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Wire & Cable ASIA – September/October 2007
66
January/February 2012
Abstract
The recent growth of the renewable energy market applies
to both wind energy as well as to solar energy. In many
countries this growth is supported by governmental
subsidies.
Outdoor applications in renewable energy plants demand
high thermal and mechanical requirements from cables
and other components. Therefore, some national
standardisation bodies defined general requirements for
cables used in solar plants.
In 2005 UL 4703 was published in the USA. In Germany a
joint working group “Cables for Photovoltaic Application”
was established in the same year, which resulted in a
specification published in February 2008.
The performance requirements in high temperatures have
been set very high for cables. Various German institutes
accepted this specification and now offer certifications for
it. There has been a huge demand in the European as well
as Asian markets for such certified cable.
Due to the differences the UL 4703 requirements cannot
be combined together with the German specification.
The different solar-cable requirements have advantages
as well as disadvantages in respect to the specific
regional conditions.
1 Introduction
The renewable energy market is growing rapidly. A
tenfold increase for the next five years is anticipated by
Merill Lynch
[1]
.
This growth applies to wind energy as well as to solar
energy. Due to public interest, a number of governments
have decided to support the renewable energy economics
with large amounts of subsidies. Thus, even a further
increase in this market can be expected.
2 External Conditions
The photovoltaic market is a very specific market. Various
national regulations are to be taken into account. The
system size can vary from a small home power supply with
a nominal power of few kilowatts up to large centralised
solar plants in the Gigawatt range.
The components used in these systems must be suitable
for these specific applications.
One common determining factor for all photovoltaic
power systems is the outdoor use, which brings along
high temperatures and, of course, high UV radiation.
Weathering and humidity need to be taken into account,
as well. Furthermore, safety and reliability aspects are
very important.
The improvements of the solar panel technology define
the electrical performance of components. Usually solar
systems are working with low voltage direct current, and
the panels are switched in parallel.
Thus, the current is the determining electrical parameter.
In terms of cables, this results in different conductor cross
sections.
3 Common Specification of German
Technical Institutes
In 2005 the German national electro-technical
standardisation body, DKE, established a working group
called “Cables for Photovoltaic Application” which resulted
in a public specification.
This document was published in February 2008
[2]
.
Due to the close cooperation between different institutes,
this specification is identical to the TÜV-Specification
2 PfG 1169/08.2007 and the VDE-Specification E PV
01:2008-02.
DKE-Subcommittee UK 411.2 released the document for
publication and application, but due to CENELEC rules it
was not adopted as a national standard in Germany.
4 Technical Details of the German
Specification
In this German specification
[2]
the requirements have been
raised to a very high level regarding the high temperature
performance of cables. Additionally, high mechanical
stability is required; the cable has to be flame retardant
and free of halogens.
To meet this specification the manufacturers generally
use halogen free flame retardant cross linked polyolefin
copolymers as material for insulation and jacketing.
Cables for
Photovoltaic Applications
By Jorg Bor of Freidrich Lütze GmbH & Co KG, Stefan Grunwald of Lutze Inc,
and Ilona Hirtz of Kabelwerke Villingen GmbH