SMA S Technical Description page 158

Troubleshooting/Problem Solving SMA Solar Technology AG
Why do I need the PEN conductor to be grounded upstream of the Sunny Backup system,
yet still within the system? The PEN conductor is already grounded in the local grid!
In the event of a deliberate grid shutdown on the part of your distribution grid operator (e.g. for
maintenance work), the PEN conductor can be interrupted if the corresponding phase conductors are
disconnected. The Sunny Backup system then lacks a ground connection, which is unacceptable, both
in terms of functionality and safety. Furthermore, an increase of the PEN conductor's voltage in the
grid is prevented in stand-alone operation.
At our site, there is only a TT grid, and my distribution grid operator does not allow the N
conductor to be grounded. Can I operate the Sunny Backup system anyway, without
grounding the N conductor?
NO, in this form, the system is only certified for TN systems. Consult your energy supply company to
ascertain the conditions under which installation is permissible.
Why must I set the Sunny Boy to use "stand-alone grid parameters"? It has operated
without problems up to now!
As long as your system is operating on the public grid, the high power output from connected power
stations means that the public grid can ensure that voltage and frequency do not change if you
connect loads to the grid. In a small stand-alone grid, in which the consumer power is about the same
as the installed capacity of the Sunny Backup 2200, such effective adjustment is not possible.
Therefore, frequency and voltage are not as constant as in the so-called "rigid grid", so the Sunny Boys
in stand-alone grid operation would often interpret these deviations as grid faults and deactivate. To
enable practical utilization of the PV system in the event of grid failure, it must also be able to operate
in a "soft" grid. This is made possible by means of switching to the so-called "stand-alone grid
parameters".
But the Sunny Boy also feeds into the grid. Is that permissible with the "grid parameters"
deactivated?
This is permissible for the Sunny Boy or any other PV inverter, but only in conjunction with the upstream
Sunny Backup system or an automatic disconnection device certified according to the applicable
standard in the installation country (for Germany: ). The Sunny Boy may not operate directly on the
grid in this manner, because it must adhere to the parameters (voltage and frequency limits) specified
in the standard applicable in the installation country and must also contain the automatic
disconnection device specified by that standard. The Sunny Boy meets both these requirements with
its integrated "SMA grid guard version 2". Only once the Sunny Boy is connected to the Sunny
Backup system's X2 / PV System input, may "SMA grid guard version 2" be deactivated. Its functions
are then assumed by the control and monitoring within the Sunny Backup System S.
What can I do if the QCG suddenly does not run?
Switch off the Sunny Backup 2200 (section 11.3 „Deactivation" (95)) and switch it back on (section
11.1 „Activation / Startup" (91)).
158 SBU2200-TEN083320 Technical Description