Protection against electric shock in photovaltaic generators (PVGs) with active protective measures requires an in-depth knowledge of the electrical behaviour of PVG insulation and PVG response under operating conditions with insulation faults. On the one hand, this knowledge can be obtained with an equivalent circuit model that characterises this insulation. The model presented can be used to: (i) evaluate PVG insulation resistance and leakage current; (ii) analyse potential hazards for the general public: (iii) design the best means of protection. On the other hand, this article also describes the insulation of a functioning PVG, and its reaction to meteorological variables (MVs) in laboratory and field conditions. Test results highlight those MVs that have a greater influence on PVG insulation as well as the relation between weather and insulation. This type of characterization is crucial when it comes to testing the operating capacity of the protective devices used in active protective measures against electric shock under different meteorological conditions. (C) 2009 Elsevier Ltd. All rights reserved.