Protection against Indirect Contact
Indirect contact is the contact of persons or livestock with exposed conductive parts or extraneous conductive parts, which have become live under fault conditions.
Electric shocks due to indirect contact can occur if a person touches the metal casing of an appliance, or extraneous metalwork, which should not normally be live, but has become live due to a fault.
Shocks from non current carrying metalwork to earth:
In the event of a break in a protective conductor, the frame of an appliance will be disconnected from earth. This fault is unlikely to be noticed until a second fault occurs from the phase conductor to the frame. The frame will become live relative to earth and this will result in an electric shock being received by a person touching the frame. See Figure 13.
If the protective conductor is intact, and a fault occurs from the phase conductor to the frame, the frame will not become live. The fault current will flow to earth and a protective device will operate. A person touching the frame will not receive an electric shock. See Figure 14.
