Press Release

Photovoltaic Systems: TÜV Rheinland Presents Research into Safe Switching Operations

Research project completed successfully / New test specifications to be presented at conference in April 2016
Led by TÜV Rheinland, numerous experts from the industry have been working for more than two years on technical requirements for switch devices in photovoltaic systems. The results of the PV Firebreaker joint project are now available. This project was carried out by TÜV Rheinland together with its partners E-T-A Elektrotechnische Apparate, Eaton Industries and SMA. The results will now be incorporated into the work of international standardization committees.
Since summer 2013, the experts have been working on requirements to ensure that switch devices in photovoltaic systems function faultlessly throughout the service life of the complete system. The safe function of photovoltaic components plays a decisive role in terms of acceptance and distribution, as well as in the returns generated by photovoltaic systems.
“So far, there have been no sufficiently specific technical requirements for switch devices, especially for what are known as modular switches that are installed in such systems. That has changed now that the research project is complete,” explains Ralf Martin Müller, business field manager at TÜV Rheinland and project leader. “Together with our project partners, we have identified and analyzed various faults and risks and assessed them in terms of their impact. Appropriate testing requirements have now been derived from the results in order to enable switch device manufacturers to design safe and reliable switches and disconnectors.” The results are being prepared for the national and international standardization committees and will be submitted shortly. TÜV Rheinland will give the sector some initial insight into the new test specifications at a conference in Cologne in April.

Laboratory experiments as a basis for results
During the project, researchers assessed the effects of faults and determined the potential stresses on isolating devices, such as reverse currents, voltage doubling at the contacts or transient overcurrents. The faults analyzed include short circuits of the entire string, installation errors due to reverse polarity of the connectors, induced impulse voltage caused by factors such as lightning strikes or asynchronous switching behavior on the part of modular switches.
The technical standards that are currently available do not offer adequate solutions to many of the identified fault risks, as in comparison with the traditional direct-current systems, particular stresses and faults can occur in photovoltaic systems. “We have developed testing programs to recreate the faults. In the individual programs, the switch devices have been tested in accordance with various criteria. We have evaluated the findings that we obtained from these tests and then defined a test method,” explains TÜV Rheinland expert Ralf Martin Müller.
Both components from project partners and switch devices available on the market were used in the laboratory tests. In order to examine long-term stress in the field, the experts conducted continuous load tests under various environmental and temperature influences. To ensure that the laboratory experiments can be performed later in an economically viable manner, various faults were grouped into individual test scenarios, for example.
The PV Firebreaker joint project was sponsored by the German Federal Ministry for Economic Affairs and Energy (FKZ 0325596).