Electrical hazard analysis during assembly, integration and testing of solar arrays

The development of photo-voltaics over the last decade shows an increase of almost a factor two in efficiency from mono-crystalline silicon to the modern multi-junction solar cells. Recent developments in system optics using concentrators, or splitting up spectral bands through different light paths to different types of solar cells, prove that efficiencies of up to 60–70% are achievable. This significant growth in efficiency of solar arrays, however, increases the focus on lethal electrical biasing incidents. Therefore in this article an inventory of light sources, electrical hazard conditions and solar cell types is provided. Typical solar array sections, voltage bias cases, leakage resistance and light sources are chosen to assess the magnitudes of electrical direct currents. Photometric theory is applied to solar cell assemblies and linked to a simulation model for the electrical performance of solar arrays. This enables a worst case static analysis for the ultimate electrical hazard without any precautions: a wet hand touching a positive connector pin or string endbar in combination with a ‘good‘ electrical grounding of the physical body of the engineer. As a new result, simple equations are derived to estimate the hazard currents for the full scope of solar arrays. The validity to apply these equations is extensively verified by a sensivity analysis over all relevant parameters.