2. Different PID scaling levels

2.1 System level

The most important factor for the PID is the potential difference between the cell and the frame. System voltage depends on the number of modules connected in series, as well as on temperature and irradiation.

This potential difference is linked to the position of the modules connected in series in the string, and to the type of grounding. Three configurations are possible: positive polarity grounding, negative polarity grounding and no grounding. The potential of a chain has the same polarity with positive and negative grounding, as shown in figure 2