Field test results of serial DC arc fault investigations on real photovoltaic systems

DC arcing faults pose a safety risk in already existing photovoltaic systems. Due to the aging of the photovoltaic system components enhanced by environmental factors and the high DC voltages, long-lasting arc faults can occur and may cause serious damage. Conventional fault protection methods like circuit breakers or fuses - are only able to clear faults if they carry a large fault current. Compared to arcing faults in AC installations DC arcing faults in photovoltaic systems have a bigger hazard potential. This is mainly based on the favorable conditions of existing. That is first of all missing zero-crossings of the current and the fact that a solar generator regarded as a source of energy cannot be turned off. Secondly a solar generator is a distributed energy systems with a big amount of potential places of origin for arc faults. Because of the non-linear current-voltage output characteristic of photovoltaic systems a lot of arc faults cannot be detected or even extinguished by common fault protection methods. Moreover it does not only ensure a higher arc-stability but also a wider range of stable arc operating points. Furthermore ambient conditions (e.g. solar radiation, temperature, etc.) and the arc length extend the range of stable arc operating points tremendously. For those reasons the characterization of DC arc faults in photovoltaic systems by means of measurement in real existing photovoltaic systems is indispensable. Especially under consideration of the increasing number of accidents with photovoltaic systems involved. This paper will include a general description of the infrastructure used for measuring and recording arc voltage and current. In addition, the experimental test setup used to insert a series arc fault within a PV system and to generate comparable results under safe conditions will be explained in detail. Furthermore the field test results of serial DC arc fault investigations in photovoltaic systems with different module technologies and taking into account a wide range of environmental conditions and a huge variety of different fault locations within the solar generator will be presented.