SMA
Solar Technology AG
Additional Functions
Technical Description
SI2012_2224-TEN082311
117
11 Additional Functions
11.1 Load shedding
The Sunny Island can automatically switch off loads to protect the batteries from deep discharge.
To do this, an external (AC or DC) power contactor must be installed between the Sunny Island and
the loads (see also chapter 19.3 "Accessories (Optional)" (Page 195)).
The graphic shows an example for the settings that minimize the load shedding function at night.
From 6:00 a.m. to 22:00 p.m. the load shedding is activated for a charge state (SOC) of 40 %,
during nighttime (from 22:00 p.m. to 6:00 a.m.), by contrast, the charge state of the battery is
allowed to go down to 30 % before the load shedding is activated.
The load shedding function can be assigned twice. In the parameters mentioned above, the "Lod1"
part represents the first assigned function and the "Lod2" part represents a second, identical
function. These two load shedding functions, which are dependent on the battery's state of charge,
allow for tiered load-shedding in which, by using different SOC values, different priorities can be
given to various load groups.
NOTICE!
Faulty system operation due to lack of load shedding.
Install external load-shedding protection in case the island grid system on the AC-
generating side is coupled to PV generators or wind generators.
If there is overloading due to low energy production or very high energy consumption,
you must be able to switch off loads.
Always switch off the loads, never the energy producers (e.g., Sunny Boy)!
