Norbert Henze - Fault currents and protection techniques in photovoltaic systems

Theoretical Considerations of the Use of Fuses in Photovoltaic Systems

Norbert Henze (1), Peter Funtan (1)

Fraunhofer Institute for Wind Energy and Energy System Technology IWES, Area: Systems Engineering and Grid Integration, Königstor 59, D-34119 Kassel  (1),,

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The use of fuses in photovoltaic systems is being controversially discussed among experts. On the one hand, the proper operation of the system is not supposed to require the use of fuses and in addition is considered a possible source of error. On the other hand, there is the insecurity that inadmissibly high currents may flow through the strings concerned even in regular operating conditions, e.g. in case of shading and partial snow cover [1]. Non-compliance with quality standards regarding modules and conductions or inadequately implemented installations are proven to be additional sources of error which have to be included in the considerations. Furthermore, discussions on deviating reverse current behaviour of different module technologies, missing information about securing the strings on the part of the module manufacturers or the necessity to apply the fuses only in case of certain converter concepts, contribute to the uncertainty. Missing regulations for dimensioning and not yet existing standards for solar fuses complete the present confuse situation.

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