Grounding is one of the most important safety factors of any electrical system and solar PV is no different than the other electrical system, So it is also important to ground the PV modules. This article is concerned about how grounding of modules will help to increase the quality life.
There is an electrical voltage between the PV cell and the frame and it can cause electrons come loose from the material used in the PV module and discharge through grounded frame. This causes a polarization that can adversely alter the characteristic curve of the PV cells. It leads to deterioration of the cells which is called as Bar Corrosion (It looks like bar codes).
Most of the PV panels are made of P-type cells which lead to polarization and negative potential is generated which are neutralized through the grounding negative array pole. If the array cannot be grounded because of the inverter used or if the modules are already polarized then the neutralization is done through specially manufactured devices such as SMA has recently developed a PVO box which neutralizes the reverse voltage.
When a PV module generates electricity its surface area becomes charged and acts like a capacitor. This capacitance has an undesirable effect and known as parasitic capacitance. During the operation of the PV module it is also connected to the inverter where the fluctuating voltage constantly changes the state of charge of parasitic capacitor and causes a displacement current proportional to the capacitance and to the voltage amplitude. This leads to a leakage current. This leakage current is not dangerous, however, it superimposes possible residual current that could occur through touching a live line through a damaged insulation and can seriously hinder its detection. Hence, grounding of SPV modules and inverter becomes very important. Most of the inverter manufactures provide negative and positive grounding option depending upon PV module connecting to an inverter. For example, A Sun power module requires a positive grounding. While a CdTe or Amorphous Silicon module requires a negative grounding. The positive and negative grounding depends that how modules top surface is charged.
Dr. Sanjay Vashishtha and Er. Gaurav Sharma