sparks
ELECTRICAL NEWS
october 2014
16
contractors’ corner
PHOTOVOLTAIC (PV) systems have become a significant sector
within the energy market, as attested to by the increasing
number of PV systems with domestic and commercial applica-
tions. Given they are frequently installed in exposed places,
such as rooftops, and are subject to climatic influence, meas-
ures to protect the sensitive electronic system components
from failure due to lightning flashes and surges are essential.
Lightning surges in the PV system can damage PVmod-
ules and inverters and have serious consequences for the
operation of the system. Firstly, high repair costs, for example,
those of the inverter, have a negative effect; and, secondly,
the system failure can result in considerable profit cuts for the
operator of the plant.
Lightning and surge protection for PV systems in buildings
By Alexis Barwise, managing director at Dehn Protection South Africa
strikes, and to take the results from this into
account when designing the PV system.
Buildings without external lightning
protection system
On a building without external lightning
protection system, possible installation sites
of the surge protective devices can be at the:
• Direct current (dc) input of the inverter;
• Alternating current (ac) output of the in-
verter; or
• Low voltage (LV) supply.
Buildings with external lightning
protection systemand separation
distance kept
The PV systemon the roof surface should be
designed taking into account the existing
external lightning protection system and
installed within its protection zone. By using
suitable air termination systems, such as air
ter0mination rods, direct lightning strikes into
the PVmodules can be prevented. If neces-
sary, additional air termination rods must
be arranged within the protection zone and
must not cast any shadow on the modules.
An essential part of a lightning protection
system is the lightning equipotential bonding
for all conductive systems and conductors.
The requirements of lightning equipotential
bonding are met by the direct connection of
all metal systems and the indirect connection
of all live systems, via lightning current arrest-
ers. This bonding should be performed near
the entrance point of the systems and con-
ductors into the structure in order to prevent
a penetration of partial lightning currents into
the building.
Buildings with external lightning
protection systemand separation distance
not kept
Often PVmodules cover the whole roof
in order to generate the highest possible
profit, oftenmaking it impossible to keep the
separation distance. At these points, a direct
conductive connectionmust be provided
between the external lightning protection
system and the metal PV components. In
this case, the effects of the currents carried
into the structure via the dc conductors also
have to be taken into account and lightning
equipotential bonding ensured. This means
that the lightning current carrying dc conduc-
tors have to be included into the lightning
equipotential bonding. Lightning equipoten-
tial bonding also has to be implemented also
for the LV input. If the distance between the
PV inverter and LV input is not greater than
five metres, then the ac output of the inverter
is also protected.
Enquiries: +27 11 704 1487
PV systems can be installed on buildings with or without
existing lightning protection. Some buildings, whether due to
their location, construction type or utilisation, are more sus-
ceptible to a lightning strike, and as such, need to be equipped
with a permanently effective lightning protection system. It is
important to note, however, that the installation of PVmodules
on buildings does not increase the risk of a lightning strike.
Nevertheless, there may be an increased danger for the electric
facilities of the building in the event of a lightning strike; based
on the fact that, due to the wiring of the PV lines inside the
building in existing risers and cable runs, strong conducted
and radiated interferences may result from lightning currents.
Therefore, it is necessary, to estimate the risk of lightning
A link to your
Wireman’s License
Phone +27 11 827 4113 or go to:
and click on the P &T Technology logo.
