The automatic disconnection for TN system is achieved by overcurrent protective devices or RCDs

In this system all exposed and extraneous-conductive-parts of the installation are connected directly to the earthed point of the power supply by protective conductors.

As noted in Definition of standardised earthing schemes, the way in which this direct connection is carried out depends on whether the TN-C, TN-S, or TN-C-S method of implementing the TN principle is used. In Figure F18 the method TN-C is shown, in which the neutral conductor acts as both the Protective-Earth and Neutral (PEN) conductor. In all TN systems, any insulation fault to earth results in a phase to neutral short-circuit. High fault current levels allow to use overcurrent protection but can give rise to touch voltages exceeding 50 % of the phase to neutral voltage at the fault position during the short disconnection time.

In practice for utility distribution network, earth electrodes are normally installed at regular intervals along the protective conductor (PE or PEN) of the network, while the consumer is often required to install an earth electrode at the service entrance.