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Trevor Manas started his lightning protection career at
Pontins in 1991 as an installation technician, learning
the ropes by working on various sites and doing physical
installations. Within two years, he was promoted to sales
engineer, where he was involved in site assessments, soil
resistivity surveys and compiling quotations. In 1996, Tre-
vor was promoted to the position of director and was in charge of ensuring
the company`s compliance with the earthing and lightning protection codes
of practice. In 1999, Trevor became the managing director of Pontins. In
2013, Pontins formed a partnership with DEHN Africa which gave Pontins
access to world class cutting edge lightning protection technologies.
Enquiries: Email
trevor@pontins.co.zaELECTRICAL PROTECTION + SAFETY
String Inverter
In case of string inverters, the power supply
cables act as equipotential bonding conductors
between the ‘local’ earth termination of the PV
array which was directly hit by lightning and
the ‘remote’ equipotential surface of the infeed
transformer. Partial lightning currents flow on the
ac lines, therefore the installation of Type 1 SPDs on
the ac side of the string inverters and on the low-voltage
side of the infeed transformer is necessary. Type 2 SPDs,
which mainly limit induced interference impulses, are sufficient on
the dc side of the string inverters.
Figure 10: PV System with central inverter.
Figure 11: PV System with string inverters.
Protection of data systems
The ability to obtain reliable data from remote maintenance equip-
ment via data cables is essential in the effective operation of the
PV Plant.
It is therefore important to provide adequate surge protection
to these data systems to prevent damage to the data system. The
string and inverter monitoring system, weather data acquisition unit,
anti-theft protection and external communication system, are based
on different physical interfaces. Surge protection devices specifically
suited to each type of interface must be selected.
Conclusion
In South Africa, the high lightning flash indexes,
coupled with the large size and vulnerability of
Free Field PV Power Plants, makes the correct
design and installation of the lightning and surge
protection systems imperative. Proper lightning
and surge protection for all systems gives enhanced
performance of these power plants. The service and
maintenance time as well as the repair and spare part
costs are also reduced. The use of DEHN lightning arresters
and surge arresters with their SCI (patented) disconnect technology
is recommended for PV Power Plants.
References
[1] SANS/IEC 62305-1, 2, 3: Lightning Protection
Standard.
Part 1: General principles.
Part 2: Risk management.
Part 3: Protection of the structure.
Part 4: Electronic systems protection.
[2] SANS 10313. 2012. Protection against lightning -
Physical damage to structures and life hazard.
[3] DEHN & Sohne - Lightning Protection Guide (3
rd
edition)
.
Note
IEC 62305 (part 3) Supplement 5. Lightning and Overvoltage
Protection for Photovoltaic Power Supply Systems (this has
not yet been adopted by the SABS standards committee but
the writer believes that it can be considered as good practice
and would recommend the use of this supplement).
Electricity+Control
August ‘16
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