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54 Wire & Cable ASIA – November/December 2015
3.3.1 The differences to TUV 1169/2007.8
The significant differences between UL and TUV are:
• Halogenated compounds are permitted in UL4703
• The required flaming test UL1581-1060 is more
demanding than IEC60332-1
• No differentiation between DC and AC in UL4703
• 1,000V (or 2,000V) is permitted, which is more
future-orientated
• Aluminium wires are permitted in UL4703
• No differentiation U0/U in UL4703
4 New challenge for the cable industry
4.1 TUV and UL approved cables 2006–2013
In 2006 the module manufacturers started to think globally.
The new marketing requirement was to manufacture one
type of photovoltaic module with all relevant approvals to
sell them on all markets.
The challenge was to create a cable which could combine
the opposed specifications of UL (PV / USE-2) and TUV
1169. Particularly the following discrepancies had to be
overcome.
• Halogen-free compounds are highly filled with flame
retardant minerals. The physical properties required by
UL are a challenge for this kind of compound
• Passing the flame test required by UL is easy for
halogenated compounds but difficult for halogen-free
compounds
• The long-term stability test of UL is a real challenge
for filled compounds because the flame-retardant
additives are hygroscopic
However, it was possible to comply with all these
requirements.
4.1.1 The first solution
The outstanding characteristics of this design are:
• Three-layer extrusion in one pass (implicated by
increasing pricing pressure in the PV industry)
• Special developed polymer as separator
• Separable layers which have been required by many
customers (UL definition: “Thermoset insulation having
a jacket”)
• The difference of these two cable families are different
layers thicknesses because the UL has a higher
requirement for the insulation thickness
• All compounds are thermoset (electron beam
crosslinking)
5 The next step
5.1 New requirements
In 2013 the new requirement of the PV industry was to
increase the system voltage to save cable cost and to
increase the efficiency of the PV systems. The voltage
rating of the first generation of PV wires according to
TUV1169 was based on generic industrial cable standards.
The standard voltage rating of low voltage cables in the
CENELEC and IEC is U0/U = 600/1,000V AC or 900/1,500V
DC.
The nominal voltage rating of the new generation
photovoltaic wire is U0/U = 1,000/1,000V AC or
1,500/1,500V DC. In the meantime TUV Rheinland
developed 2Pfg1990/2012, which considers the new
requirements.
5.2 New generation of UL4703 1,000V/TUV 1,500V
DC cables
The outstanding characteristics of this design are:
• Four-layer extrusion in one pass (implicated by further
increasing pricing pressure in the PV industry)
• All compounds are thermoset (electron beam
crosslinked)
• Layers not separable (UL definition: “Composite
insulation without a jacket”)
• Approvals: UL (1,000V)/TUV (2Pfg1990)/CSA 22.2
No 271-11
6 The way to CENELEC and IEC
6.1 CENELEC
In 2011 the German National Committee for PV wires and
cables started to work out a revision of VDE-AR-E 2283-4
“Requirements for cables for PV systems”.
The target was now to apply this draft as a
new work item to CENELEC TC20. The main topics
were:
• Increasing the system voltage
• Adapting test procedures to the new voltage level
The result of this work is EN50618, which was published as
a final draft in August 2014.
❍
❍ Figure 2 : Definition of U0/U
❍
❍ Figure 4: New design
GND
❍
❍ Figure 3: Optimised design of a UL4703 and TUV1169 or
TUV1169 wire
Jacket
Separator
Insulation
Conductor
Two-layer jacket optimised for
mechanical properties and flame
retardance
Two-layer insulation. Electrical properties
and flame retardance
Conductor