WCA January 2012

It covers single conductor, insulated and integrally or non-integrally jacketed, sunlight resistant, photovoltaic wire in several temperature and voltage ratings for interconnection wiring of grounded and ungrounded photovoltaic power systems. The standard UL 4703 is based on the service entry cords USE-2 and speci- fies some additional requirements for photovoltaic cables. It applies for solar cables in North America. These UL-requirements are quite different from the German specification. The UL standard leaves more freedom for the manufacturer as far as the cable construction and the selection of materials is concerned. One or two insulation layers can be chosen optionally as well as a “skinned” single layer construction.

1 Shoulder with sufficient depth for testing the insulation 2 Needle of spring steel 3 Sample

❍ ❍ Figure 3 : Arrangement for penetration test on completed cable

The document [2] specifies a flame propagation test on the completed cable according to IEC 60332.1. 4.8 Absence of halogens In the case of fire, acids caused by the smoke of halogenated materials are a serious danger for people’s health as well as for the function of electric and electronic devices. In former times halogen free cables were required in public areas such as hospitals, airports and other similar structures.

For two-layer construction, as specified in the DKE-document [2] , several combinations of wall thick- nesses are allowed in UL 4703. But in each case the total sum of wall thickness will be higher than specified in the German specification (see Table 1 ). Thus the diameter for the same conductor cross section will be higher which reduces the suitability for several connectors. And the increased need of insulation compound will add to the production cost.

❍ ❍ Table 1 : Wall thicknesses acc. to UL 4703

Dimension

AWG 10 – AWG 18

AWG 2 – AWG 9

But due to the increasing importance of electronics in all areas of every- day life, this quality is increasingly required in industrial premises, too. As far as for solar cables, this characteristic is especially important for solar power devices on residential buildings. Several tests have to be performed to prove the absence of halogens in solar cables. Electrical conductivity and pH value of the smoke are to be quantified according to European standard EN 50267-2-2. The content of chlorine and bromine is determined according to EN 50267-2-1 and a special test is developed for the content of fluorine in Annex C of the discussed specification [2] . 5 UL 4703 Standard In 2005 the American Underwriters Laboratories (UL) published the UL subject 4703 “Photovoltaic Wire” [3] .

Single layer

1.52mm/60mils

1.91mm/75mils

1.91mm/75mils (1.14mm + 0.76mm)

2.28mm/90mils (1.52mm + 0.76mm) (1.14mm + 1.14mm) (1.52mm + 1.14mm)

Skinned

2.28mm/90 mils 2.66mm/105mils

Double layer

❍ ❍ Table 2 : German specification versus UL 4703

DKE [2]

UL 4703 [3]

Parameter

Cable Type

Solar Cable

Based on RHHW/USE-2

Cold Bend/Cold Impact

-40°C

-40°C

Hot Pressure Test

+140°C

+121°C

Ageing Test

+150°C

+121°C

Humidity Test

1000h/90°C/85% rel.

Not required

Dynamic Penetration

Ambient temp, 150N * √_

Not required

UL 1581 sec. 1060 UL 1581 sec. 1080 UL 1581 sec. 1061 UL 1581 sec. 1100

Fire Performance

IEC 60332.1.2

EN 50267-2 EN 60684-2

Halogen Free

Not required

Weathering/UV-Test

HD 605 S1/A1

UL 1581 sec. 1200

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Wire & Cable ASIA – September/October 2007 January/February 2012