[1] The cause of the harmful leakage currents, besides the structure of the solar cell, is the voltage of the individual photovoltaic (PV) modules to the ground.
The degradation mechanism known as polarization found in the first generation crystalline silicon high performance modules from SunPower in strings having positive voltage potential with respect to ground was discussed in 2005.
PID was further discussed as a problem in ordinary crystalline modules (Photon 12/2010, lecture by solar energy company Solon SE at PVSEC in Valencia 2010).
The phenomenon does not affect photovoltaic installations with micro-inverters, as the voltages are too low to facilitate Potential Induced Degradation.
Seven companies, ELETTROGRAF/ATEX , Huawei, OriSolar, VIGDU, iLumen, PADCON and Pidbull have made a device that can prevent and reverse this effect.