WCA January 2012

thermal and mechanical load. The test is performed on the completed cable according to the test method described in IEC 60811-3-1. Test temperature is +140°C; the load is applied for four hours. Solar plants must be able to work under extreme weather conditions. Thus, the components are tested not only for high temperature but also for low temperature performance. In the German specification [2] this is taken into account with high requirements for the cold bend and cold impact test. These tests are performed according to IEC 60811-1-4 at -40°C. But additionally the cold impact test is performed with increased height as well as increased weight of hammer and intermediate piece. 4.4 Short and long term ageing at high temperature A short term ageing test is required at +150°C with a duration of 168 hours for the insulation as well as for the jacket material. Additionally, an Arrhenius test has to be performed where the materials have to withstand 20,000 hours at +120°C (see Figure 4 ). This enables manufacturers to guarantee a lifetime of 25 years in the specified operating conditions. To reveal the performance under different environmental conditions, a weathering and UV resistance test according to HD 605/A1, part 2.4.20 is required as well as a damp heat test according to EN 60068-2-78. 4.6 Dynamic penetration test A special penetration test was developed to prove the stability of the cable jacket and insulation against mechanical loads. It is described in Annex E of the dis- 4.3 Cold bend test and cold impact test 4.5 Weathering/UV resistance/ humidity

❍ ❍ Figure 1 : Pressure test at high temperature on the solar cable

❍ ❍ Figure 2 : Hot elongation test

cussed specification [2] . As shown in Figure 3 , a steel needle is pressed onto the cable sample. The load is continuously increased until the needle contacts the cable conductor, indicated by a low voltage electrical circuit. The load in the moment of contact is derived by a load cell. This test simulates mechanical loads on the cable that could be caused by any object or device falling on the cable or by animals outside. 4.7 Fire performance Although the danger of fire propagation in outdoor applications such as solar plants is not a great risk for the safety of people, a good fire performance is required to protect the technical equipment.

The solar cable according to DKE is a two-layer insulated single core cable with a minimum wall thickness of 0.5mm in each layer. The most important tests required in this specification [2] are discussed in the following clauses: 4.1 Temperature range Solar cables according to the German specification [2] are defined for an environmental temperature range from -40°C up to +90°C. The maximum conductor temperature is specified at +120°C. 4.2 Hot pressure test The purpose of this test is to check the mechanical stability of the cable insulation and jacket under high

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Wire & Cable ASIA – September/October 2007 Wire & Cable ASIA – January/February 12