Modelling of insulation characteristics of Solar Photovoltaic (SPV) modules

Dry and wet insulation characteristics of a Solar Photovoltaic (SPV) module have been studied through theoretical modelling supported by experimental results. A new equivalent circuit model approach has been used to understand the effect of resistances of the individual material used in the SPV module and the overall impact on the insulation characteristics. The electrical resistances of all the individual material have also been measured separately prior to lamination. It has been seen that, post lamination, the characteristics change significantly. EVA (Ethyl Vinyl Acetate) and Back-sheet (Tedlar) looses their separate identity and exhibit properties of a different new combined material. The resistance of this material has been determined using the equivalent circuit modelling approach. It has been shown that the insulation behaviour is primarily governed by this material. The temperature characteristics of the insulation leakage currents follow Arrhenius behaviour with well defined activation energies. It has been determined from the activation energies that the primary leakage path is from cell to EVA-Tedlar to frame of the module.