EOW March 2014

Technical article

Development of the cable for photovoltaic power generation systems By Arifumi Matsumura*, Masaki Nishiguchi Shigeru Kubo, Fitel Photonics Laboratory, Furukawa Electric Co Ltd, Japan

Abstract Furukawa has developed a cable for photovoltaic power generation systems, which meets the requirements of the TÜV 2Pfg1169/2007 Standard [1] and the JCS4517 Standard [2] . A cable for photovoltaic power generation systems, which meets the requirements of these standards, requires that insulating materials and sheath materials be made of halogen-free materials. In addition to that, the cable requires vertical incombustibility, high-temperature heat resistance, low-temperature charac- teristics, and acid resistance. Furthermore, a temperature index is required to be more than 120ºC, because temperatures in the working environment range from −40ºC to +90ºC. A temperature at which an aging residue percentage reaches 50 per cent after 20,000 hours is required to be higher than 120ºC. In particular, excellent heat-deterioration characteristics are required. At this time, cross-linked polyethylene was used as an insulator of the cable; highly incombustible cross-linked polyolefin was used as sheath materials. As a result, this made it possible to meet the requirements of the above-mentioned standards. In addition, it was confirmed that there is no problem in putting this cable to practical use in terms of peeling characteristics and bleed characteristics. Furthermore, it is possible to manufacture this cable without using special bridging equipment such as electron-beam irradiation machines. This cable is very advantageous in terms of costs and response to mass production.

1 Introduction In recent years, while there has been a growing interest in environmental problems all over the world, power generation activities by using renewable energy such as wind power generation, photovoltaic power generation and biomass power generation have become very active. For photovoltaic power generation, power generation facilities on the scale of more than 1 megawatt, called ‘mega solar,’ have rapidly begun to become widespread. In the future, demand for the cables to be used in these power generation facilities is expected to increase. At present, unique standards are used in each region to ensure the reliability of electric wires used for these power generation facilities. In Europe, there are the TÜV 2Pfg1169 standards while the UL4703 standards [3] are available in North America. In recent years, the JCS4517 standards have been established in Japan on the basis of the TÜV 2Pfg1169 standards. Unique standards were established in each region, and there is an increasing demand for compatible cables that meet all standards. On the other hand, the development of less expensive cables is called for greater proliferation. At present, demand for low-cost cables is much higher than demand for integrated cables. Against the background of the above- mentioned circumstances, Furukawa has developed a cable that meets the requirements of the TÜV standards and the JCS standards.

2 A Newly Developed Cable for Photo- voltaic Power Generation There is a hot-set property as one of the mainly required properties of a cable for photovoltaic power generation, which corresponds to the TÜV standards and the JCS standards. In an incombustible halogen-free electric wire of polyolefin, electron beams are usually irradiated to satisfy the standard of hot-set properties. However, in a future mega solar facility, the capacity of an electric current will become larger. Namely, the size of a cable is expected to become larger. There is a limit to the response by electron-beam irradiation. In addition, as far as a small size of a low electric current is concerned, the cost of irradiation equipment itself is high, and non-electron beam bridging is called for. Therefore, this cable meets the standard of hot-set properties in the bridging method that did not perform electron beam irradiation in polyolefin materials. The main physical properties of a newly developed cable for photovoltaic power generation are introduced below. 3 Test Method 3.1 Hot-set Test A hot-set test was performed in conformance to the IEC60811-2-1 standards. An insulating tube-shaped piece and a sheath tube-shaped piece were cut out from a cable. The test pieces were hung at 20ºC in an oven. A load of 20 N/cm 2 was applied to the test pieces.

191

www.read-eurowire.com

March 2014