
AC nominal power of the Sunny Central
I
String
Description
String current of the individual groups
AC,Nom
≥ 0.5 A
SMA Solar Technology AG
Technical Description
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