The safety and efficiency of photovoltaic systems depends largely on the quality of cable management and the use of suitable and appropriate fastening and mounting solutions. The fixing of lines, cabling and electrical wire serves primarily to bear loads and in turn to protect cabling and integrated strain reliefs (e.g. connectors) from mechanical overloading.
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Moreover, fastening elements should prevent (as well as not cause) chafing of cables as well as abrasion of insulation. Only appropriately designed and compatible mounting brackets can meet these many requirements.
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UV resistance is important
Various aspects should be taken into account in the selection of suitable cable protection pipes, namely (and at the very least) UV resistance, fire protection properties, pressure resistance and, if necessary, water resistance of the pipes. Alongside metal pipes, which are frequently unsuitable for reasons of weight, long-term UV-resistant corrugated pipes made of PP plastic are the best compromise for above-ground use. These have a UV resistance of up to 20 years.
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Rigid and flexible pipes made of HDPE plastic are often preferred for underground installation in ground-mounted open-air systems. Moreover, UV-resistant special versions can serve as a hybrid solution for all types of application. Whatever the approach, it is vital to request the technical data sheets of the cable conduits from suppliers, and to get the details on their UV resistance.
Cable ties suffer in the sun
Cable ties do not cope well with prolonged exposure to sunlight and UV-resistant plastic solutions are preferable in the long term to maximise service life, even under extreme conditions. For open-space solar parks and similar installations in Central Europe there is a clear recommendation for high-performance cable ties made of long-term UV-stabilised PA6.6.
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For the reasons mentioned above, only cable ties approved for outdoor use with corresponding UV resistance should be used. In the course of installation, it is imperative to request the technical data sheets for cable conduits from suppliers and to get the details on their UV resistance. Practice has shown that standard cable ties, which are typically UV-resistant for only three years, are often mistakenly used.
Strain reliefs should not be neglected
Strain reliefs protect cable connections from mechanical overload. These are often already incorporated into the respective equipment (plugs, GAK, module connection boxes). However, even these can only absorb a certain amount of force. For example, in DC connectors for cable diameters of 4-9 millimetres, the integrated strain relief can withstand at least 80 Newtons (according to the standard IEC/EN 628529). The respective installation type must be able to withstand additional loads above this figure. (HS/TF)
The author: Thaddäus Nagy is the Executive Director of EMC-direct. Nagy and his team have been involved in the construction of numerous large-scale open-air systems across Europe. Products from the specialist supplier for cable protection and fastening technologies, based in Dorsten near Gelsenkirchen have been used among others in large solar projects in Austria and Denmark.
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