Protection against fire due to earth faults

The great majority of electrical short-circuit in low voltage installation are line to earth insulation failure.

The protective measures against electric shock presented in previous section of this chapter will ensure automatic disconnection of the supply in case of fault between a line conductor and accessible conductive part that could lead to dangerous touch voltages.

But fault between a line conductor and earth with lower amplitude than cable overcurrent protection threshold (and no risk of “indirect contact”) may also happen (see Figure F73).

Fig. F73 – Overcurrent protection curve and earth fault potential current