Type tested, modular junction boxes and distribution boards key to reliable, cost-effective solar power installation

The components used in photovoltaic installations face challenging environmental conditions. On roofs they are typically exposed to sun, rain ice and snow. They have to operate both in the high temperatures in summer and in the freezing cold of winter. And the components also have to be resistant to constant UV radiation. Hensel distribution boards meet all of these requirements and the stringent standards governing photovoltaic installations.

Hensel’s product range includes all of the necessary installation and distribution board systems for photovoltaic plants from PV generator junction boxes to PV inverter collectors and extensive accessories. The modular pre-wired ENYSUN photovoltaic generator junction boxes are type tested to IEC 60 364-712, and plug-in ready. This dramatically reduces installation costs. Further, they can be supplied with optional ‘combi’ climate glands that incorporate a special membrane to resist condensation and to ensure the IP65 sealing is maintained.

For the furniture business installation, Hensel provided the planning for plant’s sub-distribution boards and the main distribution board, while Elektro Dittmaier of Zellingen, Germany, was responsible for AC-side project planning, installing, commissioning and plant monitoring. Photovoltaic specialist Guido Dittmaier comments: “We installed our first photovoltaic plant eleven years ago, and we have used Hensel products right from the very beginning. The new ENYSUN series makes our work easy, as it means we can use pre-mounted and type-tested systems. It saves time in procurement, in mounting and in commissioning of the power plant.”

A total of 4,050 solar modules with a total capacity of 303.75kWp were wired in 14 ENYSUN photovoltaic generator junction boxes. The ENYSUN junction boxes were delivered pre-wired and plug-in ready, simplifying the installation.

Forty inverters with a total capacity of 266kW convert direct current from the solar panels into alternating current. Using a higher number of smaller inverters aids reliability, since power loss is minimized in the event of a failure of any single inverter. The plant is able to feed the maximum possible energy into the grid at all times.

Five Hensel ENYSTAR sub-distribution boards were installed as a link between the inverters and the main low voltage distribution board, with the inverters feeding into a ‘collector’. The modules are pre-fabricated so that they can be installed quickly and easily, with the inverter collectors simply needing to be connected on site. EMC-compliant busbars, protection systems and connection terminals are pre-installed. The busbars have the same current carrying capacity as the phase conductors, and are rated to handle the harmonics produced by the inverter as well as the asymmetrical load limits. The sub-distribution boards also reduce the cable load significantly, since the main distribution board has only five feeds from the inverter instead of the 40 feeds.

The low-voltage main distribution board provides the link between the local power supply company’s grid and the furniture business’s photovoltaic plant. All five feeds run to Hensel low-voltage switchgear assemblies, with the decision taken to use motor-driven circuit breakers rather than contactors. These circuit breakers met the requirements stipulated by the local power supply company offering four phase switch-off (0/30/60/100%) in the main distribution board.

Jügen Neppel, who heads up Hensel’s regional office in Würzburg, Germany comments: “A circuit breaker does not require continuous additional power in operation, as it is normally never switched. Contactors on the other hand require constant holding power and thus create operational expenses. If a contactor fails it needs to be replaced before the line can work once again. Plant availability and power supply reliability are higher using motor-driven circuit breakers, as they can also be switched manually if needed.”

In addition to installing and commissioning the power plant, Elektro Dittmaier is also responsible for the maintenance and monitoring of the Herne PV plant. To be able to provide this service cost-effectively, it was important that all components offered assured reliability over the long term – a further factor in the selection of the Hensel distribution boards.

Safety was another key consideration. Dittmaier comments: “Safety always has to come first for us, and Hensel is the only supplier of safe, standardised and practical distribution board solutions for the assembly of photovoltaic plants with appropriate test certificates.”

In addition to assured reliability, plant operators also place great importance on quick component replacement during maintenance, to keep availability high and maintenance costs as low as possible. The modular design aids speed of installation, while the availability of the products through electrical wholesalers enables Elektro Dittmaier to react quickly when service is needed. This capability was ably demonstrated when the capacity of the plant was expanded by a further 85kWp.