Electrical and Mechanical Insulation

The encapsulation system has to be able to withstand voltage differences at least as large as the system voltages. Metal frames must also be earthed, as internal and terminal potentials can be well above the earth potential. Any leakage currents to earth must be low to prevent interference with earth leakage safety devices. Some countries do not require the frames to be earthed (grounded). The practice is controversial as if the frame is grounded and a ground fault occurs it can cause arcing and a fire.

Solar modules must have adequate strength and rigidity to allow normal handling before and during installation. If glass is used for the top surface, it must be tempered, since the central areas of the module become hotter than areas near the frame. This places tension at the edges, and can cause cracking. In an array, the modules must be able to accommodate some degree of twisting in the mounting structure, need to be spaced with a small gap so that they can expand when heated up, and must withstand wind induced vibrations and the loads imposed by high winds, snow and ice.

Possible module twisting on a distorted mounting frame 1.

The standards set by the Australian Standards AS 4509-1999 include:

  1. Static load - 3.9 kPa for 1 hour front then back (equivalent to 200 km/hr winds).
  2. Dynamic load - 2.5 kPa front then back over 2,500 - 10,000 cycles (160 km/hr winds).
  3. Hail impact damage - 2.5 cm diameter ice ball at terminal velocity 23.2 m/s (~ 80 km/hr).
  • 1. Citekey JPL1981 not found