SMA America, LLC
Safety
Installation Guide
SB20_25_30HFUS-eng-IUS113711
13
Principle of a PV plant with this Sunny Boy
You must operate the Sunny Boy only with PV arrays (modules and cabling) of protection class II.
Do not connect any sources of energy other than PV modules to the Sunny Boy.
When designing the PV system, ensure that the values comply with the permitted operating range of
all components at all times. The free design program ”Sunny Design” (www.SMA‑America.com) will
assist you. The manufacturer of the PV modules must have approved the modules for use with this
Sunny Boy device. You must also ensure that all measures recommended by the module manufacturer
for long-term maintenance of the module properties are taken. You will find further information in the
download area of www.SMA‑America.com.
Do not use the Sunny Boy for purposes other than those described here. Alternative uses,
modifications to the Sunny Boy or the installation of components not expressly recommended or sold
by the manufacturer void the warranty claims and operation permission.
Anti-Islanding protection
Islanding is a condition that can occur if the power distribution grid is disconnected while the
Sunny Boy is operating and the remaining load is resonant at 60 Hz and matches the output of the
Sunny Boy perfectly. This condition is highly unlikely and had never been witnessed outside of a
controlled laboratory. Nevertheless, the Sunny Boy incorporates an advanced active islanding
protection algorithm to ensure that the system will not export power into a balanced 60 Hz resonant
load while the utility is disconnected. The Sunny Boy periodically injects both leading and lagging
reactive current into the power distribution grid. This method has been proven by Underwriters
Laboratories to effectively destabilize and disconnect from a balanced island condition.
Position
Name
A
PV array
B
Sunny Boy with integrated SMA DC-Disconnect
C
Line circuit breaker
D
Load
E
Energy meter
F
Power distribution grid
