New design based on the original public domain image that was created and uploaded by Markus Kuhn. The original was simply incorrect, depicting separate N and PE to shared supply, this correctly shows shared PEN right to the equipment.

This diagram represents one of the earthing system arrangements defined by the IEC 60364-1 standard.

Only the star-configuration, AC, three-phase four-wire conductor arrangement is shown. It should be understood that not all installations will have a connection to every distribution conductor (Some three-phase installations may not connect to the neutral; Single-phase installations will only connect to one of the three line conductors). Three-phase three-wire distribution will not include a neutral (Non-existent from a delta configuration on the transformer secondary; Optional for distribution in the IT earthing system case with star configuration).

To give a broad overview of the diagram: The box at the top-left, as labelled, represents a generator or transformer, with the curved lines depicting transformer coils. The horizontal lines at the top represent the distribution system. The vertical lines coming down from them represent the supply connection to an individual property/installation. The dashed box with the label 'Consumer installation' beneath it represents an individual property/building and its electrical installation as a whole. The set of 'dots' (connection points) just within the dashed box represent where the external supply has entered the property and is connected to the installation. (The dot on the far right in the TT and TN systems is the 'main earthing terminal'). The solid box labelled 'Equipment' represents an example item of equipment within the installation. This equipment includes items such as sockets and light fittings, along with appliances ('loads') of either 'fixed' nature (e.g. shower; cooker; boiler; machinery), or more portable and pluggable nature (e.g. hair dryer; kettle; television). (Note that in the TN-C system case the link between neutral and earth would likely take place at a socket rather than in each appliance).

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