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Photovoltaic application example
Superior surge protection from Weidmüller
Our surge protection modules in Class I and Class II (B and C
arresters) ensure voltage occurrences are quickly limited and
that the current is safety discharged. This allows you to avoid
expensive damages or the potential for complete power
failure in your photovoltaic facility.
For buildings with or without lighting protection systems
– we have the right product for every application! We can
deliver the modules as you require – fully customised and
pre-wired into housings.
Deploying surge protection devices (SPDs) in
photovoltaic systems
Photovoltaic energy is a vital component of the overall
energy production from renewable energy sources.
There are a number of special characteristics that need to
be considered when deploying surge protection devices
(SPDs) in photovoltaic systems. Photovoltaic systems have a
DC voltage source, with specic characteristics. The system
concept must therefore take these specic characteristics
into consideration and co-ordinate the use of SPDs
accordingly. For instance SPD specications for PV systems
must be designed both for a maximum no-load voltage of
the solar generator (VOC STC = voltage of the unloaded
circuit under standard test conditions) as well as with regard
to ensuring maximum system availability and safety.
External lightning protection
Owing to their large surface area and generally exposed
installation location, photovoltaic systems are particularly
risk from atmospheric discharges – such as lightning. At
this point there is a need to differentiate between the effects
of direct lightning strikes and so-called indirect (inductive
and capacitive) strikes. On the one hand the necessity for
lightning protection depends on the normative specications
of the relevant standards and on the one hand, the
necessity for lightning protection spends on the normative
specications of the relevant standards. On the other hand, it
depends on the application itself, in other words, depending
on if it is a building or a eld installation. With building
installations a difference is drawn between the installation
of a PV generator on the roof of a public building – with an
existing lightning protection system – and the installation on
the roof of a barn – without a lightning protection system.
Field installations also offer large potential targets due to
their large area module arrays; in this case, an external
lightning protection solution is recommended for this type of
system to prevent direct lighting strikes.
Normative references can be found in IEC 62305-3
(VDE 0185-305-3), Supplement 2 (interpretation according
to lightning protection level or risk level LPL III) [2] and
Supplement 5 (lightning and surge protection for PV power
systems) and in the VdS Directive 2010 [3], (if PV systems
> 10 kW, then lightning protection is required). In addition,
surge protection measures are required. For instance,
preference should be afforded to separate air-termination
systems to protect the PV generator. However, if it is not
possible to avoid a direct connection to the PV generator,
in other words the safety separation distance cannot be
maintained, then the effects of partial lightning currents
must be taken into consideration. Fundamentally, shielded
cables should be used for the main lines of generators to
keep induced overvoltages as low as possible. In addition,
if the cross-section is sufcient (min. 16 mm² Cu) the
cable shielding can be utilised to conduct partial lightning
currents. The same applies to the utilisation of closed metal
housings. Earthing must be connected at both ends of
cables and metal housings. That ensures that the main lines
of the generator fall under LPZ1 (Lightning Protection Zone);
that means that a SPD type 2 sufces. Otherwise, an SPD
type 1 would be required.
Utilisation and correct specication of surge
protection devices
In general, it is possible to consider the deployment and
specication of SPDs in low voltage systems on the AC
side as standard procedure; however, the deployment and
the correct design specication for PV DC generators still
remains a challenge. The reason is rstly a solar generator
has its own special characteristics and, secondly, SPDs are
deployed in the DC circuit. Conventional SPDs are typically
developed for alternating voltage and not direct voltage
systems. Relevant product standards [4] have covered these
applications for years, and these can fundamentally also
be applied to DC voltage applications. However, whereas
previously relatively low PV system voltages were realised,
today these are already achieving approx. 1000 V DC in the
unloaded PV circuit. The task is to master system voltages of
that order with suitable surge protection devices.
The positions at which it is technically appropriate and
practical to position SPDs in a PV system depends primarily
on the type of system, the system concept and the physical
surface area. Figures 2 and 3 illustrate the principle
differences: Firstly, a building with external lightning
protection and a PV system mounted on the roof (building
installation); secondly, an expansive solar energy system
(eld installation), also tted with an external lightning
protection system. In the rst instance – because of the
shorter cable lengths – protection is merely implemented
at the DC input of the inverter; in the second case SPDs are
installed in the terminal box of the
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Surge protection for photovoltaic systems
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