The Quality of The DC Cable Is An Important Factor in Determining The Performance of A Solar Photovoltaic Installation

The energy provided by a solar photovoltaic system depends not only on the efficiency of the modules, but also on other system components such as DC cables, connectors and junction boxes. When designing a solar farm, engineers must account for module-to-inverter losses to calculate the farm's overall performance ratio. Low-quality solar cables and connectors can cause a small increase in resistance and result in higher energy losses. When calculating lifetimes beyond 25 years, the loss of energy already harvested creates significant losses and can impact the profitability of solar projects.

High-quality solar DC cables are expected to function throughout the installation life cycle of approximately 25 years. The cost of replacing a defective installed cable is very high. Replacement costs increase considering the manpower required to disassemble, reinstall, and test the system. In addition, there are losses in power output and revenue generation. The cost of these cables and connectors is very small in the total cost. Since the differential cost of high-quality cables is negligible, it makes sense to invest at a higher initial cost and reduce the "total cost of ownership" of a PV plant.

Solar cables must be able to withstand various environmental conditions

And will continue to do so for a long time. High temperatures, UV radiation, rain, humidity, dirt, and infestation by moss and microorganisms are all serious challenges for solar cables. Cables tested to EN, TUV and UL requirements (120°C; 20,000 hours) can be used in ambient temperatures from -40°C to +90°C. Therefore, they should reach the target service life of 25 years.

Besides temperature, UV radiation is another important factor. Tests have shown that untreated material (without any color additives) will lose more than 50% of its properties in less than six months. To avoid this deterioration, fine soot particles are added to the plastic (causing the shell to appear black). These particles absorb UV radiation and convert it into heat. Therefore, optimum UV resistance can only be achieved with black solar cables with sufficient black carbon content.

A new European standard EN 50618 has been published for solar DC cables, which specifies cables for photovoltaic (PV) systems, especially those installed on the direct current (DC) side, with a nominal DC voltage of up to 1.5kV between conductors and between conductors and earth. These cables are suitable for years of permanent outdoor use in a variety of harsh conditions. Relatively stringent requirements are set for these products according to the expected harsh usage conditions. The standard of EN 50618 requires that the insulation and jacket of solar cables be low-smoke halogen-free, flexible tinned copper conductors, single-core power cables with cross-linked insulation and jacket. The testing requirements in EN 50618 are more stringent, the most important change is that all testing is done on the material of the finished solar cable to ensure that the product to be installed passes all the testing requirements. Solar cables need to be tested at a voltage of 11KV50Hz. The IEC standard for solar DC cables based on EN50618 is also in preparation.

To meet the stringent requirements of modern solar cables, the insulation and jacket consist of cross-linked polymers. Two different processes are available for crosslinking - a choice between electron beam crosslinking and chemical crosslinking. Chemical crosslinking is a process that cannot be stopped once started. Therefore, chemically cross-linked cables exhibit the same phenomenon as old car tires. They will harden and become porous. In contrast, electron beam cross-linked cables are irradiated with beta rays. This improves synthetic materials. Once the cable has passed through the electron beam, the cross-linking process is complete. These cables remain soft and resilient throughout their lifespan.

A solar cable is only as strong as its weakest link

That's why XSD Cable provides high-quality e-beam cross-linked solar cables. Produced in Switzerland, these high-quality solar cables meet all requirements: long service life, excellent weather resistance and investment security for facility operators. These are still installed in Europe. Compounds for insulation and sheathing materials are produced and developed in-house. With increased capacity over time, it today has the largest beta beam crosslinking facility in the world, contributing to the highest production of solar DC cables. XSD Cable first launched UL certified cables in 2018, 1500V DC cables for solar installations. Its production facilities are located all over the world, from junction boxes for module manufacturing to cable systems and connectors for solar photovoltaic installations.