Fraunhofer ISE presents test stand for arc fault detectors

A modular test stand for solar inverters with integrated arc detectors has been developed by the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany. According to a press release, it can be used to perform tests in accordance with the IEC 63027 standard, which was published on May 3. This test standard, in the development of which ISE was involved and the basic features of which correspond to the revised US standard UL 1699B, eliminates »some of the weaknesses of the old US standard, which did not simulate real operation sufficiently.« According to ISE, this resulted in both undetected arcs and false alarms.
Arcing occurs as a result of faulty contacts on the DC side of PV systems, for example at defective solder joints in solar modules or in the inverter. Although they occur infrequently, they pose a significant fire hazard due to the high temperatures involved. In the USA and some other countries, arc fault detectors have therefore been mandatory since 2011, whereas in Europe only a few manufacturers offer inverters equipped accordingly. However, the insurance industry in particular is also working towards an obligation here.
The test stand at Fraunhofer ISE does not use solar modules, but an electronic DC source for simulation. A contact point, which can be pulled apart in a precisely defined manner, is intended to reproducibly simulate the conditions of a faulty contact. The modular design is intended to enable various test scenarios for string inverters; module inverters and string collectors can also be tested.
According to the new standard, an arc detector must ensure that a shutdown time of less than 2.5 seconds is maintained at an energy between 200 and 750 joules. Automatic reconnection is permitted four times within 24 hours; the fifth time this must be done manually.
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