A "normal coupling" means a coupling where the direction of energy flow between the busbar sections is not defined. A directional coupling, however, means that the direction of energy flow between the busbar sections is defined. It can be used for mapping combinations of normal and safety power supply (e.g. between transformer and generator networks). The coupling is designed in compliance with IEC 60364-6.

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In order to add a directional coupling with a defined direction of energy flow that maps an emergency network, the cursor must be placed at one of the inner insert points of the busbar of the infeed circuit (i.e. not at its end), after the icon for adding a coupling has been enabled.

In order to add a normal coupling with an undefined direction of energy flow that maps a normal power supply network, the cursor must be placed on one of the insert points at the outer ends of the busbar shown for the infeed circuit.

The following input dialog for the selection of an infeed which is connected to the network through the coupling provides the option to select identical types of infeed or different ones.

A directional coupling is a changeover unit for supplying safety-relevant consumers. These units require in compliance with DIN VDE 0100 - 710 (IEC 60364-7-710, modified) section 710.537.6.1 that the tie breaker is installed in the main distribution board of the safety power supply system. In compliance with DIN VDE 0100-430 (IEC 60364-4-43), the switch at the beginning of of this changeover unit serves for the short-circuit protection of this connection between the normal distribution system and the distribution system for safety power supply.

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Active switchover takes place at the infeed level, passive switchover takes place at the sub-distribution level.