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With an annual newly installed separation distance
capacity of some gigawatts, free s rolling sphere radius pro-
field PV power plants are becom- depending on air-termi- tective
angle
nation rod
ing an integral part of modern the class of LPS
power supply systems in many
countries. Today large-scale power
plants with a capacity of 100 MW
and higher are installed which are
directly connected to the medium
and high-voltage level. As an inte-
gral part of a power supply system,
photovoltaic systems must ensure Figure 9.19.1 Rolling sphere method vs. protective angle method for determining the protected volume
stable grid operation. In addition,
possible production losses, which negatively affect the annual be taken for PV systems > 10 kW of objects with alternative
performance ratio of the power plant, are recorded by the yield renewable power supply systems.
monitoring system. Consequently, the investment volume and The risk resulting from a lightning strike must be determined
a minimum service life of 20 years require that the risk result- according to the IEC 62305-2 (EN 62305-2) standard and
ing from a lightning strike be assessed and protection meas- the results of this risk analysis must be considered at the
ures be taken. design stage. For this purpose, DEHN + SÖHNE offers the
DEHNsupport software. A risk analysis performed by means of
Risk of a lightning strike to structures such as PV this software ensures a technically and economically optimised
power plants lightning protection concept which is understood by all par-
There is a connection between the solar radiation, air humidity ties involved and offers the necessary protection at reasonable
and frequency of lightning discharges. Regions with a high so- costs.
lar radiation and air humidity are more susceptible to lightning
strikes. The regional lightning frequency (lightning strikes per Measures for protecting PV power plants from
square kilometres / year) and the location and size of the PV lightning interference
power plant form the basis for calculating the probability of To ensure effective protection, a lightning protection system
lightning strikes to the plant. PV systems are exposed to local with optimally coordinated elements (air-termination system,
weather conditions such as thunderstorms over decades.
earth-termination system, lightning equipotential bonding,
surge protective devices for power supply and data systems)
Necessity of a lightning protection system is required.
Damage to PV systems is caused both by the destructive ef-
fects of a direct lightning strike and inductive or capacitive
coupling of voltages caused by the electromagnetic lightning Air-termination system and down conductors
field. Moreover, voltage peaks resulting from switching opera- To prevent direct lightning strikes to the electrical systems of
tions on the upstream a.c. system can cause damage to PV a PV power plant, these systems must be located in the pro-
modules, inverters, charge controllers and their monitoring and tected volume of air-termination systems. Design according
communication systems. to the German VdS 2010 guideline is based on class of LPS
Economic damage leads to replacement and repair costs, yield III. According to this class of LPS, the rolling sphere method
loss and costs for using the reserve power of the power plant. (Figure 9.19.1) as per IEC 62305-3 (EN 62305-3) can be
Lightning impulses also cause premature ageing of bypass di- used to determine the number of air-termination rods. These
odes, power semiconductors and the input and output circuits air-termination rods form a protected volume above module
of data systems, which leads to increased repair costs. racks, operations buildings and cables. Due to the inductive
In addition, network operators place requirements on the coupling of interference, it is advisable to install generator
availability of the energy produced. In Germany, these require- junction boxes mounted on module racks and decentralised
ments are based on e.g. the new Grid Codes. Banks and insur- inverters as far as possible from air-termination systems. The
ance companies frequently also require to consider lightning high masts on which CCTV systems are installed also act
protection measures in due diligence analyses. The German as air-termination systems. The CCTV system itself must be
VdS 2010 brochure (Risk-oriented lightning and surge protec- mounted in such a way that it is located in the protected vol-
tion) published by the German Insurance Association (GDV) ume of the mast. All down conductors of these air-termination
requires that lightning protection measures (class of LPS III) systems must be connected to the terminal lugs of the earth-

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